CVE-2026-23455

CRITICALPre-NVD 9.19.1
EchelonGraph scoreMEDIUM confidence

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

Score 9.1 from GitHub Security Advisory (severity: CRITICAL) published 2026-04-03. A secondary CVSS source baseline 9.1; sources differ by 0.0.

Triggered by: GitHub Security Advisory CVSS
Sources: EPSS, GitHub Security Advisory, a secondary CVSS source
Trending — 4 sources updated this week
9.1EG
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: 1.3%CVSS: 9.1Exploit: None knownExposed services: Not assessed

A fix is available — apply it.

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

netfilter: nf_conntrack_h323: check for zero length in DecodeQ931()

In DecodeQ931(), the UserUserIE code path reads a 16-bit length from the packet, then decrements it by 1 to skip the protocol discriminator byte before passing it to DecodeH323_UserInformation(). If the encoded length is 0, the decrement wraps to -1, which is then passed as a large value to the decoder, leading to an out-of-bounds read.

Add a check to ensure len is positive after the decrement.

CVSS v3
9.1
EG Score
9.1CRITICALmedium confidence
EG Risk
41
EG Risk 41/100

EG Risk is EchelonGraph's 0–100 priority score: it fuses intrinsic severity with real-world exploitation and automatability so you can rank equal-severity CVEs and fix the most dangerous first. Higher = act sooner. Distinct from the 0–10 EG Score (severity).

How it’s computed (value × EchelonGraph’s weight)
Severity91% × 45%
The EG Score, 9.1 of 10.
Exploitation1.3% × 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
1.3%
EPSS %ILE
70th
KEV
Not listed

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 3, 2026

Last Modified

October 15, 2026

Advisory Details (10)

Auto-updated Sep 15, 2026
Patch available.
Web page

netfilter: nf_conntrack_h323: check for zero length in DecodeQ931() - kernel/git/stable/linux.git - Linux kernel stable tree

https://git.kernel.org/stable/c/f173d0f4c0f689173f8cdac79991043a4a89bf66
Web page

netfilter: nf_conntrack_h323: check for zero length in DecodeQ931() - kernel/git/stable/linux.git - Linux kernel stable tree

https://git.kernel.org/stable/c/b652b05d51003ac074b912684f9ec7486231717b
Web page

netfilter: nf_conntrack_h323: check for zero length in DecodeQ931() - kernel/git/stable/linux.git - Linux kernel stable tree

https://git.kernel.org/stable/c/9d00fe7d6d7c5b5f1065a6e042b54f2e44bd6df8
Web page

netfilter: nf_conntrack_h323: check for zero length in DecodeQ931() - kernel/git/stable/linux.git - Linux kernel stable tree

https://git.kernel.org/stable/c/633e8f87dad32263f6a57dccdb873f042c062111
Web page

netfilter: nf_conntrack_h323: check for zero length in DecodeQ931() - kernel/git/stable/linux.git - Linux kernel stable tree

https://git.kernel.org/stable/c/f5e4f4e4cdb75ec36802059a94195a31f193da60
Web page

netfilter: nf_conntrack_h323: check for zero length in DecodeQ931() - kernel/git/stable/linux.git - Linux kernel stable tree

https://git.kernel.org/stable/c/495e97af9e7249ee02b72bb1d0848a6efc3700f4
Web page

netfilter: nf_conntrack_h323: check for zero length in DecodeQ931() - kernel/git/stable/linux.git - Linux kernel stable tree

https://git.kernel.org/stable/c/65fa92f79677858b14b9e4b7275f26639afe2710
Web page

netfilter: nf_conntrack_h323: check for zero length in DecodeQ931() - kernel/git/stable/linux.git - Linux kernel stable tree

https://git.kernel.org/stable/c/2121f5fbe88daff0f1fc5bc47d359426c74b86b0

Patch Availability(31)

Vendor / EcosystemFix (by version range) / PatchReleasedSource
ubuntulinux-tools-azure (4.15.0.1205.220~14.04.1) @ trusty2026-10-15ubuntu
ubuntulinux-virtual-hwe-16.04-edge (4.15.0.254.266~16.04.1) @ xenial2026-10-15ubuntu
ubuntulinux-virtual-lts-xenial (4.4.0.283.289) @ xenial2026-10-15ubuntu
ubuntulowlatency-4.4 (4.4.0-243) @ xenial2026-10-15ubuntu
ubuntulowlatency-5.4 (5.4.0-26) @ focal2026-10-15ubuntu
ubuntulinux-tools-nvidia-tegra-rt-6.8 (6.8.0-1029.30) @ noble2026-10-15ubuntu
ubuntulinux-xilinx-zynqmp (6.8.0.1032.33) @ noble2026-10-15ubuntu
ubuntulinux-tools-oracle-edge (5.15.0.1108.114~20.04.1) @ focal2026-10-15ubuntu
ubuntulinux-virtual (3.13.0.214.224) @ trusty2026-10-15ubuntu
ubuntulinux-tools-nvidia-hwe-24.04 (6.17.0-1026.26) @ noble2026-10-15ubuntu
ubuntulinux-tools-raspi-realtime-6.8 (6.8.0-2049.50) @ noble2026-10-15ubuntu
ubuntulinux-tools-realtime-hwe-24.04-edge (6.17.0-1017.19) @ questing2026-10-15ubuntu
ubuntulinux-tools-raspi-6.8 (6.8.0-1060.64) @ noble2026-10-15ubuntu
ubuntulinux-tools-fips-6.8 (6.8.0-134.134+fips1) @ noble2026-10-15ubuntu
ubuntulinux-tools-raspi-nolpae (5.15.0.1105.103) @ jammy2026-10-15ubuntu
ubuntulinux-tools-azure-fde-lts-24.04 (6.8.0-1062.69) @ noble2026-10-15ubuntu
redhatkernel-0:6.12.0-55.98.1.el10_02026-08-17redhat
redhatkernel-rt-0:3.10.0-1160.155.1.rt56.1307.el72026-07-17redhat
redhatkernel-0:3.10.0-1160.154.1.el72026-07-06redhat
redhatkernel-0:4.18.0-477.150.1.el8_82026-07-06redhat
redhatkernel-0:4.18.0-305.197.1.el8_42026-07-06redhat
redhatkernel-0:4.18.0-372.198.1.el8_62026-07-01redhat
redhatkernel-0:5.14.0-427.134.1.el9_42026-06-22redhat
redhatkernel-0:5.14.0-284.176.1.el9_22026-06-17redhat
redhatkernel-rt-0:5.14.0-284.176.1.rt14.461.el9_22026-06-17redhat
redhatkernel-0:5.14.0-570.120.1.el9_62026-06-11redhat
redhatkernel-0:4.18.0-553.126.1.el8_102026-05-28redhat
redhatkernel-0:5.14.0-687.12.1.el9_82026-05-28redhat
redhatkernel-0:6.12.0-211.18.1.el10_22026-05-28redhat
redhatkernel-rt-0:4.18.0-553.126.1.rt7.467.el8_102026-05-28redhat
linuxKernel @ 5.10.253 (fixes >=2.6.17)—osv

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

(5 across 4 ecosystems)
Debian:11(2)
PackageVulnerable rangeFix by version rangeDependents
linux5.10.103-1 ... 5.10.92-2 (53 versions)
  • every version up to 5.10.257-1: fixed in 5.10.257-1
—
linux-6.16.1.106-3~deb11u1 ... 6.1.164-1~deb11u1 (16 versions)
  • every version up to 6.1.170-1~deb11u1: fixed in 6.1.170-1~deb11u1
—
Debian:12(1)
PackageVulnerable rangeFix by version rangeDependents
linux6.1.106-1 ... 6.1.99-1 (48 versions)
  • every version up to 6.1.170-1: fixed in 6.1.170-1
—
Debian:13(1)
PackageVulnerable rangeFix by version rangeDependents
linux6.12.38-1 ... 6.12.85-1~bpo12+1 (17 versions)
  • every version up to 6.12.85-1: fixed in 6.12.85-1
—
Debian:14(1)
PackageVulnerable rangeFix by version rangeDependents
linux6.12.100-1 ... 6.19~rc8-1~exp1 (123 versions)
  • every version up to 6.19.10-1: fixed in 6.19.10-1
—

Weakness Classification(1)

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

Additional Vendor Advisories

(11)

Data Freshness Timeline

(refreshed 25× in last 7d / 40× 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 340 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 241 oldest rows on record are not shown and were not checked, so the counts can still include repeats.

  1. 2026-10-15 02:29 UTCEG score recompute
  2. 2026-10-15 02:29 UTCVendor advisory
  3. 2026-10-15 02:28 UTCGHSA enrichmentGHSA-gm78-p64f-gx97 · GitHub severity CRITICAL · GitHub CVSS 9.1
  4. 2026-10-15 01:32 UTCEG score recompute
  5. 2026-10-15 01:32 UTCVendor advisory
  6. 2026-10-15 01:32 UTCGHSA enrichmentGHSA-gm78-p64f-gx97 · GitHub severity CRITICAL · GitHub CVSS 9.1
  7. 2026-10-14 16:32 UTCEPSS rescoreEPSS 1.3% · 70th percentile
  8. 2026-10-14 11:18 UTCEG score recompute
  9. 2026-10-14 11:18 UTCVendor advisory
  10. 2026-10-14 11:18 UTCGHSA enrichmentGHSA-gm78-p64f-gx97 · GitHub severity CRITICAL · GitHub CVSS 9.1
  11. 2026-10-13 16:33 UTCEPSS rescoreEPSS 1.3% · 70th percentile
  12. 2026-10-13 10:11 UTCEG score recompute
  13. 2026-10-13 10:11 UTCVendor advisory
  14. 2026-10-13 10:10 UTCGHSA enrichmentGHSA-gm78-p64f-gx97 · GitHub severity CRITICAL · GitHub CVSS 9.1
  15. 2026-10-12 16:33 UTCEPSS rescoreEPSS 1.3% · 70th percentile
  16. 2026-10-12 16:21 UTCEG score recompute
  17. 2026-10-12 09:16 UTCVendor advisory
  18. 2026-10-12 09:16 UTCGHSA enrichmentGHSA-gm78-p64f-gx97 · GitHub severity CRITICAL · GitHub CVSS 9.1
  19. 2026-10-11 20:03 UTCEG score recompute
  20. 2026-10-11 17:16 UTCEG score recompute
  21. 2026-10-11 14:48 UTCEG score recompute
  22. 2026-10-11 13:48 UTCEPSS rescoreEPSS 1.3% · 70th percentile
  23. 2026-10-10 20:00 UTCEPSS rescoreEPSS 1.3% · 70th percentile
  24. 2026-10-09 20:07 UTCEPSS rescoreEPSS 1.3% · 70th percentile
  25. 2026-10-08 17:11 UTCEPSS rescoreEPSS 1.3% · 70th percentile
Show 74 more
  1. 2026-10-07 23:47 UTCEPSS rescoreEPSS 1.3% · 70th percentile
  2. 2026-10-06 15:17 UTCEPSS rescoreEPSS 1.3% · 70th percentile
  3. 2026-10-05 17:42 UTCEPSS rescoreEPSS 1.3% · 70th percentile
  4. 2026-10-01 19:49 UTCEPSS rescoreEPSS 1.3% · 70th percentile
  5. 2026-09-30 15:03 UTCEPSS rescoreEPSS 1.3% · 70th percentile
  6. 2026-09-29 15:21 UTCEPSS rescoreEPSS 1.3% · 70th percentile
  7. 2026-09-28 13:51 UTCEPSS rescoreEPSS 1.3% · 70th percentile
  8. 2026-09-28 00:49 UTCOSV refresh
  9. 2026-09-27 13:47 UTCEPSS rescoreEPSS 1.3% · 70th percentile
  10. 2026-09-26 15:58 UTCEPSS rescoreEPSS 1.3% · 70th percentile
  11. 2026-09-26 00:26 UTCEPSS rescoreEPSS 1.3% · 70th percentile
  12. 2026-09-24 14:03 UTCEPSS rescoreEPSS 1.3% · 70th percentile
  13. 2026-09-18 19:27 UTCEPSS rescoreEPSS 1.3% · 69th percentile
  14. 2026-09-16 14:07 UTCEPSS rescoreEPSS 1.3% · 69th percentile
  15. 2026-09-16 05:15 UTCEPSS rescoreEPSS 1.3% · 69th percentile
  16. 2026-09-13 16:47 UTCEPSS rescoreEPSS 1.3% · 69th percentile
  17. 2026-09-12 15:01 UTCEPSS rescoreEPSS 1.3% · 69th percentile
  18. 2026-09-11 14:52 UTCEPSS rescoreEPSS 1.3% · 69th percentile
  19. 2026-09-10 09:34 UTCEPSS rescoreEPSS 1.3% · 69th percentile
  20. 2026-09-08 22:00 UTCEPSS rescoreEPSS 1.3% · 69th percentile
  21. 2026-09-08 09:14 UTCEG score recompute
  22. 2026-09-08 09:14 UTCVendor advisory
  23. 2026-09-08 09:13 UTCGHSA enrichmentGHSA-gm78-p64f-gx97 · GitHub severity CRITICAL · GitHub CVSS 9.1
  24. 2026-09-07 16:01 UTCEPSS rescoreEPSS 1.3% · 69th percentile
  25. 2026-09-06 13:47 UTCEPSS rescoreEPSS 1.3% · 69th percentile
  26. 2026-09-04 05:06 UTCEPSS rescoreEPSS 1.3% · 69th percentile
  27. 2026-09-02 14:11 UTCEPSS rescoreEPSS 1.3% · 69th percentile
  28. 2026-09-02 11:14 UTCOSV refresh
  29. 2026-09-01 13:53 UTCEPSS rescoreEPSS 1.3% · 69th percentile
  30. 2026-09-01 04:39 UTCEPSS rescoreEPSS 1.3% · 69th percentile
  31. 2026-08-30 19:17 UTCEPSS rescoreEPSS 1.3% · 69th percentile
  32. 2026-08-30 01:22 UTCEPSS rescoreEPSS 1.3% · 68th percentile
  33. 2026-08-28 21:41 UTCEPSS rescoreEPSS 1.3% · 68th percentile
  34. 2026-08-27 14:25 UTCEPSS rescoreEPSS 1.3% · 69th percentile
  35. 2026-08-26 14:46 UTCEPSS rescoreEPSS 1.3% · 69th percentile
  36. 2026-08-25 13:48 UTCEPSS rescoreEPSS 1.3% · 69th percentile
  37. 2026-08-23 00:19 UTCEPSS rescoreEPSS 1.3% · 69th percentile
  38. 2026-08-21 23:49 UTCEPSS rescoreEPSS 1.3% · 69th percentile
  39. 2026-08-20 22:55 UTCEPSS rescoreEPSS 1.3% · 69th percentile
  40. 2026-08-19 17:03 UTCEPSS rescoreEPSS 1.3% · 68th percentile
  41. 2026-08-18 13:48 UTCEPSS rescoreEPSS 1.3% · 68th percentile
  42. 2026-08-17 13:47 UTCEPSS rescoreEPSS 1.3% · 68th percentile
  43. 2026-08-16 14:56 UTCEPSS rescoreEPSS 1.3% · 68th percentile
  44. 2026-08-16 09:17 UTCEG score recompute
  45. 2026-08-16 09:17 UTCVendor advisory
  46. 2026-08-16 09:17 UTCGHSA enrichmentGHSA-gm78-p64f-gx97 · GitHub severity CRITICAL · GitHub CVSS 9.1
  47. 2026-08-16 02:14 UTCEPSS rescoreEPSS 1.3% · 68th percentile
  48. 2026-08-15 01:30 UTCEPSS rescoreEPSS 1.3% · 68th percentile
  49. 2026-08-14 22:56 UTCVendor advisory
  50. 2026-08-14 22:56 UTCGHSA enrichmentGHSA-gm78-p64f-gx97 · GitHub severity CRITICAL · GitHub CVSS 9.1
  51. 2026-08-14 18:52 UTCVendor advisory
  52. 2026-08-14 18:52 UTCGHSA enrichmentGHSA-gm78-p64f-gx97 · GitHub severity CRITICAL · GitHub CVSS 9.1
  53. 2026-08-14 13:51 UTCVendor advisory
  54. 2026-08-14 13:51 UTCGHSA enrichmentGHSA-gm78-p64f-gx97 · GitHub severity CRITICAL · GitHub CVSS 9.1
  55. 2026-08-14 09:47 UTCVendor advisory
  56. 2026-08-14 09:47 UTCGHSA enrichmentGHSA-gm78-p64f-gx97 · GitHub severity CRITICAL · GitHub CVSS 9.1
  57. 2026-08-14 05:43 UTCEG score recompute
  58. 2026-08-14 05:43 UTCVendor advisory
  59. 2026-08-14 05:43 UTCGHSA enrichmentGHSA-gm78-p64f-gx97 · GitHub severity CRITICAL · GitHub CVSS 9.1
  60. 2026-08-13 22:00 UTCEPSS rescoreEPSS 1.3% · 68th percentile
  61. 2026-08-13 09:56 UTCVendor advisory
  62. 2026-08-13 09:56 UTCGHSA enrichmentGHSA-gm78-p64f-gx97 · GitHub severity CRITICAL · GitHub CVSS 9.1
  63. 2026-08-13 04:06 UTCVendor advisory
  64. 2026-08-13 04:06 UTCGHSA enrichmentGHSA-gm78-p64f-gx97 · GitHub severity CRITICAL · GitHub CVSS 9.1
  65. 2026-08-13 00:02 UTCVendor advisory
  66. 2026-08-13 00:02 UTCGHSA enrichmentGHSA-gm78-p64f-gx97 · GitHub severity CRITICAL · GitHub CVSS 9.1
  67. 2026-08-12 19:58 UTCEG score recompute
  68. 2026-08-12 19:58 UTCVendor advisory
  69. 2026-08-12 19:58 UTCGHSA enrichmentGHSA-gm78-p64f-gx97 · GitHub severity CRITICAL · GitHub CVSS 9.1
  70. 2026-08-12 13:50 UTCEPSS rescoreEPSS 1.3% · 68th percentile
  71. 2026-08-12 00:40 UTCVendor advisory
  72. 2026-08-12 00:39 UTCGHSA enrichmentGHSA-gm78-p64f-gx97 · GitHub severity CRITICAL · GitHub CVSS 9.1
  73. 2026-08-11 20:17 UTCEG score recompute
  74. 2026-08-11 20:17 UTCVendor advisory

Frequently asked(5)

What is CVE-2026-23455?
CVE-2026-23455 is a critical-severity vulnerability; its CVE record was published on April 3, 2026. In the Linux kernel, the following vulnerability has been resolved: netfilter: nfconntrackh323: check for zero length in DecodeQ931() In DecodeQ931(), the UserUserIE code path reads a 16-bit length from the packet, then decrements it by 1 to skip the protocol discriminator byte before passing it to…
When was the CVE record for CVE-2026-23455 published?
The CVE record for CVE-2026-23455 was published on April 3, 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 October 15, 2026; the record at its source may have been updated since.
Is CVE-2026-23455 actively exploited?
CVE-2026-23455 is not currently on CISA's Known Exploited Vulnerabilities catalog. FIRST EPSS estimates a 1.3% probability of exploitation in the next 30 days (70th percentile of EPSS-scored CVEs).
What is the CVSS score of CVE-2026-23455?
CVE-2026-23455 has a CVSS base score of 9.1 (a secondary CVSS source that NVD displays; NVD's own analysis pending).
How do I remediate CVE-2026-23455?
A fix for CVE-2026-23455 is available: update to the fixed version the vendor names in its advisory. The vendor advisories EchelonGraph has for CVE-2026-23455 are linked in the Vendor Advisories panel on this page.

Dependency Blast Radius

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