CVE-2026-89550: Linux kernel · SUNRPC: svcauth_gss: enforce krb5 token minimum length
Affects Linux kernelSource GCVE Database
Not known to be exploited · CVSS 9.8 Critical.
Data as of 26 Oct 2026, 14:05 UTC
- EPSS
- 0.4% chance of exploitation in 30 days – higher than 39% of CVEsExploit Prediction Scoring System: the likelihood attackers will use this flaw soon.
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:HExploitation evidence
Disclosed: evidence found.
CVE published 11 Sep 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 26.04 LTSlinuxpkg:deb/ubuntu/linux?arch=source&distro=resoluteOther threats | Affected
| Fixed in– |
Ubuntu 26.04 LTSlinux-awspkg:deb/ubuntu/linux-aws?arch=source&distro=resoluteOther threats | Affected
| Fixed in– |
Ubuntu 26.04 LTSlinux-azurepkg:deb/ubuntu/linux-azure?arch=source&distro=resoluteOther threats | Affected
| Fixed in– |
Ubuntu 26.04 LTSlinux-azure-fdepkg:deb/ubuntu/linux-azure-fde?arch=source&distro=resoluteOther threats | Affected
| Fixed in– |
Ubuntu 26.04 LTSlinux-gcppkg:deb/ubuntu/linux-gcp?arch=source&distro=resoluteOther threats | Affected
| Fixed in– |
Ubuntu 26.04 LTSlinux-gkepkg:deb/ubuntu/linux-gke?arch=source&distro=resoluteOther 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
A fix is available that adds a minimum-length check to the svcauth_gss_unwrap_priv() function to reject tokens that are too short before they reach the Kerberos unwrap core. Users should apply the official Linux kernel updates that include this fix. Since this is a kernel vulnerability, upgrading to a patched kernel version is the recommended remediation.
Description
A vulnerability in the Linux kernel's SUNRPC svcauth_gss component allows a specially crafted Kerberos v5 token with an insufficient length to trigger a division-by-zero error during token unwrapping. This occurs because the svcauth_gss_unwrap_priv() function only enforces an upper bound on the token length but not a minimum length, allowing tokens of length 16 bytes or less to be processed incorrectly. The issue is fixed by adding a minimum-length check to reject tokens that are too short before they reach the Kerberos unwrap core.
References
- nvd.nist.gov/vuln/detail/CVE-2026-89550 (opens in a new tab)
- git.kernel.org/stable/c/2eed1e6a976a44015c3ee78841fe336796e2b21c (opens in a new tab)
- git.kernel.org/stable/c/a919c5c88769cf8fb3ec071e6078d830bf512489 (opens in a new tab)
- git.kernel.org/stable/c/dd6afc6cab8c5d387d1ed2f069562ef7bdadd651 (opens in a new tab)
- git.kernel.org/stable/c/de942dd8c2c8358bcad04ce44271954c48924423 (opens in a new tab)
- ubuntu.com/security/CVE-2026-89550 (opens in a new tab)
- cve.org/CVERecord?id=CVE-2026-89550 (opens in a new tab)
- git.kernel.org/linus/a919c5c88769cf8fb3ec071e6078d830bf512489 (opens in a new tab)
- msrc.microsoft.com/csaf/vex/2026/msrc_cve-2026-89550.json (opens in a new tab)
- support.microsoft.com/lifecycle (opens in a new tab)
- first.org/cvss (opens in a new tab)