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
70%
KEV
Not listed

Published

April 3, 2026

Last Modified

September 8, 2026

Advisory Details (10)

Auto-updated Sep 15, 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) @ questing2026-09-08ubuntu
ubuntulinux-tools-raspi-6.8 (6.8.0-1060.64) @ noble2026-09-08ubuntu
ubuntulinux-tools-fips-6.8 (6.8.0-134.134+fips1) @ noble2026-09-08ubuntu
ubuntulinux-tools-raspi-nolpae (5.15.0.1105.103) @ jammy2026-09-08ubuntu
ubuntulinux-virtual-hwe-16.04-edge (4.15.0.253.237) @ bionic2026-09-08ubuntu
ubuntulinux-tools-azure-fde-lts-24.04 (6.8.0-1062.69) @ noble2026-09-08ubuntu
ubuntulinux-tools-aws-lts-18.04 (4.15.0.1194.192) @ bionic2026-09-08ubuntu
ubuntulinux-virtual-hwe-24.04 (6.17.0-40.40~24.04.1) @ noble2026-09-08ubuntu
ubuntulinux-tools-raspi-6.17 (6.17.0-1021.21) @ questing2026-09-08ubuntu
ubuntulinux-tools-intel-iotg-edge (5.15.0.1106.112~20.04.1) @ focal2026-09-08ubuntu
ubuntulinux-tools-fips (4.4.0.1126.128) @ xenial2026-09-08ubuntu
ubuntulinux-tools-azure-6.17 (6.17.0-1021.21~24.04.1) @ noble2026-09-08ubuntu
ubuntulinux-tools-azure-fde-6.17 (6.17.0-1018.18~24.04.1) @ noble2026-09-08ubuntu
ubuntulinux-tools-azure-edge (6.8.0-1063.71~22.04.1) @ jammy2026-09-08ubuntu
ubuntulinux-tools-azure-fde-6.8 (6.8.0-1062.69~22.04.1) @ jammy2026-09-08ubuntu
ubuntulinux-tools-azure-fips-5.15 (5.15.0.1116.101) @ jammy2026-09-08ubuntu
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-0:4.18.0-305.197.1.el8_42026-07-06redhat
redhatkernel-0:3.10.0-1160.154.1.el72026-07-06redhat
redhatkernel-0:4.18.0-477.150.1.el8_82026-07-06redhat
redhatkernel-0:4.18.0-372.198.1.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-rt-0:4.18.0-553.126.1.rt7.467.el8_102026-05-28redhat
redhatkernel-0:6.12.0-211.18.1.el10_22026-05-28redhat
redhatkernel-0:5.14.0-687.12.1.el9_82026-05-28redhat
redhatkernel-0:4.18.0-553.126.1.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 (122 versions)6.19.10-1—

Weakness Classification(1)

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

Additional Vendor Advisories

(11)

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 / 28× 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 304 total refreshes for this CVE.

  1. 2026-09-18 19:27 UTCEPSS rescore
  2. 2026-09-16 14:07 UTCEPSS rescore
  3. 2026-09-16 05:15 UTCEPSS rescore
  4. 2026-09-13 16:47 UTCEPSS rescore
  5. 2026-09-12 15:01 UTCEPSS rescore
  6. 2026-09-11 14:52 UTCEPSS rescore
  7. 2026-09-10 09:34 UTCEPSS rescore
  8. 2026-09-08 22:00 UTCEPSS rescore
  9. 2026-09-08 09:14 UTCEG score recompute
  10. 2026-09-08 09:14 UTCVendor advisory
  11. 2026-09-08 09:13 UTCGHSA enrichment
  12. 2026-09-07 16:01 UTCEPSS rescore
  13. 2026-09-06 13:47 UTCEPSS rescore
  14. 2026-09-06 13:47 UTCEPSS rescore
  15. 2026-09-04 05:06 UTCEPSS rescore
  16. 2026-09-02 14:11 UTCEPSS rescore
  17. 2026-09-02 11:14 UTCOSV refresh
  18. 2026-09-01 13:53 UTCEPSS rescore
  19. 2026-09-01 04:39 UTCEPSS rescore
  20. 2026-08-30 19:17 UTCEPSS rescore
  21. 2026-08-30 01:22 UTCEPSS rescore
  22. 2026-08-28 21:41 UTCEPSS rescore
  23. 2026-08-27 14:25 UTCEPSS rescore
  24. 2026-08-26 14:46 UTCEPSS rescore
  25. 2026-08-25 13:48 UTCEPSS rescore
Show 75 more
  1. 2026-08-23 00:19 UTCEPSS rescore
  2. 2026-08-21 23:49 UTCEPSS rescore
  3. 2026-08-20 22:55 UTCEPSS rescore
  4. 2026-08-19 17:03 UTCEPSS rescore
  5. 2026-08-18 13:48 UTCEPSS rescore
  6. 2026-08-17 13:47 UTCEPSS rescore
  7. 2026-08-16 14:56 UTCEPSS rescore
  8. 2026-08-16 09:17 UTCEG score recompute
  9. 2026-08-16 09:17 UTCVendor advisory
  10. 2026-08-16 09:17 UTCGHSA enrichment
  11. 2026-08-16 02:14 UTCEPSS rescore
  12. 2026-08-15 01:30 UTCEPSS rescore
  13. 2026-08-14 22:56 UTCVendor advisory
  14. 2026-08-14 22:56 UTCGHSA enrichment
  15. 2026-08-14 18:52 UTCVendor advisory
  16. 2026-08-14 18:52 UTCGHSA enrichment
  17. 2026-08-14 13:51 UTCVendor advisory
  18. 2026-08-14 13:51 UTCGHSA enrichment
  19. 2026-08-14 09:47 UTCVendor advisory
  20. 2026-08-14 09:47 UTCGHSA enrichment
  21. 2026-08-14 05:43 UTCEG score recompute
  22. 2026-08-14 05:43 UTCVendor advisory
  23. 2026-08-14 05:43 UTCGHSA enrichment
  24. 2026-08-13 22:00 UTCEPSS rescore
  25. 2026-08-13 09:56 UTCVendor advisory
  26. 2026-08-13 09:56 UTCGHSA enrichment
  27. 2026-08-13 04:06 UTCVendor advisory
  28. 2026-08-13 04:06 UTCGHSA enrichment
  29. 2026-08-13 00:02 UTCVendor advisory
  30. 2026-08-13 00:02 UTCGHSA enrichment
  31. 2026-08-12 19:58 UTCEG score recompute
  32. 2026-08-12 19:58 UTCVendor advisory
  33. 2026-08-12 19:58 UTCGHSA enrichment
  34. 2026-08-12 13:50 UTCEPSS rescore
  35. 2026-08-12 00:40 UTCVendor advisory
  36. 2026-08-12 00:39 UTCGHSA enrichment
  37. 2026-08-11 20:17 UTCEG score recompute
  38. 2026-08-11 20:17 UTCVendor advisory
  39. 2026-08-11 20:17 UTCGHSA enrichment
  40. 2026-08-11 13:42 UTCEPSS rescore
  41. 2026-08-11 07:30 UTCVendor advisory
  42. 2026-08-11 07:30 UTCGHSA enrichment
  43. 2026-08-11 03:26 UTCEG score recompute
  44. 2026-08-11 03:26 UTCVendor advisory
  45. 2026-08-11 03:26 UTCGHSA enrichment
  46. 2026-08-11 00:00 UTCEPSS rescore
  47. 2026-08-10 09:18 UTCVendor advisory
  48. 2026-08-10 09:18 UTCGHSA enrichment
  49. 2026-08-10 05:14 UTCVendor advisory
  50. 2026-08-10 05:14 UTCGHSA enrichment
  51. 2026-08-10 01:11 UTCVendor advisory
  52. 2026-08-10 01:11 UTCGHSA enrichment
  53. 2026-08-09 21:06 UTCVendor advisory
  54. 2026-08-09 21:06 UTCGHSA enrichment
  55. 2026-08-09 17:03 UTCEG score recompute
  56. 2026-08-09 17:03 UTCVendor advisory
  57. 2026-08-09 17:03 UTCGHSA enrichment
  58. 2026-08-09 13:46 UTCEPSS rescore
  59. 2026-08-09 12:59 UTCVendor advisory
  60. 2026-08-09 12:59 UTCGHSA enrichment
  61. 2026-08-09 05:14 UTCEG score recompute
  62. 2026-08-09 05:14 UTCVendor advisory
  63. 2026-08-09 05:14 UTCGHSA enrichment
  64. 2026-08-08 16:37 UTCEPSS rescore
  65. 2026-08-08 11:46 UTCVendor advisory
  66. 2026-08-08 11:46 UTCGHSA enrichment
  67. 2026-08-08 07:36 UTCVendor advisory
  68. 2026-08-08 07:36 UTCGHSA enrichment
  69. 2026-08-08 03:32 UTCVendor advisory
  70. 2026-08-08 03:32 UTCGHSA enrichment
  71. 2026-08-07 23:28 UTCVendor advisory
  72. 2026-08-07 23:28 UTCGHSA enrichment
  73. 2026-08-07 19:24 UTCEG score recompute
  74. 2026-08-07 19:24 UTCVendor advisory
  75. 2026-08-07 19:24 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 September 8, 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 30.0% 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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