Linux Kernel Sch_Cake ACK Filter WARN_ON Causing PANIC (CVE-2026-74704)
CVE-2026-74704 Published on August 22, 2026
net/sched: sch_cake: drop WARN_ON(1) for malformed packets in ACK filter
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.
Products Associated with CVE-2026-74704
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Affected Versions
Linux:- Version 8b7138814f29933898ecd31dfc83e35a30ee69f5 and below c1693b7844a6c06d31a565e5a494948034dfd235 is affected.
- Version 8b7138814f29933898ecd31dfc83e35a30ee69f5 and below a4b52612004a5639c4bfc30ba93ba414b8326e2a is affected.
- Version 8b7138814f29933898ecd31dfc83e35a30ee69f5 and below ae1b2f8e21a41e7c7e75511bea0c4ccc59ec1bd3 is affected.
- Version 8b7138814f29933898ecd31dfc83e35a30ee69f5 and below 0c4882bff34558d8d53fb04c3e96da5c327c7dc8 is affected.
- Version 8b7138814f29933898ecd31dfc83e35a30ee69f5 and below 2504a76e5c0694e14e15562730e1339f2d9f9458 is affected.
- Version 8b7138814f29933898ecd31dfc83e35a30ee69f5 and below cd2f1d9fe8a507c2dc86ad326fe221f121c47734 is affected.
- Version 8b7138814f29933898ecd31dfc83e35a30ee69f5 and below a1ae353d8355407c1bea971d1c1af5e7f242bb7d is affected.
- Version 8b7138814f29933898ecd31dfc83e35a30ee69f5 and below 2a33516f9ef59ad11844d4fc152f889449b5daf3 is affected.
- Version 4.19 is affected.
- Before 4.19 is unaffected.
- Version 5.10.265, <= 5.10.* is unaffected.
- Version 5.15.216, <= 5.15.* is unaffected.
- Version 6.1.183, <= 6.1.* is unaffected.
- Version 6.6.152, <= 6.6.* is unaffected.
- Version 6.12.104, <= 6.12.* is unaffected.
- Version 6.18.45, <= 6.18.* is unaffected.
- Version 7.1.9, <= 7.1.* is unaffected.
- Version 7.2, <= * is unaffected.