CVE-2025-39737 Cert Portal CVE debrief

Who should care

Administrators and operators who rely on the Siemens advisory scope in the source corpus (SIMATIC CN 4100 versions before 5.0), plus Linux kernel maintainers and test/debug environments that enable kmemleak and watchdog monitoring.

Technical summary

The reported condition occurs in mm/kmemleak when kmemleak is disabled after it cannot allocate more kmemleak objects. Cleanup then iterates through many existing objects in __kmemleak_do_cleanup(), deleting them individually via a workqueue. On a debug kernel with a large kmemleak object pool, the repeated per-object work and locking can run long enough to cause a soft lockup warning. The supplied description says the fix is to add periodic cond_resched() calls during iteration so the kernel can yield and avoid the lockup.

Defensive priority

Medium. The impact is availability-only and appears limited to systems that hit the kmemleak-disabled cleanup path, but the supplied advisory still assigns CVSS 5.5 and recommends remediation.

Recommended defensive actions

• Apply the vendor remediation in the source corpus: update to V5.0 or later for the affected Siemens product scope.
• Treat the issue as an availability risk in debug, test, or maintenance environments where kmemleak is enabled.
• Watch for watchdog soft lockup messages and unusual delays in kmemleak cleanup on affected systems.
• Review whether kmemleak-enabled debug configurations are present in environments that should not run them.
• Use the Siemens and CISA advisory links in the source corpus to confirm the exact product scope before scheduling remediation.

Evidence notes

The source corpus contains a Linux-kernel-style fix description for kmemleak cleanup, while the advisory metadata maps the CVE to Siemens SIMATIC CN 4100 vers:intdot/<5.0. That product association is explicitly marked low confidence / needs review in the provided data, so the product mapping should be validated against the linked Siemens and CISA advisories. The corpus also states CVSS v3.1 5.5 (AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H).

Official resources