CVE-2026-98049

/// Technical description

In the Linux kernel, the following vulnerability has been resolved:

bpf: zero extend the result of an arena 32-bit cmpxchg

bpf_convert_ctx_accesses() rewrites an atomic on an arena pointer from

BPF_STX | BPF_ATOMIC to BPF_STX | BPF_PROBE_ATOMIC, and it runs before

bpf_opt_subreg_zext_lo32_rnd_hi32().

That pass emits an explicit zero extension for a 32-bit cmpxchg even

when bpf_jit_needs_zext() is false. This is done because on some

architectures 32-bit cmpxchg requires explicit zero extension for the

dst register. E.g. on x86-64 'lock cmpxchg' does not change the %eax

if comparison is successful, while BPF semantics declare that each

operation on a 32-bit register zero extends it's upper half.

is_cmpxchg_insn() matches BPF_MODE == BPF_ATOMIC only, so an arena

cmpxchg misses said zero extension adjustment. This patch adjusts

is_cmpxchg_insn() to match BPF_PROBE_ATOMIC alongside BPF_ATOMIC.

/// Remediation

Check the references section for vendor advisories and patches from linux. Update linux_kernel to the latest patched version. If immediate patching is not possible, review the CVSS vector to understand the attack surface and apply compensating controls such as network segmentation or access restrictions.

/// Affected products

/// References