CVE-2026-74704 net/sched: sch_cake: drop WARN_ON(1) for malformed packets in ACK filter
A malformed packet can trigger a kernel warning that causes a system panic if panic_on_warn is enabled, leading to denial of service.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Over the internet
- Victim action needed
- Not needed
- Fix
- Available
What is CVE-2026-74704?
CVE-2026-74704 is a high-severity denial of service vulnerability in Linux, published on 22 Aug 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.
Official description
In the Linux kernel, the following vulnerability has been resolved:
net/sched: sch_cake: drop WARN_ON(1) for malformed packets in ACK filter
The sch_cake ACK filter parses packets to find the TCP header and filter duplicated ACKs if the flow is backlogged. The parsing code contains a WARN_ON(1) which can be triggered by a malformed IP header in certain cases. Depending on the system configuration, this leads either to either spamming dmesg with warnings, or a panic if panic_on_warn is set.
The code already correctly skips the offending packet in the branch that triggers the warning, so the WARN_ON itself doesn't really serve any purpose. So just drop it altogether to avoid the inconvenient side effects.
Which versions are affected by CVE-2026-74704?
How do I fix CVE-2026-74704?
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-2026-74704 being exploited?
There is no known exploitation of CVE-2026-74704 in the wild and no public exploit code.
Sources
Also known as AZL-97050, BELL-CVE-2026-74704, DEBIAN-CVE-2026-74704, GHSA-5x69-69gj-gg3f, UBUNTU-CVE-2026-74704.