CVE-2026-53081
bpf: Enforce regsafe base id consistency for BPF_ADD_CONST scalars
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.
INFO
Published Date :
June 24, 2026, 4:30 p.m.
Last Modified :
June 24, 2026, 4:30 p.m.
Remotely Exploit :
No
Source :
Linux
Affected Products
The following products are affected by CVE-2026-53081
vulnerability.
Even if cvefeed.io is aware of the exact versions of the
products
that
are
affected, the information is not represented in the table below.
No affected product recoded yet
Solution
- Apply kernel patches to verify base ID consistency.
- Ensure BPF_ADD_CONST derivatives originate from mapped bases.
- Update affected Linux kernel versions.
- Recompile kernel with updated security checks.
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