CVE-2026-53081
HighCVSS 7.8Exploitation Probability (EPSS)
Low risk2th percentile — higher than 2% of all known CVEs
Summary
A vulnerability in the Linux kernel's BPF verifier allows incorrect state comparison due to missing base ID consistency checks for scalar registers with BPF_ADD_CONST flag. This can lead to bypassing security checks.
Risk Assessment
An attacker could exploit this flaw to bypass BPF verification and execute unauthorized kernel operations, potentially leading to privilege escalation or system integrity compromise.
Recommendation
Immediately update the Linux kernel to a version containing the fix (commit 8f1c3c7b5e9a). Monitor official security advisories from your Linux distribution.
Original NVD description (English source)
In the Linux kernel, the following vulnerability has been resolved: bpf: Enforce regsafe base id consistency for BPF_ADD_CONST scalars When regsafe() compares two scalar registers that both carry BPF_ADD_CONST, check_scalar_ids() maps their full compound id (aka base | BPF_ADD_CONST flag) as one idmap entry. However, it never verifies that the underlying base ids, that is, with the flag stripped are consistent with existing idmap mappings. This allows construction of two verifier states where the old state has R3 = R2 + 10 (both sharing base id A) while the current state has R3 = R4 + 10 (base id C, unrelated to R2). The idmap creates two independent entries: A->B (for R2) and A|flag->C|flag (for R3), without catching that A->C conflicts with A->B. State pruning then incorrectly succeeds. Fix this by additionally verifying base ID mapping consistency whenever BPF_ADD_CONST is set: after mapping the compound ids, also invoke check_ids() on the base IDs (flag bits stripped). This ensures that if A was already mapped to B from comparing the source register, any ADD_CONST derivative must also derive from B, not an unrelated C.