CVE-2026-52933

io_uring/poll: fix signed comparison in io_poll_get_ownership()

HIGH
7.8
CVSS Score
Published: June 24, 2026 at 07:14 AM UTC
Updated: October 19, 2026 at 08:18 PM UTC
4 products affected across 2 vendorsLinux KernelSIMATIC S7-1500 CPU 1518-4 Pn /dp MFP FirmwareSiplus S7-1500 CPU 1518-4 Pn /dp MFP Firmware

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Severity
HIGH7.8
Exploit prediction
EPSS 0.1%
SSVC
No known exploit

Description

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.

Affected

Our own answer: ranges merged, affected separated from platform-only, with confidence and review flags.

5.15.82 ≤ v < 5.166.0.11 ≤ v < 6.16.1.1 ≤ v < 6.1.1756.13 ≤ v < 6.18.276.19 ≤ v < 7.0.46.2 ≤ v < 6.6.1406.7 ≤ v < 6.12.864b702b7d11ce1b9d26fc6d7c5a7ef4ac1d4550485.15.826.0.116.16.1 rc76.1 rc8a26a35e9019fd70bf3cf647dcfdae87abc7baceabc4e6ee16778149811333a969a7a893d4cc110c5
Vendor states this is fixed in 326941b22806cbf2df1fbfe902b7908b368cce42 (fixed)
Vendor states this is fixed in 81bf96b0abbfa4cd47ea32e12596aed3855fb2f3 (fixed)
Vendor states this is fixed in c6d191164dc81838d8dbf452a6000f68c558d1ae (fixed)
Vendor states this is fixed in cf522703d4f194991615763697ae25a3f9539763 (fixed)
Vendor states this is fixed in ea0697129807d718037f618221037aa0660ee3c5 (fixed)
Vendor states this is fixed in fc47043f3d9af3efa407665b47f8378ec691ba18 (fixed)
Affected range stops below 5.16, so it looks safe — our inference, not a vendor statement
Vendor states this is fixed in 6.1 (unaffected)
Vendor states this is fixed in 6.1.175 (unaffected)
Vendor states this is fixed in 6.12.86 (unaffected)
Vendor states this is fixed in 6.18.27 (unaffected)
Vendor states this is fixed in 6.6.140 (unaffected)
Vendor states this is fixed in 7.0.4 (unaffected)
Vendor states this is fixed in 7.1 (unaffected)

SSVC — Action Prioritization

SSVCNo known exploitNot automatableTotal impact

SSVC signals action urgency (what to patch first), separate from CVSS which measures severity.

CVSS

7.8HIGHLinux
Vector?

Quick Info

StatusMODIFIED
CWE
CWE-835CWE-190

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