Bug 2461760 (CVE-2026-31675)

Summary: CVE-2026-31675 kernel: net/sched: sch_netem: fix out-of-bounds access in packet corruption
Product: [Other] Security Response Reporter: OSIDB Bzimport <bzimport>
Component: vulnerabilityAssignee: Product Security DevOps Team <prodsec-dev>
Status: NEW --- QA Contact:
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Priority: medium    
Version: unspecifiedCC: rhel-process-autobot, watson-tool-maintainers
Target Milestone: ---Keywords: Security
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Hardware: All   
OS: Linux   
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A flaw was found in the Linux kernel's netem (network emulator) module. When processing certain non-linear network packets, specifically those sent via an AF_PACKET TX_RING over an IPIP tunnel, a calculation error can occur. This error leads to an out-of-bounds memory access, which could result in system instability or a denial of service.
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Description OSIDB Bzimport 2026-04-25 09:01:44 UTC 
In the Linux kernel, the following vulnerability has been resolved:

net/sched: sch_netem: fix out-of-bounds access in packet corruption

In netem_enqueue(), the packet corruption logic uses
get_random_u32_below(skb_headlen(skb)) to select an index for
modifying skb->data. When an AF_PACKET TX_RING sends fully non-linear
packets over an IPIP tunnel, skb_headlen(skb) evaluates to 0.

Passing 0 to get_random_u32_below() takes the variable-ceil slow path
which returns an unconstrained 32-bit random integer. Using this
unconstrained value as an offset into skb->data results in an
out-of-bounds memory access.

Fix this by verifying skb_headlen(skb) is non-zero before attempting
to corrupt the linear data area. Fully non-linear packets will silently
bypass the corruption logic.
Comment 1 Alexander B 2026-04-27 10:47:15 UTC 
Upstream advisory:
https://lore.kernel.org/linux-cve-announce/2026042543-CVE-2026-31675-e5da@gregkh/T