CVE-2025-39726: Linux kernel · s390/ism: fix concurrency management in ism_cmd()
Affects Linux kernelSource GCVE Database
Not known to be exploited · CVSS 9.8 Critical · fixed in 6.8.0-1046.49~22.04.1 : patch Linux kernel as a priority.
Data as of 26 Oct 2026, 17:16 UTC
- EPSS
- 0.2% chance of exploitation in 30 days – higher than 15% of CVEsExploit Prediction Scoring System: the likelihood attackers will use this flaw soon.
- Patch
- Available – fixed in 6.8.0-1046.49~22.04.1, 6.8.0-1051.57~22.04.1, 6.8.0-1046.53~22.04.1 +32
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 5 Sep 2025
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 25.10linux-azure-fdepkg:deb/ubuntu/linux-azure-fde?arch=source&distro=questingOther threats | Affected
| Fixed in– |
Ubuntu 24.04 LTSlinuxpkg:deb/ubuntu/linux?arch=source&distro=nobleOther threats | Affected
| Fixed in
|
Ubuntu 24.04 LTSlinux-awspkg:deb/ubuntu/linux-aws?arch=source&distro=nobleOther threats | Affected
| Fixed in
|
Ubuntu 24.04 LTSlinux-aws-6.14pkg:deb/ubuntu/linux-aws-6.14?arch=source&distro=nobleOther threats | Affected
| Fixed in
|
Ubuntu 24.04 LTSlinux-azurepkg:deb/ubuntu/linux-azure?arch=source&distro=nobleOther threats | Affected
| Fixed in
|
Ubuntu 24.04 LTSlinux-azure-6.11pkg:deb/ubuntu/linux-azure-6.11?arch=source&distro=nobleOther 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 and should be applied to affected Linux kernel versions to correct the concurrency management in the s390/ism driver. The vendor advisory from Ubuntu confirms this fix. Systems running affected versions should upgrade to patched kernel releases as soon as possible to prevent ISM device errors and connection failures.
Description
A concurrency management flaw in the Linux kernel's s390/ism driver was fixed to prevent command corruption and device error states. The s390x ISM device requires only one request-response sequence per function at a time, but the driver previously did not enforce this, leading to potential command overwrites and PCI errors. This could cause ISM functions to enter error states, breaking connections and disabling the device. The issue was addressed by adding proper synchronization in the ism_cmd() function. The vulnerability affects specific Linux kernel versions and has a high CVSS score of 9.8.
References
- ubuntu.com/security/CVE-2025-39726 (opens in a new tab)
- cve.org/CVERecord?id=CVE-2025-39726 (opens in a new tab)
- git.kernel.org/linus/897e8601b9cff1d054cdd53047f568b0e1995726 (opens in a new tab)
- git.kernel.org/stable/c/1194ad0d44d66b273a02a3a22882dc863a68d764 (opens in a new tab)
- git.kernel.org/stable/c/897e8601b9cff1d054cdd53047f568b0e1995726 (opens in a new tab)
- git.kernel.org/stable/c/faf44487dfc80817f178dc8de7a0b73f960d019b (opens in a new tab)
- git.kernel.org/stable/c/fafaa4982bedb5532f5952000f714a3e63023f40 (opens in a new tab)
- ubuntu.com/security/notices/USN-7879-1 (opens in a new tab)
- ubuntu.com/security/notices/USN-7879-2 (opens in a new tab)
- ubuntu.com/security/notices/USN-7880-1 (opens in a new tab)
- ubuntu.com/security/notices/USN-7879-3 (opens in a new tab)
- ubuntu.com/security/notices/USN-7879-4 (opens in a new tab)
- ubuntu.com/security/notices/USN-7934-1 (opens in a new tab)
- ubuntu.com/security/notices/USN-8028-1 (opens in a new tab)
- ubuntu.com/security/notices/USN-8028-2 (opens in a new tab)
- ubuntu.com/security/notices/USN-8031-1 (opens in a new tab)
- ubuntu.com/security/notices/USN-8028-3 (opens in a new tab)
- ubuntu.com/security/notices/USN-8028-4 (opens in a new tab)
- ubuntu.com/security/notices/USN-8028-5 (opens in a new tab)
- ubuntu.com/security/notices/USN-8031-2 (opens in a new tab)