# CVE-2026-52933: io_uring/poll: fix signed comparison in io_poll_get_ownership()

Status: published. Published: 2026-06-24. Updated: 2026-11-10.

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

io_uring/poll: fix signed comparison in io_poll_get_ownership()

io_poll_get_ownership() uses a signed comparison to check whether
poll_refs has reached the threshold for the slowpath:

    if (unlikely(atomic_read(&req->poll_refs) >= IO_POLL_REF_BIAS))

atomic_read() returns int (signed). When IO_POLL_CANCEL_FLAG
(BIT(31)) is set in poll_refs, the value becomes negative in
signed arithmetic, so the >= 128 comparison always evaluates to
false and the slowpath is never taken.

Fix this by casting the atomic_read() result to unsigned int
before the comparison, so that the cancel flag is treated as a
large positive value and correctly triggers the slowpath.

## Remediation

No remediation reported in collected sources

## Affected products and versions

- Linux / Linux: ≥ a26a35e9019fd70bf3cf647dcfdae87abc7bacea; < 81bf96b0abbfa4cd47ea32e12596aed3855fb2f3 (affected, git); ≥ a26a35e9019fd70bf3cf647dcfdae87abc7bacea; < cf522703d4f194991615763697ae25a3f9539763 (affected, git); ≥ a26a35e9019fd70bf3cf647dcfdae87abc7bacea; < fc47043f3d9af3efa407665b47f8378ec691ba18 (affected, git); ≥ a26a35e9019fd70bf3cf647dcfdae87abc7bacea; < ea0697129807d718037f618221037aa0660ee3c5 (affected, git); ≥ a26a35e9019fd70bf3cf647dcfdae87abc7bacea; < c6d191164dc81838d8dbf452a6000f68c558d1ae (affected, git); ≥ a26a35e9019fd70bf3cf647dcfdae87abc7bacea; < 326941b22806cbf2df1fbfe902b7908b368cce42 (affected, git); 4b702b7d11ce1b9d26fc6d7c5a7ef4ac1d455048 (affected, git); bc4e6ee16778149811333a969a7a893d4cc110c5 (affected, git); ≥ 5.15.82; < 5.16 (affected, semver); ≥ 6.0.11; < 6.1 (affected, semver). Source: CNA: Linux
- Linux / Linux: 6.1 (affected); ≥ 0; < 6.1 (unaffected, semver); ≥ 6.1.175; ≤ 6.1.* (unaffected, semver); ≥ 6.6.140; ≤ 6.6.* (unaffected, semver); ≥ 6.12.86; ≤ 6.12.* (unaffected, semver); ≥ 6.18.27; ≤ 6.18.* (unaffected, semver); ≥ 7.0.4; ≤ 7.0.* (unaffected, semver); ≥ 7.1; ≤ * (unaffected, original_commit_for_fix). Source: CNA: Linux
- Siemens / SIMATIC S7-1500 CPU 1518-4 PN/DP MFP (6ES7518-4AX00-1AB0): ≥ V3.1.6; < * (affected, custom). Source: ADP: siemens-SADP
- Siemens / SIMATIC S7-1500 CPU 1518-4 PN/DP MFP (6ES7518-4AX00-1AB0): ≥ V3.1.7; < * (affected, custom). Source: ADP: siemens-SADP
- Siemens / SIMATIC S7-1500 CPU 1518-4 PN/DP MFP (6ES7518-4AX00-1AC0): ≥ V3.1.6; < * (affected, custom). Source: ADP: siemens-SADP
- Siemens / SIMATIC S7-1500 CPU 1518-4 PN/DP MFP (6ES7518-4AX00-1AC0): ≥ V3.1.7; < * (affected, custom). Source: ADP: siemens-SADP
- Siemens / SIMATIC S7-1500 CPU 1518F-4 PN/DP MFP (6ES7518-4FX00-1AB0): ≥ V3.1.6; < * (affected, custom). Source: ADP: siemens-SADP
- Siemens / SIMATIC S7-1500 CPU 1518F-4 PN/DP MFP (6ES7518-4FX00-1AB0): ≥ V3.1.7; < * (affected, custom). Source: ADP: siemens-SADP
- Siemens / SIMATIC S7-1500 CPU 1518F-4 PN/DP MFP (6ES7518-4FX00-1AC0): ≥ V3.1.6; < * (affected, custom). Source: ADP: siemens-SADP
- Siemens / SIMATIC S7-1500 CPU 1518F-4 PN/DP MFP (6ES7518-4FX00-1AC0): ≥ V3.1.7; < * (affected, custom). Source: ADP: siemens-SADP
- Siemens / SIPLUS S7-1500 CPU 1518-4 PN/DP MFP (6AG1518-4AX00-4AC0): ≥ V3.1.6; < * (affected, custom). Source: ADP: siemens-SADP
- Siemens / SIPLUS S7-1500 CPU 1518-4 PN/DP MFP (6AG1518-4AX00-4AC0): ≥ V3.1.7; < * (affected, custom). Source: ADP: siemens-SADP

## Severity and prioritization

- CVSS 3.1: 7.8 (high); CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H; source: CNA: Linux

- CISA KEV: No listing in collected sources

- EPSS: 0.15% as of 2026-11-09; percentile 4.01%

- SSVC: exploitation none; automatable no; technical impact total; source ADP: CISA-ADP

- Weaknesses: CWE-190

## Exploit evidence

No exploit evidence in collected sources. This is not proof of no exploitation.

## References

- https://git.kernel.org/stable/c/81bf96b0abbfa4cd47ea32e12596aed3855fb2f3 (CNA: Linux)

- https://git.kernel.org/stable/c/cf522703d4f194991615763697ae25a3f9539763 (CNA: Linux)

- https://git.kernel.org/stable/c/fc47043f3d9af3efa407665b47f8378ec691ba18 (CNA: Linux)

- https://git.kernel.org/stable/c/ea0697129807d718037f618221037aa0660ee3c5 (CNA: Linux)

- https://git.kernel.org/stable/c/c6d191164dc81838d8dbf452a6000f68c558d1ae (CNA: Linux)

- https://git.kernel.org/stable/c/326941b22806cbf2df1fbfe902b7908b368cce42 (CNA: Linux)

- https://cert-portal.siemens.com/productcert/html/ssa-019113.html (ADP: siemens-SADP)

- https://cert-portal.siemens.com/productcert/html/ssa-457936.html (ADP: siemens-SADP)

## Provenance

- CNA: Linux: https://www.cve.org/CVERecord?id=CVE-2026-52933; retrieved 2026-11-10; source updated 2026-11-10

- FIRST EPSS: https://api.first.org/data/v1/epss?cve=CVE-2026-52933; retrieved 2026-11-10; source updated Not reported

Revision: 927c1ac76a9580adf95e49fc0ad40b24a9b9b3edc08a09ea4de5107051ad68f3

Canonical: https://y2.dev/cve/CVE-2026-52933

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