CVE-2026-80733: Linux kernel · net: remove WARN_ON_ONCE() from sk_mc_loop()
Affects Linux kernelSource GCVE Database
Not known to be exploited · fixed in 5.15.0-1117.124~20.04.1 : update Linux kernel when convenient.
Data as of 26 Oct 2026, 17:16 UTC
Rated by Threat Radar · CVSS not yet scored by NVD
- EPSS
- 0.1% chance of exploitation in 30 days – higher than 7% of CVEsExploit Prediction Scoring System: the likelihood attackers will use this flaw soon.
- Patch
- Available – fixed in 5.15.0-1117.124~20.04.1, 5.15.0-1123.132~20.04.1, 5.15.0-1122.131~20.04.1 +27
Exploitation evidence
Disclosed: evidence found.
CVE published 3 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
Upgrade to a fixed release listed under Affected software.
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 patch is available that removes the WARN_ON_ONCE() call from sk_mc_loop(). Users should apply the official Linux kernel updates that address this issue. The vendor advisory confirms that this vulnerability has been fixed.
Description
A vulnerability in the Linux kernel's network subsystem was resolved by removing a WARN_ON_ONCE() call from the sk_mc_loop() function. The issue occurs because sk_mc_loop() can be called for sockets that are neither AF_INET nor AF_INET6, such as AF_PACKET sockets used over virtual devices. In these cases, the function triggers a warning unnecessarily. This does not affect multicast loopback behavior for non-INET sockets, which should default to true without warnings.
References
- ubuntu.com/security/CVE-2026-80733 (opens in a new tab)
- cve.org/CVERecord?id=CVE-2026-80733 (opens in a new tab)
- git.kernel.org/linus/b8a39a09ae4eaae04309e1e38ed6a1101d967496 (opens in a new tab)
- git.kernel.org/stable/c/0d75f2c1d0764efa756ad9c1e078d8c09ea8fc1f (opens in a new tab)
- git.kernel.org/stable/c/97133c4d42654578fab95abe47359ebe784dde18 (opens in a new tab)
- git.kernel.org/stable/c/ad7dbb1d14b1b4406eca8ef9478e8de312ba0cfe (opens in a new tab)
- git.kernel.org/stable/c/ad7fa2f411cb30f63d6725f111be134064cdb718 (opens in a new tab)
- git.kernel.org/stable/c/b8a39a09ae4eaae04309e1e38ed6a1101d967496 (opens in a new tab)
- git.kernel.org/stable/c/c8f256dc849205ccb2bd78bd99a3497b972b44e0 (opens in a new tab)
- git.kernel.org/stable/c/d2adc4e80b29e58b5162ae09f0f657a215806c8c (opens in a new tab)
- git.kernel.org/stable/c/f625c742b33dc137c209dd13d1c5f12b1c18d71c (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-8875-2 (opens in a new tab)