CVE-2026-23436
MediumCVSS 5.5Exploitation Probability (EPSS)
Low risk2th percentile - higher than 2% of all known CVEs
Summary
In the Linux kernel's network shaper mechanism, there is a race condition between Netlink operations and network device unregistration. This can lead to a shaper hierarchy leak if the hierarchy is created after a flush has already run.
Risk Assessment
Risk of kernel memory leak and potential resource exhaustion by an attacker who can deliberately trigger this race.
Recommendation
Apply a patch that moves the instance lock to the Netlink pre-phase, eliminating the race window.
Original NVD description (English source)
In the Linux kernel, the following vulnerability has been resolved: net: shaper: protect from late creation of hierarchy We look up a netdev during prep of Netlink ops (pre- callbacks) and take a ref to it. Then later in the body of the callback we take its lock or RCU which are the actual protections. The netdev may get unregistered in between the time we take the ref and the time we lock it. We may allocate the hierarchy after flush has already run, which would lead to a leak. Take the instance lock in pre- already, this saves us from the race and removes the need for dedicated lock/unlock callbacks completely. After all, if there's any chance of write happening concurrently with the flush - we're back to leaking the hierarchy. We may take the lock for devices which don't support shapers but we're only dealing with SET operations here, not taking the lock would be optimizing for an error case.