CVE-2026-98253: Linux kernel · RDMA/ucma: Serialize join and leave on copy_to_user failure
Affects Linux kernelSource GCVE Database
Not known to be exploited · CVSS 7.8 High.
Data as of 26 Oct 2026, 14:05 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.
CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:HExploitation evidence
Disclosed: evidence found.
CVE published 6 Oct 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 properly serializes join and leave multicast operations by holding the mutex throughout the critical sections, preventing the race condition. Users should apply the official Linux kernel updates that include this patch. Since this is not a cloud service, manual patching is required. No alternative mitigations are indicated by the vendor advisory.
Description
A vulnerability in the Linux kernel's RDMA/ucma subsystem related to multicast join and leave operations has been resolved. The issue involves improper serialization of join and leave calls on copy_to_user failure, which could lead to use-after-free conditions. This occurs when two concurrent join multicast calls with the same address cause a race condition, potentially allowing an older worker to dereference freed memory. The fix ensures the mutex is held properly during these operations to prevent this race.
References
- ubuntu.com/security/CVE-2026-98253 (opens in a new tab)
- cve.org/CVERecord?id=CVE-2026-98253 (opens in a new tab)
- git.kernel.org/linus/662ade4de9ff5eceb0820a9f8e9fac70ba6a815b (opens in a new tab)
- git.kernel.org/stable/c/01cbdb724c584d7772fd25af2e4dfdf8527ce0d5 (opens in a new tab)
- git.kernel.org/stable/c/01e29d0d78a8f66f221625720a04939eef5ec1f6 (opens in a new tab)
- git.kernel.org/stable/c/29b9ed83d8bfab5c6e11fcbf1aa836aa4ae26cb9 (opens in a new tab)
- git.kernel.org/stable/c/43c4e24bd10370fc976f6220518049ce71419399 (opens in a new tab)
- git.kernel.org/stable/c/52172e11bd074ccaded21740ffeb67123f01dd00 (opens in a new tab)
- git.kernel.org/stable/c/662ade4de9ff5eceb0820a9f8e9fac70ba6a815b (opens in a new tab)
- git.kernel.org/stable/c/83610ee5e498fa5bfcb80031d2b959baea276bf6 (opens in a new tab)
- git.kernel.org/stable/c/ae805d204cf1f15b87d1bf3529b4c649f3519420 (opens in a new tab)