CVE-2026-23455: netfilter: nf_conntrack_h323: check for zero length in DecodeQ931()
Vulnerability summary
CVE-2026-23455 is a critical (CVSS 9.1) Out-of-bounds Read vulnerability in linux. EPSS estimates a 1.59% chance of exploitation in the next 30 days, higher than 75.6% of scored vulnerabilities.
Severe, CVSS 9.1 (CVE.org); no exploitation reported by the 5 checked sources; EPSS 2% (FIRST, 03-11-2026)
Source freshness unavailable
How is this decided?Advisory lineage
Upstream 0 · Downstream 50 · Related 40Timeline
- 03-04-2026PublishedVulnerability first disclosed.
- 19-10-2026Last modifiedVulnerability information updated.
Description
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 metrics
5 scores · 4 sources · 2 versions- OSV · UbuntuEcosystem advisory · calculated9.1CriticalCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:H
- OSV · DebianEcosystem advisory · calculated9.1CriticalCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:H
- NVDNIST9.1CriticalCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:H
EPSS trend
Probability
1.59%
Chance of exploitation in the next 30 days
Percentile
76%
Versus all other CVEs
30-day change
Increase +0.25 pp
From 1.34% on 04-10-2026
Known exploited
Compare KEV catalogs
CISA KEVNot in the CISA KEV catalog.
ENISA CNWNot in the ENISA CNW catalog.
CIRCLNot in the CIRCL catalog.
Public exploits
0 foundNo public exploits indexed.
Weaknesses
CWE · root causeAffected systems
Known conditions: network-reachable, no authentication, no user interaction (CVSS vector). Other conditions: not stated in public data.
Ubuntu157 products
- linux< 3.13.0-214.265 | < 4.4.0-283.317 | < 4.15.0-253.265 | < 5.4.0-233.253 | < 5.15.0-185.195 | < 6.8.0-134.134 | < 6.17.0-40.40
- linux-allwinner-5.19All versions (No fix recorded)
- linux-aws< 4.4.0-1156.162 | < 4.4.0-1194.209 | < 4.15.0-1194.207 | < 5.4.0-1161.172 | < 5.15.0-1111.118 | < 6.8.0-1060.63 | < 6.17.0-1019.19
- linux-aws-5.0All versions (No fix recorded)
- linux-aws-5.11All versions (No fix recorded)
Linux2 products
- linux≥ 5e35941d990123f155b02d5663e51a24f816b6f3, < 2121f5fbe88daff0f1fc5bc47d359426c74b86b0 | ≥ 5e35941d990123f155b02d5663e51a24f816b6f3, < 65fa92f79677858b14b9e4b7275f26639afe2710 | ≥ 5e35941d990123f155b02d5663e51a24f816b6f3, < 495e97af9e7249ee02b72bb1d0848a6efc3700f4 | ≥ 5e35941d990123f155b02d5663e51a24f816b6f3, < f5e4f4e4cdb75ec36802059a94195a31f193da60 | ≥ 5e35941d990123f155b02d5663e51a24f816b6f3, < 633e8f87dad32263f6a57dccdb873f042c062111 | ≥ 5e35941d990123f155b02d5663e51a24f816b6f3, < 9d00fe7d6d7c5b5f1065a6e042b54f2e44bd6df8 | ≥ 5e35941d990123f155b02d5663e51a24f816b6f3, < b652b05d51003ac074b912684f9ec7486231717b | ≥ 5e35941d990123f155b02d5663e51a24f816b6f3, < f173d0f4c0f689173f8cdac79991043a4a89bf66 | 2.6.17
- linux_kernel≥ 2.6.17, < 5.10.253 | ≥ 5.11, < 5.15.203 | ≥ 5.16, < 6.1.167 | ≥ 6.2, < 6.6.130 | ≥ 6.7, < 6.12.78 | ≥ 6.13, < 6.18.20 | ≥ 6.19, < 6.19.10 | 7.0:rc1 | 7.0:rc2 | 7.0:rc3 | 7.0:rc4
Debian1 product
- linux< 6.1.170-1 | < 6.12.85-1 | < 6.19.10-1
3 vendors · 160 products
