CVE-2026-23406

HIGHNVD 7.87.8
EchelonGraph scoreMEDIUM confidence

“—” beside the score: it is equal to NVD's CVSS score.

Score 7.8 from GitHub Security Advisory (severity: HIGH) published 2026-04-01. NVD baseline CVSS 7.8; sources differ by 0.0.

Triggered by: GitHub Security Advisory CVSS
Sources: EPSS, GitHub Security Advisory, NVD CVSS v3
Trending — 4 sources updated this week

Also known asEUVD-2026-17834 (ENISA EUVD) · GHSA-56hx-r887-5w6h (GitHub Security Advisories)Source: ENISA EUVD

7.8EG
EchelonGraph verdictPlan a fixRemediate within your standard update timelines (the SSVC decision on this page).
  • High severity, but no confirmed exploitation yet
CISA-KEV: Not listedEPSS PROB: 0.2%CVSS: 7.8Exploit: None knownExposed services: Not assessed

A fix is available — apply it.

In the Linux kernel, the following vulnerability has been resolved:

apparmor: fix side-effect bug in match_char() macro usage

The match_char() macro evaluates its character parameter multiple times when traversing differential encoding chains. When invoked with *str++, the string pointer advances on each iteration of the inner do-while loop, causing the DFA to check different characters at each iteration and therefore skip input characters. This results in out-of-bounds reads when the pointer advances past the input buffer boundary.

[ 94.984676] ================================================================== [ 94.985301] BUG: KASAN: slab-out-of-bounds in aa_dfa_match+0x5ae/0x760 [ 94.985655] Read of size 1 at addr ffff888100342000 by task file/976

[ 94.986319] CPU: 7 UID: 1000 PID: 976 Comm: file Not tainted 6.19.0-rc7-next-20260127 #1 PREEMPT(lazy) [ 94.986322] Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.16.3-debian-1.16.3-2 04/01/2014 [ 94.986329] Call Trace: [ 94.986341] [ 94.986347] dump_stack_lvl+0x5e/0x80 [ 94.986374] print_report+0xc8/0x270 [ 94.986384] ? aa_dfa_match+0x5ae/0x760 [ 94.986388] kasan_report+0x118/0x150 [ 94.986401] ? aa_dfa_match+0x5ae/0x760 [ 94.986405] aa_dfa_match+0x5ae/0x760 [ 94.986408] __aa_path_perm+0x131/0x400 [ 94.986418] aa_path_perm+0x219/0x2f0 [ 94.986424] apparmor_file_open+0x345/0x570 [ 94.986431] security_file_open+0x5c/0x140 [ 94.986442] do_dentry_open+0x2f6/0x1120 [ 94.986450] vfs_open+0x38/0x2b0 [ 94.986453] ? may_open+0x1e2/0x2b0 [ 94.986466] path_openat+0x231b/0x2b30 [ 94.986469] ? __x64_sys_openat+0xf8/0x130 [ 94.986477] do_file_open+0x19d/0x360 [ 94.986487] do_sys_openat2+0x98/0x100 [ 94.986491] __x64_sys_openat+0xf8/0x130 [ 94.986499] do_syscall_64+0x8e/0x660 [ 94.986515] ? count_memcg_events+0x15f/0x3c0 [ 94.986526] ? srso_alias_return_thunk+0x5/0xfbef5 [ 94.986540] ? handle_mm_fault+0x1639/0x1ef0 [ 94.986551] ? vma_start_read+0xf0/0x320 [ 94.986558] ? srso_alias_return_thunk+0x5/0xfbef5 [ 94.986561] ? srso_alias_return_thunk+0x5/0xfbef5 [ 94.986563] ? fpregs_assert_state_consistent+0x50/0xe0 [ 94.986572] ? srso_alias_return_thunk+0x5/0xfbef5 [ 94.986574] ? arch_exit_to_user_mode_prepare+0x9/0xb0 [ 94.986587] ? srso_alias_return_thunk+0x5/0xfbef5 [ 94.986588] ? irqentry_exit+0x3c/0x590 [ 94.986595] entry_SYSCALL_64_after_hwframe+0x76/0x7e [ 94.986597] RIP: 0033:0x7fda4a79c3ea

Fix by extracting the character value before invoking match_char, ensuring single evaluation per outer loop.

CVSS v3
7.8
EG Score
7.8HIGHmedium confidence
EG Risk
35
EG Risk 35/100

EG Risk is EchelonGraph's 0–100 priority score. It fuses impact severity (EG Severity, the CVSS base score, never the KEV-floored or EPSS-lifted EG Score) with real-world exploitation and automatability, under weights EchelonGraph set by hand, so you can rank equal-severity CVEs and fix the most dangerous first. Higher = act sooner.

How it’s computed (value × EchelonGraph’s weight)
Severity78% × 45%
Impact severity (EG Severity): CVSS 7.8 of 10. Never the KEV-floored or EPSS-lifted EG Score.
Exploitation0.2% × 40%
FIRST EPSS: the 30-day exploitation probability when EchelonGraph scored this CVE.
Automatability0% × 15%
CISA's BOD 26-04 default: no one has published Automatable for this CVE, and CISA treats it as “no” for a CVE not in KEV.
SSVC (CISA's decision table, applied by EchelonGraph): Track at low or medium mission impact; Track* at high (mission-essential systems).
Exploitation none (no CISA value, KEV listing or exploit code on record) · Automatable no (CISA's BOD 26-04 default) · Technical impact total (CISA's BOD 26-04 default). EchelonGraph holds no SSVC assessment of this CVE from CISA: none of these inputs is from Vulnrichment. EchelonGraph applied CISA's decision table to them; CISA publishes SSVC inputs and the table, not a decision for each CVE.
Action: A fix is available. Apply it within your standard update timelines.
EPSS PROB
0.2%
EPSS %ILE
8th
KEV
Not listed

What the EG score is made of (scorer v4.0: the three questions the 0–10 score mixes, published apart · methodology)

The EG score (7.8): severity, escalated by confirmed exploitation. This CVE's 7.8 is its impact severity (EG Severity), not escalated.

EG Severity
7.8 HIGHCVSS-B, impact only: no KEV listing, EPSS or EG-KEV tier raises it.GitHub Security Advisory CVSS
EG Likelihood
0.2% within 30 daysSource: FIRST EPSS. FIRST's exploitation probability, not an EchelonGraph model.
Confirmed exploitation
None on record (CISA KEV, EG-KEV Tier 1)Reported apart from the likelihood: an observed fact, not a probability.
EG Priority
SSVC Track at medium mission impactTrack at low or medium mission impact; Track* at high (mission-essential systems).CISA BOD 26-04: 14 days if the affected system is publicly exposed; Fix on system upgrade if it is not.Each input and its source: the SSVC and BOD 26-04 blocks below.

SSVC (CISA's decision table, applied by EchelonGraph)Track at low or medium mission impact; Track* at high (mission-essential systems).

A fix is available. Apply it within your standard update timelines.

Exploitation none (no CISA value, KEV listing or exploit code on record) · Automatable no (CISA's BOD 26-04 default) · Technical impact total (CISA's BOD 26-04 default). EchelonGraph holds no SSVC assessment of this CVE from CISA: none of these inputs is from Vulnrichment. EchelonGraph applied CISA's decision table to them; CISA publishes SSVC inputs and the table, not a decision for each CVE. Mission impact is CISA's Mission & Well-being decision point, and only you can judge it. CISA's table makes it high when Mission Prevalence is Essential — the vulnerable component "directly provides capabilities that constitute at least one MEF for at least one entity" (MEF: mission essential function) — or when Public Well-Being Impact is Irreversible: "multiple fatalities are likely", the cyber-physical system "is likely lost or destroyed", "extreme or serious externalities" are imposed on other parties, or social systems such as elections or the financial grid "are destabilized and potentially collapse". CISA's decision table

BOD 26-04 (CISA's remediation timeline, Table 1)14 days if the affected system is publicly exposed; Fix on system upgrade if it is not.

In CISA KEV no (CISA's KEV catalog) · Automatable no (CISA's BOD 26-04 default) · Technical impact total (CISA's BOD 26-04 default). Where an input reads “CISA's BOD 26-04 default”, no one has published it for this CVE, and CISA's implementation guidance says: “If “Automatable” and “Technical Impact” information items about a CVE ID are not available and the CVE ID is not in the KEV Catalog, CISA will treat its values as “no” and “total,” respectively, until CISA or a third party provides metadata about the CVE ID. CISA will always provide the Vulnrichment data for a CVE ID listed in the KEV Catalog.” Whether your system is publicly exposed is yours to answer. BOD 26-04 binds US Federal Civilian Executive Branch agencies; for anyone else it is CISA's published timeline, a reference rather than an obligation. The directive · how EchelonGraph applies it

Published

April 1, 2026

Last Modified

August 5, 2026

Advisory Details (8)

Auto-updated Jun 10, 2026
Patch available.
Web page

apparmor: fix side-effect bug in match_char() macro usage - kernel/git/stable/linux.git - Linux kernel stable tree

https://git.kernel.org/stable/c/f16f2e5936c0f5f0d11fdf10d2be3e47e7108e42
Web page

apparmor: fix side-effect bug in match_char() macro usage - kernel/git/stable/linux.git - Linux kernel stable tree

https://git.kernel.org/stable/c/c7dc56d8b37eda1396feeec3ab1c7ecee5eae31b
Web page

apparmor: fix side-effect bug in match_char() macro usage - kernel/git/stable/linux.git - Linux kernel stable tree

https://git.kernel.org/stable/c/b73c1dff8a9d7eeaebabf8097a5b2de192f40913
Web page

apparmor: fix side-effect bug in match_char() macro usage - kernel/git/stable/linux.git - Linux kernel stable tree

https://git.kernel.org/stable/c/8756b68edae37ff546c02091989a4ceab3f20abd
Web page

apparmor: fix side-effect bug in match_char() macro usage - kernel/git/stable/linux.git - Linux kernel stable tree

https://git.kernel.org/stable/c/5a184f7cbdeaad17e16dedf3c17d0cd622edfed8
Web page

apparmor: fix side-effect bug in match_char() macro usage - kernel/git/stable/linux.git - Linux kernel stable tree

https://git.kernel.org/stable/c/383b7270faf42564f133134c2fc3c24bbae52615
Web page

apparmor: fix side-effect bug in match_char() macro usage - kernel/git/stable/linux.git - Linux kernel stable tree

https://git.kernel.org/stable/c/1fc94f16098213d01e56c97feed9b3ecf0147a37
Web page

apparmor: fix side-effect bug in match_char() macro usage - kernel/git/stable/linux.git - Linux kernel stable tree

https://git.kernel.org/stable/c/0510d1ba0976f97f521feb2b75b0572ea5df3ceb

Vendor Advisories for CVE-2026-23406(1)

These vendors published their own advisory mentioning this CVE — often with vendor-specific remediation steps + affected product lists not in NVD.

Patch Availability(11)

Patches are aggregated from vendor advisories (Red Hat, Microsoft, Cisco, GitHub) and package ecosystems (OSV, GHSA). Multiple rows for the same upstream release have been deduplicated.

Affected Packages

(4 across 4 ecosystems)
Debian:11(1)
PackageVulnerable rangeFix by version rangeDependents
linux5.10.103-1 ... 5.10.92-2 (49 versions)
  • every version up to 5.10.251-1: fixed in 5.10.251-1
—
Debian:12(1)
PackageVulnerable rangeFix by version rangeDependents
linux6.1.106-1 ... 6.1.99-1 (47 versions)
  • every version up to 6.1.164-1: fixed in 6.1.164-1
—
Debian:13(1)
PackageVulnerable rangeFix by version rangeDependents
linux6.12.38-1 ... 6.12.74-2~bpo12+1 (15 versions)
  • every version up to 6.12.74-2: fixed in 6.12.74-2
—
Debian:14(1)
PackageVulnerable rangeFix by version rangeDependents
linux6.12.100-1 ... 6.19~rc8-1~exp1 (119 versions)
  • every version up to 6.19.6-2: fixed in 6.19.6-2
—

Weakness Classification(1)

MITRE Common Weakness Enumeration — the root-cause categories this CVE belongs to.

Additional Vendor Advisories

(10)

Data Freshness Timeline

(refreshed 10× in last 7d / 39× in last 30d)

Each row is a time one of our pipelines fetched, updated or re-scored this CVE. For example, "NVD update" means NVD published or revised its analysis for this CVE; "MITRE cvelistV5" means we ingested or refreshed it from the CNA feed. An arrow marks a change the record states ("CVSS v3 → 9.1"); EPSS and GHSA rows show the values recorded at that time, not what changed (EPSS values are rounded; hover one for the exact figures). Most recent first.

Showing the most recent 99 of 273 refreshes on record for this CVE.

A repeat, a row identical to one the same pipeline wrote less than 10 seconds earlier, is not a separate refresh and is not counted. 1 repeat row among the latest 100 is merged into the row it repeats. The 174 oldest rows on record are not shown and were not checked, so the counts can still include repeats.

  1. 2026-10-29 16:32 UTCEPSS rescoreEPSS 0.2% · 8th percentile
  2. 2026-10-28 16:31 UTCEPSS rescoreEPSS 0.2% · 7th percentile
  3. 2026-10-27 16:31 UTCEPSS rescoreEPSS 0.2% · 7th percentile
  4. 2026-10-26 16:31 UTCEPSS rescoreEPSS 0.2% · 7th percentile
  5. 2026-10-25 16:32 UTCEPSS rescoreEPSS 0.2% · 7th percentile
  6. 2026-10-25 14:41 UTCEG score recompute
  7. 2026-10-24 21:02 UTCEG score recompute
  8. 2026-10-24 21:02 UTCVendor advisory
  9. 2026-10-24 21:02 UTCGHSA enrichmentGHSA-56hx-r887-5w6h · GitHub severity HIGH · GitHub CVSS 7.8
  10. 2026-10-24 16:32 UTCEPSS rescoreEPSS 0.2% · 6th percentile
  11. 2026-10-22 16:34 UTCEPSS rescoreEPSS 0.2% · 6th percentile
  12. 2026-10-21 16:32 UTCEPSS rescoreEPSS 0.2% · 6th percentile
  13. 2026-10-20 16:32 UTCEPSS rescoreEPSS 0.2% · 6th percentile
  14. 2026-10-19 16:31 UTCEPSS rescoreEPSS 0.2% · 6th percentile
  15. 2026-10-18 16:31 UTCEPSS rescoreEPSS 0.2% · 6th percentile
  16. 2026-10-18 03:54 UTCEG score recompute
  17. 2026-10-17 17:08 UTCEG score recompute
  18. 2026-10-17 17:08 UTCVendor advisory
  19. 2026-10-17 17:07 UTCGHSA enrichmentGHSA-56hx-r887-5w6h · GitHub severity HIGH · GitHub CVSS 7.8
  20. 2026-10-17 16:33 UTCEPSS rescoreEPSS 0.2% · 6th percentile
  21. 2026-10-16 16:41 UTCEPSS rescoreEPSS 0.2% · 6th percentile
  22. 2026-10-15 16:31 UTCEPSS rescoreEPSS 0.2% · 6th percentile
  23. 2026-10-14 16:32 UTCEPSS rescoreEPSS 0.2% · 6th percentile
  24. 2026-10-13 16:33 UTCEPSS rescoreEPSS 0.2% · 6th percentile
  25. 2026-10-12 16:21 UTCEG score recompute
Show 74 more
  1. 2026-10-11 20:03 UTCEG score recompute
  2. 2026-10-11 17:16 UTCEG score recompute
  3. 2026-10-11 14:48 UTCEG score recompute
  4. 2026-10-11 13:48 UTCEPSS rescoreEPSS 0.2% · 6th percentile
  5. 2026-10-11 02:31 UTCOSV refresh
  6. 2026-10-10 20:00 UTCEPSS rescoreEPSS 0.2% · 6th percentile
  7. 2026-10-09 20:07 UTCEPSS rescoreEPSS 0.2% · 6th percentile
  8. 2026-10-08 17:11 UTCEPSS rescoreEPSS 0.2% · 6th percentile
  9. 2026-10-07 23:47 UTCEPSS rescoreEPSS 0.2% · 6th percentile
  10. 2026-10-06 15:17 UTCEPSS rescoreEPSS 0.2% · 6th percentile
  11. 2026-10-05 17:42 UTCEPSS rescoreEPSS 0.2% · 6th percentile
  12. 2026-10-04 23:21 UTCEPSS rescoreEPSS 0.2% · 6th percentile
  13. 2026-10-01 19:49 UTCEPSS rescoreEPSS 0.2% · 6th percentile
  14. 2026-09-30 15:03 UTCEPSS rescoreEPSS 0.2% · 6th percentile
  15. 2026-09-29 15:21 UTCEPSS rescoreEPSS 0.2% · 6th percentile
  16. 2026-09-28 13:51 UTCEPSS rescoreEPSS 0.2% · 6th percentile
  17. 2026-09-27 13:47 UTCEPSS rescoreEPSS 0.2% · 6th percentile
  18. 2026-09-26 15:58 UTCEPSS rescoreEPSS 0.2% · 6th percentile
  19. 2026-09-26 00:26 UTCEPSS rescoreEPSS 0.2% · 6th percentile
  20. 2026-09-24 14:03 UTCEPSS rescoreEPSS 0.2% · 6th percentile
  21. 2026-09-21 14:19 UTCOSV refresh
  22. 2026-09-20 20:15 UTCEPSS rescoreEPSS 0.2% · 7th percentile
  23. 2026-09-18 19:27 UTCEPSS rescoreEPSS 0.2% · 7th percentile
  24. 2026-09-16 14:07 UTCEPSS rescoreEPSS 0.2% · 7th percentile
  25. 2026-09-16 05:15 UTCEPSS rescoreEPSS 0.2% · 7th percentile
  26. 2026-09-13 16:47 UTCEPSS rescoreEPSS 0.2% · 7th percentile
  27. 2026-09-12 15:01 UTCEPSS rescoreEPSS 0.2% · 7th percentile
  28. 2026-09-11 14:52 UTCEPSS rescoreEPSS 0.2% · 7th percentile
  29. 2026-09-10 09:34 UTCEPSS rescoreEPSS 0.2% · 7th percentile
  30. 2026-09-08 22:00 UTCEPSS rescoreEPSS 0.2% · 7th percentile
  31. 2026-09-07 16:01 UTCEPSS rescoreEPSS 0.2% · 7th percentile
  32. 2026-09-06 13:47 UTCEPSS rescoreEPSS 0.2% · 7th percentile
  33. 2026-09-04 05:06 UTCEPSS rescoreEPSS 0.2% · 7th percentile
  34. 2026-09-02 14:11 UTCEPSS rescoreEPSS 0.2% · 7th percentile
  35. 2026-09-02 11:44 UTCOSV refresh
  36. 2026-09-01 13:53 UTCEPSS rescoreEPSS 0.2% · 7th percentile
  37. 2026-09-01 04:39 UTCEPSS rescoreEPSS 0.2% · 7th percentile
  38. 2026-08-30 19:17 UTCEPSS rescoreEPSS 0.2% · 7th percentile
  39. 2026-08-30 01:22 UTCEPSS rescoreEPSS 0.2% · 7th percentile
  40. 2026-08-28 21:41 UTCEPSS rescoreEPSS 0.2% · 7th percentile
  41. 2026-08-27 14:25 UTCEPSS rescoreEPSS 0.2% · 7th percentile
  42. 2026-08-26 14:46 UTCEPSS rescoreEPSS 0.2% · 7th percentile
  43. 2026-08-25 13:48 UTCEPSS rescoreEPSS 0.2% · 7th percentile
  44. 2026-08-21 23:49 UTCEPSS rescoreEPSS 0.2% · 7th percentile
  45. 2026-08-20 22:55 UTCEPSS rescoreEPSS 0.2% · 7th percentile
  46. 2026-08-19 17:03 UTCEPSS rescoreEPSS 0.2% · 7th percentile
  47. 2026-08-18 13:48 UTCEPSS rescoreEPSS 0.2% · 7th percentile
  48. 2026-08-17 13:47 UTCEPSS rescoreEPSS 0.2% · 7th percentile
  49. 2026-08-16 14:56 UTCEPSS rescoreEPSS 0.2% · 7th percentile
  50. 2026-08-16 09:32 UTCEG score recompute
  51. 2026-08-16 09:32 UTCVendor advisory
  52. 2026-08-16 09:32 UTCGHSA enrichmentGHSA-56hx-r887-5w6h · GitHub severity HIGH · GitHub CVSS 7.8
  53. 2026-08-16 02:14 UTCEPSS rescoreEPSS 0.2% · 7th percentile
  54. 2026-08-15 01:30 UTCEPSS rescoreEPSS 0.2% · 7th percentile
  55. 2026-08-14 19:03 UTCVendor advisory
  56. 2026-08-14 19:03 UTCGHSA enrichmentGHSA-56hx-r887-5w6h · GitHub severity HIGH · GitHub CVSS 7.8
  57. 2026-08-14 05:57 UTCEG score recompute
  58. 2026-08-14 05:57 UTCVendor advisory
  59. 2026-08-14 05:57 UTCGHSA enrichmentGHSA-56hx-r887-5w6h · GitHub severity HIGH · GitHub CVSS 7.8
  60. 2026-08-13 22:00 UTCEPSS rescoreEPSS 0.2% · 7th percentile
  61. 2026-08-13 10:07 UTCVendor advisory
  62. 2026-08-13 10:07 UTCGHSA enrichmentGHSA-56hx-r887-5w6h · GitHub severity HIGH · GitHub CVSS 7.8
  63. 2026-08-12 20:14 UTCEG score recompute
  64. 2026-08-12 20:14 UTCVendor advisory
  65. 2026-08-12 20:14 UTCGHSA enrichmentGHSA-56hx-r887-5w6h · GitHub severity HIGH · GitHub CVSS 7.8
  66. 2026-08-12 13:50 UTCEPSS rescoreEPSS 0.2% · 7th percentile
  67. 2026-08-11 20:34 UTCEG score recompute
  68. 2026-08-11 20:34 UTCVendor advisory
  69. 2026-08-11 20:34 UTCGHSA enrichmentGHSA-56hx-r887-5w6h · GitHub severity HIGH · GitHub CVSS 7.8
  70. 2026-08-11 13:42 UTCEPSS rescoreEPSS 0.2% · 7th percentile
  71. 2026-08-11 03:34 UTCEG score recompute
  72. 2026-08-11 03:34 UTCVendor advisory
  73. 2026-08-11 03:34 UTCGHSA enrichmentGHSA-56hx-r887-5w6h · GitHub severity HIGH · GitHub CVSS 7.8
  74. 2026-08-11 00:00 UTCEPSS rescoreEPSS 0.2% · 7th percentile

Frequently asked(5)

What is CVE-2026-23406?
CVE-2026-23406 is a high-severity vulnerability; its CVE record was published on April 1, 2026. In the Linux kernel, the following vulnerability has been resolved: apparmor: fix side-effect bug in match_char() macro usage The match_char() macro evaluates its character parameter multiple times when traversing differential encoding chains. When invoked with *str++, the string pointer advances…
When was the CVE record for CVE-2026-23406 published?
The CVE record for CVE-2026-23406 was published on April 1, 2026. That is the record's publication date; the vulnerability itself may have been made public earlier. EchelonGraph's copy of the record carries a last-modified date of August 5, 2026; the record at its source may have been updated since.
Is CVE-2026-23406 actively exploited?
CVE-2026-23406 is not currently on CISA's Known Exploited Vulnerabilities catalog. FIRST EPSS estimates a 0.2% probability of exploitation in the next 30 days (8th percentile of EPSS-scored CVEs).
What is the CVSS score of CVE-2026-23406?
CVE-2026-23406 has a CVSS v3 base score of 7.8 (NVD).
How do I remediate CVE-2026-23406?
A fix for CVE-2026-23406 is available: update to the fixed version the vendor names in its advisory. The vendor advisories EchelonGraph has for CVE-2026-23406 are linked in the Vendor Advisories panel on this page.

Dependency Blast Radius

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