CVE-2026-23455

CRITICALPre-NVD 9.19.1—
EchelonGraph scoreMEDIUM confidence

Score 9.1 from GitHub Security Advisory (severity: CRITICAL) published 2026-04-03. the CNA's CVSS baseline 9.1; sources differ by 0.0.

Triggered by: GitHub Security Advisory CVSS
Sources: cna:linux, epss, ghsa
9.1EG
EchelonGraph verdictPlan a fixSerious severity, but no confirmed exploitation yet.
  • High severity, but no confirmed exploitation yet
CISA-KEV: Not listedEPSS PROB: 1%CVSS: 9.1Exploit: None knownExposed: 0

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
9.1(medium)
EG Risk
46(Track)
EG Risk 46/100SSVC: 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
Severity91% × 45%
Exploitation1% × 40%
Automatability30% × 15%
Action: Routine — remediate on your standard cadence.
EPSS PROB
1%
EPSS %ILE
69%
KEV
Not listed

Published

April 3, 2026

Last Modified

August 5, 2026

Advisory Details (10)

Auto-updated Aug 29, 2026
No patch confirmed yet.
generic

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
generic

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
generic

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
generic

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
generic

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
generic

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
generic

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
generic

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
generic🔴 Active Exploitation

SSA-082556

https://cert-portal.siemens.com/productcert/html/ssa-082556.html
generic

SSA-019113

https://cert-portal.siemens.com/productcert/html/ssa-019113.html

Vendor Advisories for CVE-2026-23455(15)

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

Patch Availability(31)

Vendor / EcosystemFixed in / PatchReleasedSource
ubuntulinux-tools-realtime-hwe-24.04-edge (6.17.0-1017.19) @ questing2026-07-26ubuntu
ubuntulinux-tools-raspi-6.8 (6.8.0-1060.64) @ noble2026-07-26ubuntu
ubuntulinux-virtual-hwe-24.04 (6.17.0-40.40~24.04.1) @ noble2026-07-26ubuntu
ubuntulinux-tools-raspi-6.17 (6.17.0-1021.21) @ questing2026-07-26ubuntu
ubuntulinux-xilinx-zynqmp-tools-5.15.0-1074 (5.15.0-1074.78) @ jammy2026-07-26ubuntu
ubuntulinux-tools-nvidia-tegra-rt-6.8 (6.8.0-1029.30) @ noble2026-07-26ubuntu
ubuntulinux-tools-oracle-edge (5.15.0.1108.114~20.04.1) @ focal2026-07-26ubuntu
ubuntulinux-xilinx-zynqmp (6.8.0.1032.33) @ noble2026-07-26ubuntu
ubuntulinux-virtual (3.13.0.214.224) @ trusty2026-07-26ubuntu
ubuntulinux-tools-raspi-realtime-6.8 (6.8.0-2049.50) @ noble2026-07-26ubuntu
ubuntulinux-tools-nvidia-hwe-24.04 (6.17.0-1026.26) @ noble2026-07-26ubuntu
ubuntulinux-virtual-hwe-16.04-edge (4.15.0.253.237) @ bionic2026-07-26ubuntu
ubuntulinux-tools-aws-lts-18.04 (4.15.0.1194.192) @ bionic2026-07-26ubuntu
ubuntulinux-tools-fips-6.8 (6.8.0-134.134+fips1) @ noble2026-07-26ubuntu
ubuntulinux-tools-raspi-nolpae (5.15.0.1105.103) @ jammy2026-07-26ubuntu
ubuntulinux-tools-intel-iotg-edge (5.15.0.1106.112~20.04.1) @ focal2026-07-26ubuntu
ubuntulinux-tools-azure-fde-6.17 (6.17.0-1018.18~24.04.1) @ noble2026-07-26ubuntu
redhatkernel-rt-0:3.10.0-1160.155.1.rt56.1307.el72026-07-17redhat
redhatkernel-0:4.18.0-305.197.1.el8_42026-07-06redhat
redhatkernel-0:4.18.0-477.150.1.el8_82026-07-06redhat
redhatkernel-0:3.10.0-1160.154.1.el72026-07-06redhat
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-rt-0:5.14.0-284.176.1.rt14.461.el9_22026-06-17redhat
redhatkernel-0:5.14.0-284.176.1.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—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 rangeFixed inDependents
linux5.10.103-1 ... 5.10.92-2 (53 versions)5.10.257-1—
linux-6.16.1.106-3~deb11u1 ... 6.1.164-1~deb11u1 (16 versions)6.1.170-1~deb11u1—
Debian:12(1)
PackageVulnerable rangeFixed inDependents
linux6.1.106-1 ... 6.1.99-1 (48 versions)6.1.170-1—
Debian:13(1)
PackageVulnerable rangeFixed inDependents
linux6.12.38-1 ... 6.12.85-1~bpo12+1 (17 versions)6.12.85-1—
Debian:14(1)
PackageVulnerable rangeFixed inDependents
linux6.12.100-1 ... 6.19~rc8-1~exp1 (119 versions)6.19.10-1—

Weakness Classification(1)

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

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 6× in last 7d / 119× 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 285 total refreshes for this CVE.

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

Related CVEs(same product + same vendor + same CWE)

Frequently asked(5)

What is CVE-2026-23455?
CVE-2026-23455 is a critical vulnerability 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 CVE-2026-23455 disclosed?
CVE-2026-23455 was first published in the National Vulnerability Database on April 3, 2026, with the most recent update on August 5, 2026. EchelonGraph re-ingests CVE updates from NVD on a 2-hour cycle, so this page reflects the latest published state.
Is CVE-2026-23455 actively exploited?
CVE-2026-23455 is not currently on CISA's Known Exploited Vulnerabilities catalog. FIRST EPSS estimates a 1% probability of exploitation in the next 30 days, which ranks it in the top 30.8% of all scored CVEs.
What is the CVSS score of CVE-2026-23455?
CVE-2026-23455 has a CVSS v4.0 base score of 9.1 (CNA self-assessment; NVD's own analysis pending).
How do I remediate CVE-2026-23455?
Patch to the fixed version published by the affected vendor. Where vendor advisories exist for CVE-2026-23455, 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

See which npm, PyPI, Go, and Maven packages are affected by CVE-2026-23455

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