CVE-2026-23398: Linux kernel · icmp: fix NULL pointer dereference in icmp_tag_validation()
Affects Linux kernelSource GCVE Database
Not known to be exploited · CVSS 5.5 Medium · patch available : update Linux kernel when convenient.
Data as of 26 Oct 2026, 12:55 UTC
- EPSS
- 0.1% chance of exploitation in 30 days – higher than 2% of CVEsExploit Prediction Scoring System: the likelihood attackers will use this flaw soon.
- Patch
- Available
CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:HExploitation evidence
Disclosed: evidence found.
CVE published 26 Mar 2026
Detectable: no evidence on record.
No public nuclei template indexed
Weaponised: no evidence on record.
No public exploit code indexed in Metasploit or Exploit-DB
Exploited in the wildExploited: no evidence on record.
Not in CISA KEV and no source reports exploitation
Observed by OffSeq MirageSeen by Mirage: no evidence on record.
No attack traffic recorded by OffSeq Mirage sensors
A missing step is not evidence of safety. Sources: cve.org (opens in a new tab), the Metasploit, Exploit-DB and nuclei-templates index as of 26 Oct 2026.
What to do
Affected software
| Product | Affected | Fixed in |
|---|---|---|
Ubuntu 25.10linuxpkg:deb/ubuntu/linux@6.17.0-40.40?arch=source&distro=questingOther threats | Affected
| Fixed in– |
Ubuntu 25.10linux-awspkg:deb/ubuntu/linux-aws@6.17.0-1019.19?arch=source&distro=questingOther threats | Affected
| Fixed in– |
Ubuntu 25.10linux-azurepkg:deb/ubuntu/linux-azure@6.17.0-1020.20?arch=source&distro=questingOther threats | Affected
| Fixed in– |
Ubuntu 25.10linux-azure-fdepkg:deb/ubuntu/linux-azure-fde@6.17.0-1017.17?arch=source&distro=questingOther threats | Affected
| Fixed in– |
Ubuntu 25.10linux-gcppkg:deb/ubuntu/linux-gcp@6.17.0-1020.22?arch=source&distro=questingOther threats | Affected
| Fixed in– |
Ubuntu 25.10linux-oraclepkg:deb/ubuntu/linux-oracle@6.17.0-1018.18?arch=source&distro=questingOther threats | Affected
| Fixed in– |
Check your own hosts for these packages with threat-finder (opens in a new tab), our free open-source scanner.
AI-suggested
An official patch is available and should be applied to affected linux-aws kernel versions. The patch adds a NULL pointer check in icmp_tag_validation() to prevent kernel panic. Users should update to patched kernel versions as per vendor advisories. No additional mitigations are indicated.
Description
A NULL pointer dereference vulnerability in the Linux kernel's icmp_tag_validation() function was fixed. The function unconditionally dereferenced a pointer without checking for NULL, which could cause a kernel panic when handling certain ICMP Fragmentation Needed errors with unregistered protocol numbers. This issue affects specific linux-aws kernel versions and results in a denial of service via kernel panic. A patch is available to add the necessary NULL check and prevent the crash.
References
- ubuntu.com/security/CVE-2026-23398 (opens in a new tab)
- cve.org/CVERecord?id=CVE-2026-23398 (opens in a new tab)
- git.kernel.org/linus/614aefe56af8e13331e50220c936fc0689cf5675 (opens in a new tab)
- git.kernel.org/stable/c/1e4e2f5e48cec0cccaea9815fb9486c084ba41e2 (opens in a new tab)
- git.kernel.org/stable/c/1f9f2c6d4b2a613b7756fc5679c5116ba2ca0161 (opens in a new tab)
- git.kernel.org/stable/c/614aefe56af8e13331e50220c936fc0689cf5675 (opens in a new tab)
- git.kernel.org/stable/c/9647e99d2a617c355d2b378be0ff6d0e848fd579 (opens in a new tab)
- git.kernel.org/stable/c/b61529c357f1ee4d64836eb142a542d2e7ad67ce (opens in a new tab)
- git.kernel.org/stable/c/d938dd5a0ad780c891ea3bc94cae7405f11e618a (opens in a new tab)
- ubuntu.com/security/notices/USN-8567-1 (opens in a new tab)
- ubuntu.com/security/notices/USN-8574-1 (opens in a new tab)
- ubuntu.com/security/notices/USN-8575-1 (opens in a new tab)
- ubuntu.com/security/notices/USN-8576-1 (opens in a new tab)
- ubuntu.com/security/notices/USN-8574-2 (opens in a new tab)
- ubuntu.com/security/notices/USN-8595-1 (opens in a new tab)
- ubuntu.com/security/notices/USN-8596-1 (opens in a new tab)
- ubuntu.com/security/notices/USN-8575-2 (opens in a new tab)
- ubuntu.com/security/notices/USN-8576-2 (opens in a new tab)
- ubuntu.com/security/notices/USN-8597-1 (opens in a new tab)
- ubuntu.com/security/notices/USN-8595-2 (opens in a new tab)