CVE-2026-72166: Linux kernel · net/9p: fix infinite loop in p9_client_rpc on fatal signal
Affects Linux kernelSource GCVE Database
Not known to be exploited · fixed in 5.4 : update Linux kernel when convenient.
Data as of 26 Oct 2026, 14:05 UTC
Rated by Threat Radar · CVSS not yet scored by NVD
- EPSS
- 0.2% chance of exploitation in 30 days – higher than 11% of CVEsExploit Prediction Scoring System: the likelihood attackers will use this flaw soon.
- Patch
- Available – fixed in 5.4, 5.15.0-1117.124~20.04.1, 5.15.0-1123.132~20.04.1 +42
Exploitation evidence
Disclosed: evidence found.
CVE published 15 Aug 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
Upgrade to a fixed release listed under Affected software.
Affected software
| Product | Affected | Fixed in |
|---|---|---|
Debiandebian/linuxpkg:deb/debian/linuxOther threats | Affected
| Fixed in
|
Ubuntu Pro 14.04 LTSlinuxpkg:deb/ubuntu/linux?arch=source&distro=esm-infra-legacy/trustyOther threats | Affected
| Fixed in– |
Ubuntu Pro 14.04 LTSlinux-awspkg:deb/ubuntu/linux-aws?arch=source&distro=esm-infra-legacy/trustyOther threats | Affected
| Fixed in– |
Ubuntu Pro 14.04 LTSlinux-azurepkg:deb/ubuntu/linux-azure?arch=source&distro=esm-infra-legacy/trustyOther threats | Affected
| Fixed in– |
Ubuntu Pro 14.04 LTSlinux-lts-xenialpkg:deb/ubuntu/linux-lts-xenial?arch=source&distro=esm-infra-legacy/trustyOther threats | Affected
| Fixed in– |
Ubuntu Pro 16.04 LTSlinuxpkg:deb/ubuntu/linux?arch=source&distro=esm-infra-legacy/xenialOther 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 patch is available that fixes the infinite loop by checking for pending fatal signals before clearing the signal pending flag in the P9_TFLUSH retry loop. Users should apply the official Linux kernel updates that include this fix. The vendor advisory confirms the availability of this fix. No additional mitigation is required beyond applying the patch.
Description
A vulnerability in the Linux kernel's 9p network protocol client (p9_client_rpc) causes an infinite loop when handling fatal signals during a P9_TFLUSH operation over a transport with no peer. This can lead to a thread hang and stall system shutdown or coredump processes. The flaw affects kernels back to version 5.4 and some earlier versions. A fix is available that checks for pending fatal signals before retrying the operation, preventing the infinite loop.
References
- nvd.nist.gov/vuln/detail/CVE-2026-72166 (opens in a new tab)
- git.kernel.org/stable/c/378481cc60a937ef8ea4ef6e4f95f0dbc4e21414 (opens in a new tab)
- git.kernel.org/stable/c/4f621ae3a2d99b0bac50e8d66cbf7f68323c01e8 (opens in a new tab)
- git.kernel.org/stable/c/6b4f48728faa8bb514368f7eacda05565dea8696 (opens in a new tab)
- git.kernel.org/stable/c/823886a1b089b49bcd349bc8bd3417b7910cd1ac (opens in a new tab)
- git.kernel.org/stable/c/a8874c34c4a973f9922908a4b8be1d1278f01e42 (opens in a new tab)
- git.kernel.org/stable/c/dc892cbb1e4341d427b1f940ebd6abd69bf8e479 (opens in a new tab)
- git.kernel.org/stable/c/f62a1f245a71680033260a6f6d74011cc3acb3cd (opens in a new tab)
- ubuntu.com/security/CVE-2026-72166 (opens in a new tab)
- cve.org/CVERecord?id=CVE-2026-72166 (opens in a new tab)
- git.kernel.org/linus/6b4f48728faa8bb514368f7eacda05565dea8696 (opens in a new tab)
- ubuntu.com/security/notices/USN-8876-1 (opens in a new tab)
- ubuntu.com/security/notices/USN-8878-1 (opens in a new tab)
- ubuntu.com/security/notices/USN-8879-1 (opens in a new tab)
- ubuntu.com/security/notices/USN-8877-1 (opens in a new tab)
- ubuntu.com/security/notices/USN-8875-1 (opens in a new tab)
- ubuntu.com/security/notices/USN-8888-1 (opens in a new tab)
- ubuntu.com/security/notices/USN-8889-1 (opens in a new tab)
- ubuntu.com/security/notices/USN-8887-1 (opens in a new tab)
- ubuntu.com/security/notices/USN-8888-2 (opens in a new tab)
- ubuntu.com/security/notices/USN-8887-2 (opens in a new tab)