CVE-2025-39768 net/mlx5: HWS, fix complex rules rehash error flow
A flaw in the Linux kernel's mlx5 network driver causes soft lock-ups during complex rule rehash errors, leading to system denial of service.
- Exploited in the wild
- Not known
- Login needed
- Any signed-in user
- Attackable
- Local or same network only
- Victim action needed
- Not needed
- Fix
- Available
What is CVE-2025-39768?
CVE-2025-39768 is a medium-severity denial of service vulnerability in Linux kernel, published on 11 Sep 2025. It can only be exploited from the same machine or local network, with no action from the victim.
Official description
In the Linux kernel, the following vulnerability has been resolved:
net/mlx5: HWS, fix complex rules rehash error flow
Moving rules from matcher to matcher should not fail. However, if it does fail due to various reasons, the error flow should allow the kernel to continue functioning (albeit with broken steering rules) instead of going into series of soft lock-ups or some other problematic behaviour.
Similar to the simple rules, complex rules rehash logic suffers from the same problems. This patch fixes the error flow for moving complex rules: - If new rule creation fails before it was even enqeued, do not poll for completion - If TIMEOUT happened while moving the rule, no point trying to poll for completions for other rules. Something is broken, completion won't come, just abort the rehash sequence. - If some other completion with error received, don't give up. Continue handling rest of the rules to minimize the damage. - Make sure that the first error code that was received will be actually returned to the caller instead of replacing it with the generic error code.
All the aforementioned issues stem from the same bad error flow, so no point fixing them one by one and leaving partially broken code - fixing them in one patch.
Weakness: CWE-617
Which versions are affected by CVE-2025-39768?
It affects 1 product.
Products include Linux kernel.
How do I fix CVE-2025-39768?
Apply the vendor's patch.
Upgrade, then put limits on request size, rate and nesting depth so one client cannot exhaust the service. More about Denial of service.
Is CVE-2025-39768 being exploited?
There is no known exploitation of CVE-2025-39768 in the wild and no public exploit code.
Other vulnerabilities in Linux kernel
Sources
Also known as BELL-CVE-2025-39768, DEBIAN-CVE-2025-39768, GHSA-9vj3-c3f5-qhqx, UBUNTU-CVE-2025-39768.