CVE-2026-23405

MEDIUMNVD 5.55.5—
EchelonGraph scoreMEDIUM confidence

Score 5.5 from GitHub Security Advisory published 2026-04-01. NVD baseline CVSS 5.5; sources differ by 0.0.

Triggered by: GitHub Security Advisory CVSS
Sources: epss, ghsa, nvd
5.5EG
EchelonGraph verdictMonitorLow exploitation likelihood right now — keep watching.
  • Lower severity and no public exploit yet
CISA-KEV: Not listedEPSS PROB: 0%CVSS: 5.5Exploit: None knownExposed: 0

A fix is available — apply it.

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

apparmor: fix: limit the number of levels of policy namespaces

Currently the number of policy namespaces is not bounded relying on the user namespace limit. However policy namespaces aren't strictly tied to user namespaces and it is possible to create them and nest them arbitrarily deep which can be used to exhaust system resource.

Hard cap policy namespaces to the same depth as user namespaces.

CVSS v3
5.5
EG Score
5.5(medium)
EG Risk
29(Track)
EG Risk 29/100SSVC: Track

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
Severity55% × 45%
Exploitation0% × 40%
Automatability30% × 15%
Action: Routine — remediate on your standard cadence.
EPSS PROB
0%
EPSS %ILE
8%
KEV
Not listed

Published

April 1, 2026

Last Modified

April 24, 2026

Advisory Details (8)

Auto-updated Aug 6, 2026
No patch confirmed yet.
generic

apparmor: fix: limit the number of levels of policy namespaces - kernel/git/stable/linux.git - Linux kernel stable tree

https://git.kernel.org/stable/c/d42b2b6bb77ca40ee34ab74ad79305840b5f315d
generic

apparmor: fix: limit the number of levels of policy namespaces - kernel/git/stable/linux.git - Linux kernel stable tree

https://git.kernel.org/stable/c/b1226e37eb3754d389721c135db6107db94c7a72
generic

apparmor: fix: limit the number of levels of policy namespaces - kernel/git/stable/linux.git - Linux kernel stable tree

https://git.kernel.org/stable/c/87d0cecc900e55d55fc4dbfb43ac93e269c7a5b3
generic

apparmor: fix: limit the number of levels of policy namespaces - kernel/git/stable/linux.git - Linux kernel stable tree

https://git.kernel.org/stable/c/853ce31ca72097d23991a06876a2ccb5cb64b603
generic

apparmor: fix: limit the number of levels of policy namespaces - kernel/git/stable/linux.git - Linux kernel stable tree

https://git.kernel.org/stable/c/7b6495ead2c611647f6b11441a852324e3eb8616
generic

apparmor: fix: limit the number of levels of policy namespaces - kernel/git/stable/linux.git - Linux kernel stable tree

https://git.kernel.org/stable/c/6b396cc2f0365e684fc1d3547d18ef79fcee225d
generic

apparmor: fix: limit the number of levels of policy namespaces - kernel/git/stable/linux.git - Linux kernel stable tree

https://git.kernel.org/stable/c/3f8699b3ee0c04b4b9bc27b82cd89a40e81e1d2e
generic

apparmor: fix: limit the number of levels of policy namespaces - kernel/git/stable/linux.git - Linux kernel stable tree

https://git.kernel.org/stable/c/306039414932c80f8420695a24d4fe10c84ccfb2

Vendor Advisories for CVE-2026-23405(1)

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

Patch Availability(13)

Vendor / EcosystemFixed in / PatchReleasedSource
ubuntulinux-tools-oem-6.17 (6.17.0-1017.17) @ noble2026-06-11ubuntu
ubuntulinux-tools-azure-lts-22.04 (5.15.0.1109.107) @ jammy2026-06-11ubuntu
ubuntulinux-tools-azure-edge (5.4.0.1161.167~18.04.1) @ bionic2026-06-11ubuntu
ubuntulinux-tools-bluefield-5.4 (5.4.0.1116.112) @ focal2026-06-11ubuntu
ubuntulinux-tools-intel-iot-realtime-5.15 (5.15.0.1096.100) @ jammy2026-06-11ubuntu
ubuntulinux-tools-azure-edge (5.15.0.1110.119~20.04.1) @ focal2026-06-11ubuntu
ubuntulinux-xilinx-zynqmp (6.8.0.1029.30) @ noble2026-06-11ubuntu
ubuntulinux-tools-azure-fips-5.15 (5.15.0.1109.94) @ jammy2026-06-11ubuntu
ubuntulinux-tools-oracle (4.15.0.1153.164~16.04.1) @ xenial2026-06-11ubuntu
ubuntulinux-virtual-hwe-16.04-edge (4.15.0.249.233) @ bionic2026-06-11ubuntu
ubuntulinux-tools-azure-fips-6.8 (6.8.0-1052.58+fips1) @ noble2026-06-11ubuntu
ubuntulinux-tools-raspi2-hwe-18.04-edge (5.4.0.1139.170) @ focal2026-06-11ubuntu
linuxKernel @ 5.10.253—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

(4 across 4 ecosystems)
Debian:11(1)
PackageVulnerable rangeFixed inDependents
linux5.10.103-1 ... 5.10.92-2 (49 versions)5.10.251-1—
Debian:12(1)
PackageVulnerable rangeFixed inDependents
linux6.1.106-1 ... 6.1.99-1 (47 versions)6.1.164-1—
Debian:13(1)
PackageVulnerable rangeFixed inDependents
linux6.12.38-1 ... 6.12.74-2~bpo12+1 (15 versions)6.12.74-2—
Debian:14(1)
PackageVulnerable rangeFixed inDependents
linux6.12.100-1 ... 6.19~rc8-1~exp1 (118 versions)6.19.6-2—

Additional Vendor Advisories

(12)

Vendors that published advisories for this CVE beyond the curated set above. Broader coverage but minimal per-row detail — click through for the original advisory.

Data Freshness Timeline

(refreshed 5× in last 7d / 29× in last 30d)

Each row is a source pipeline that fetched or updated this CVE on that date, with what changed. 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. Most recent first.

Showing the most recent 100 of 201 total refreshes for this CVE.

  1. 2026-09-13 16:47 UTCEPSS rescore
  2. 2026-09-12 15:01 UTCEPSS rescore
  3. 2026-09-11 14:52 UTCEPSS rescore
  4. 2026-09-10 09:34 UTCEPSS rescore
  5. 2026-09-08 22:00 UTCEPSS rescore
  6. 2026-09-07 16:01 UTCEPSS rescore
  7. 2026-09-06 13:47 UTCEPSS rescore
  8. 2026-09-06 13:47 UTCEPSS rescore
  9. 2026-09-04 05:06 UTCEPSS rescore
  10. 2026-09-02 14:11 UTCEPSS rescore
  11. 2026-09-02 11:44 UTCOSV refresh
  12. 2026-09-01 13:53 UTCEPSS rescore
  13. 2026-09-01 04:39 UTCEPSS rescore
  14. 2026-08-30 19:17 UTCEPSS rescore
  15. 2026-08-30 01:22 UTCEPSS rescore
  16. 2026-08-28 21:41 UTCEPSS rescore
  17. 2026-08-27 14:25 UTCEPSS rescore
  18. 2026-08-26 14:46 UTCEPSS rescore
  19. 2026-08-25 13:48 UTCEPSS rescore
  20. 2026-08-23 00:19 UTCEPSS rescore
  21. 2026-08-21 23:49 UTCEPSS rescore
  22. 2026-08-20 22:55 UTCEPSS rescore
  23. 2026-08-19 17:03 UTCEPSS rescore
  24. 2026-08-18 13:48 UTCEPSS rescore
  25. 2026-08-17 13:47 UTCEPSS rescore
Show 75 more
  1. 2026-08-16 14:56 UTCEPSS rescore
  2. 2026-08-16 09:32 UTCEG score recompute
  3. 2026-08-16 09:32 UTCVendor advisory
  4. 2026-08-16 09:32 UTCGHSA enrichment
  5. 2026-08-16 02:14 UTCEPSS rescore
  6. 2026-08-15 01:30 UTCEPSS rescore
  7. 2026-08-14 05:57 UTCEG score recompute
  8. 2026-08-14 05:57 UTCVendor advisory
  9. 2026-08-14 05:57 UTCGHSA enrichment
  10. 2026-08-13 22:00 UTCEPSS rescore
  11. 2026-08-12 23:58 UTCEG score recompute
  12. 2026-08-12 23:58 UTCVendor advisory
  13. 2026-08-12 23:58 UTCGHSA enrichment
  14. 2026-08-12 13:50 UTCEPSS rescore
  15. 2026-08-12 01:46 UTCEG score recompute
  16. 2026-08-12 01:46 UTCVendor advisory
  17. 2026-08-12 01:46 UTCGHSA enrichment
  18. 2026-08-11 13:42 UTCEPSS rescore
  19. 2026-08-11 03:34 UTCEG score recompute
  20. 2026-08-11 03:34 UTCVendor advisory
  21. 2026-08-11 03:34 UTCGHSA enrichment
  22. 2026-08-11 00:00 UTCEPSS rescore
  23. 2026-08-10 03:43 UTCEG score recompute
  24. 2026-08-10 03:43 UTCVendor advisory
  25. 2026-08-10 03:43 UTCGHSA enrichment
  26. 2026-08-09 13:46 UTCEPSS rescore
  27. 2026-08-09 05:31 UTCEG score recompute
  28. 2026-08-09 05:31 UTCVendor advisory
  29. 2026-08-09 05:31 UTCGHSA enrichment
  30. 2026-08-07 15:37 UTCEG score recompute
  31. 2026-08-07 15:37 UTCVendor advisory
  32. 2026-08-07 15:37 UTCGHSA enrichment
  33. 2026-08-06 13:46 UTCEPSS rescore
  34. 2026-08-06 00:31 UTCEG score recompute
  35. 2026-08-06 00:31 UTCVendor advisory
  36. 2026-08-06 00:31 UTCGHSA enrichment
  37. 2026-08-05 19:17 UTCEPSS rescore
  38. 2026-08-04 15:10 UTCEPSS rescore
  39. 2026-08-04 10:38 UTCEPSS rescore
  40. 2026-08-03 22:51 UTCEG score recompute
  41. 2026-08-03 22:51 UTCVendor advisory
  42. 2026-08-03 22:51 UTCGHSA enrichment
  43. 2026-08-03 10:35 UTCEPSS rescore
  44. 2026-08-02 14:51 UTCEG score recompute
  45. 2026-08-02 14:51 UTCVendor advisory
  46. 2026-08-02 14:51 UTCGHSA enrichment
  47. 2026-08-02 02:26 UTCEPSS rescore
  48. 2026-07-30 01:30 UTCEPSS rescore
  49. 2026-07-27 14:13 UTCEPSS rescore
  50. 2026-07-26 14:54 UTCEPSS rescore
  51. 2026-07-26 14:54 UTCEPSS rescore
  52. 2026-07-25 14:17 UTCEPSS rescore
  53. 2026-07-25 14:17 UTCEPSS rescore
  54. 2026-07-24 14:17 UTCEPSS rescore
  55. 2026-07-23 14:18 UTCEPSS rescore
  56. 2026-07-23 14:18 UTCEPSS rescore
  57. 2026-07-23 03:07 UTCEG score recompute
  58. 2026-07-22 14:08 UTCEPSS rescore
  59. 2026-07-21 15:24 UTCEPSS rescore
  60. 2026-07-21 15:24 UTCEPSS rescore
  61. 2026-07-20 17:08 UTCEPSS rescore
  62. 2026-07-19 14:31 UTCEPSS rescore
  63. 2026-07-19 14:31 UTCEPSS rescore
  64. 2026-07-19 02:29 UTCEPSS rescore
  65. 2026-07-19 02:28 UTCEPSS rescore
  66. 2026-07-18 10:04 UTCEPSS rescore
  67. 2026-07-18 10:04 UTCEPSS rescore
  68. 2026-07-17 04:24 UTCOSV refresh
  69. 2026-07-16 17:03 UTCEPSS rescore
  70. 2026-07-16 17:03 UTCEPSS rescore
  71. 2026-07-15 16:57 UTCEPSS rescore
  72. 2026-07-15 16:57 UTCEPSS rescore
  73. 2026-07-15 02:00 UTCEPSS rescore
  74. 2026-07-15 02:00 UTCEPSS rescore
  75. 2026-07-13 22:30 UTCEPSS rescore

Frequently asked(5)

What is CVE-2026-23405?
CVE-2026-23405 is a medium vulnerability published on April 1, 2026. In the Linux kernel, the following vulnerability has been resolved: apparmor: fix: limit the number of levels of policy namespaces Currently the number of policy namespaces is not bounded relying on the user namespace limit. However policy namespaces aren't strictly tied to user namespaces and it…
When was CVE-2026-23405 disclosed?
CVE-2026-23405 was first published in the National Vulnerability Database on April 1, 2026, with the most recent update on April 24, 2026. EchelonGraph re-ingests CVE updates from NVD on a 2-hour cycle, so this page reflects the latest published state.
Is CVE-2026-23405 actively exploited?
CVE-2026-23405 is not currently on CISA's Known Exploited Vulnerabilities catalog. FIRST EPSS estimates a 0% probability of exploitation in the next 30 days, which ranks it in the top 92.2% of all scored CVEs.
What is the CVSS score of CVE-2026-23405?
CVE-2026-23405 has a CVSS v3 base score of 5.5 (NVD).
How do I remediate CVE-2026-23405?
Patch to the fixed version published by the affected vendor. Where vendor advisories exist for CVE-2026-23405, EchelonGraph cross-links them in the Vendor Advisories panel below — those typically contain the canonical remediation steps, fixed version numbers, and any vendor-specific mitigations.

Dependency Blast Radius

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