CVE-2026-53081 bpf: Enforce regsafe base id consistency for BPF_ADD_CONST scalars
A logic error in the Linux kernel BPF verifier allows incorrect state pruning, potentially enabling privilege escalation or code execution.
- Exploited in the wild
- Not known
- Login needed
- Any signed-in user
- Attackable
- Local or same network only
- Victim action needed
- Not needed
- Fix
- Available
What is CVE-2026-53081?
CVE-2026-53081 is a high-severity vulnerability in Linux kernel, published on 24 Jun 2026. It can only be exploited from the same machine or local network, with no action from the victim.
Official description
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.
Weakness: CWE-386
Which versions are affected by CVE-2026-53081?
It affects 1 product.
Products include Linux kernel.
How do I fix CVE-2026-53081?
Apply the vendor's patch.
Is CVE-2026-53081 being exploited?
There is no known exploitation of CVE-2026-53081 in the wild and no public exploit code.
Other vulnerabilities in Linux kernel
Sources
Also known as BELL-CVE-2026-53081, DEBIAN-CVE-2026-53081, GHSA-phj2-v9xx-8m7r, UBUNTU-CVE-2026-53081.