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Vulnerability record · CVE-2026-53081 · published 24 June 2026

CVE-2026-53081: Linux kernel vulnerability

Linux · Linux Kernel

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.

7.8 CVSS 3.1 High EPSS 0.18% · top 93.2% CWE-386 · CWE-386
7.8CVSS 3.1 base score
0.18%EPSS exploitation probability, 30 days
NoNot in CISA KEV
1Affected product versions listed by NVD
7References
23 Jul 2026Last modified by NVD

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.

CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H

Affected products

1 vulnerable configurations from NVD's CPE data, grouped by vendor and product.

References

LinkTags
https://git.kernel.org/stable/c/13c02881e49aac4c82b261faa26db9edf2567231 Patch
https://git.kernel.org/stable/c/2f2ec8e7730e21fc9bd49e0de9cdd58213ea24d0 Patch
https://git.kernel.org/stable/c/691adf738817275368ed56311b7d798d617823a3 Patch
https://git.kernel.org/stable/c/7d73c72cccac651acc891377a5e623e4021c6380 Patch
https://access.redhat.com/security/cve/CVE-2026-53081 Third Party Advisory
https://bugzilla.redhat.com/show_bug.cgi?id=2492322 Third Party Advisory
https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-53081.json Third Party Advisory

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Source: NIST National Vulnerability Database (record CVE-2026-53081), CISA KEV, FIRST EPSS (scores of 2026-09-26). This page is refreshed as NVD updates the record.