CVE-2026-43376: Linux kernel · ksmbd: fix use-after-free by using call_rcu() for oplock_info
Affects Linux kernelSource GCVE Database
Not known to be exploited · CVSS 9.8 Critical · fixed in 6.17.0-1019.19~24.04.1 : patch Linux kernel as a priority.
Data as of 26 Oct 2026, 14:05 UTC
- EPSS
- 0.4% chance of exploitation in 30 days – higher than 38% of CVEsExploit Prediction Scoring System: the likelihood attackers will use this flaw soon.
- Patch
- Available – fixed in 6.17.0-1019.19~24.04.1, 6.17.0-1020.22~24.04.1, 6.17.0-40.40~24.04.1 +11
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 8 May 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 LTSlinux-azure-fdepkg:deb/ubuntu/linux-azure-fde@7.0.0-1008.8?arch=source&distro=resoluteOther threats | 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
|
Check your own hosts for these packages with threat-finder (opens in a new tab), our free open-source scanner.
Description
In the Linux kernel, the following vulnerability has been resolved: ksmbd: fix use-after-free by using call_rcu() for oplock_info ksmbd currently frees oplock_info immediately using kfree(), even though it is accessed under RCU read-side critical sections in places like opinfo_get() and proc_show_files(). Since there is no RCU grace period delay between nullifying the pointer and freeing the memory, a reader can still access oplock_info structure after it has been freed. This can leads to a use-after-free especially in opinfo_get() where atomic_inc_not_zero() is called on already freed memory. Fix this by switching to deferred freeing using call_rcu().
References
- ubuntu.com/security/CVE-2026-43376 (opens in a new tab)
- cve.org/CVERecord?id=CVE-2026-43376 (opens in a new tab)
- git.kernel.org/linus/1dfd062caa165ec9d7ee0823087930f3ab8a6294 (opens in a new tab)
- git.kernel.org/stable/c/08aa9f3c8cf4d0bee44df540dfe34e8d64069f2c (opens in a new tab)
- git.kernel.org/stable/c/1d6abf145615dbfe267ce3b0a271f95e3780e18e (opens in a new tab)
- git.kernel.org/stable/c/1dfd062caa165ec9d7ee0823087930f3ab8a6294 (opens in a new tab)
- git.kernel.org/stable/c/302fef75512b2c8329a3f5efab1ae7ba2562387a (opens in a new tab)
- git.kernel.org/stable/c/ce8507ee82c888126d8e7565e27c016308d24cde (opens in a new tab)
- ubuntu.com/security/notices/USN-8490-1 (opens in a new tab)
- ubuntu.com/security/notices/USN-8491-1 (opens in a new tab)
- ubuntu.com/security/notices/USN-8508-1 (opens in a new tab)
- ubuntu.com/security/notices/USN-8490-2 (opens in a new tab)
- ubuntu.com/security/notices/USN-8545-1 (opens in a new tab)
- ubuntu.com/security/notices/USN-8546-1 (opens in a new tab)
- ubuntu.com/security/notices/USN-8604-1 (opens in a new tab)
- ubuntu.com/security/notices/USN-8605-1 (opens in a new tab)