Bug 2457626 (CVE-2026-31413) - CVE-2026-31413 kernel: bpf: Fix unsound scalar forking in maybe_fork_scalars() for BPF_OR
Summary: CVE-2026-31413 kernel: bpf: Fix unsound scalar forking in maybe_fork_scalars(...
Keywords:
Status: NEW
Alias: CVE-2026-31413
Product: Security Response
Classification: Other
Component: vulnerability
Version: unspecified
Hardware: All
OS: Linux
unspecified
unspecified
Target Milestone: ---
Assignee: Product Security DevOps Team
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Depends On:
Blocks:
TreeView+ depends on / blocked
 
Reported: 2026-04-12 07:01 UTC by OSIDB Bzimport
Modified: 2026-04-13 09:09 UTC (History)
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Description OSIDB Bzimport 2026-04-12 07:01:17 UTC
In the Linux kernel, the following vulnerability has been resolved:

bpf: Fix unsound scalar forking in maybe_fork_scalars() for BPF_OR

maybe_fork_scalars() is called for both BPF_AND and BPF_OR when the
source operand is a constant.  When dst has signed range [-1, 0], it
forks the verifier state: the pushed path gets dst = 0, the current
path gets dst = -1.

For BPF_AND this is correct: 0 & K == 0.
For BPF_OR this is wrong:    0 | K == K, not 0.

The pushed path therefore tracks dst as 0 when the runtime value is K,
producing an exploitable verifier/runtime divergence that allows
out-of-bounds map access.

Fix this by passing env->insn_idx (instead of env->insn_idx + 1) to
push_stack(), so the pushed path re-executes the ALU instruction with
dst = 0 and naturally computes the correct result for any opcode.


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