Bug 2516305 (CVE-2026-72423)

Summary: CVE-2026-72423 kernel: bpf: Guard conntrack opts error writes
Product: [Other] Security Response Reporter: OSIDB Bzimport <bzimport>
Component: vulnerabilityAssignee: Product Security DevOps Team <prodsec-dev>
Status: NEW --- QA Contact:
Severity: medium Docs Contact:
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. The BPF (Berkeley Packet Filter) subsystem's conntrack (connection tracking) functionality contains an out-of-bounds write vulnerability. This occurs because the system does not properly validate the size of an options structure when reporting errors in conntrack lookup and allocation kernel functions (kfuncs). An attacker could potentially exploit this by providing an invalid size, leading to memory corruption.
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Description OSIDB Bzimport 2026-08-15 06:05:31 UTC 
In the Linux kernel, the following vulnerability has been resolved:

bpf: Guard conntrack opts error writes

The conntrack lookup and allocation kfuncs take an opts pointer
together with an opts__sz argument. The verifier checks only the memory
range described by opts__sz, but the wrappers unconditionally write
opts->error whenever the internal lookup or allocation helper returns an
error.

For an invalid size smaller than the end of opts->error, that write can
land outside the verifier-checked range. Keep returning NULL for invalid
arguments, but only report the error through opts->error when the
supplied size includes the field.

This preserves error reporting for the supported 12-byte and 16-byte
layouts, and for other invalid sizes that still include opts->error.
Comment 1 gkamathe 2026-08-18 06:12:40 UTC 
Upstream advisory:
https://lore.kernel.org/linux-cve-announce/2026081526-CVE-2026-72423-9fac@gregkh/T