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CVE-2026-99227

io_uring/waitid: prevent cancel reference wrap

No exploitation reported by the sources we read.

  • Published2026-11-02

Am I affected?

With a domain, we read the version its public headers and pages expose. A distribution build can carry the fix under an older number.

Description

In the Linux kernel, the following vulnerability has been resolved: io_uring/waitid: prevent cancel reference wrap io_waitid packs the cancellation state into bit 31 of ->refs and uses bits 30:0 as a 31-bit reference counter: #define IO_WAITID_CANCEL_FLAG BIT(31) #define IO_WAITID_REF_MASK GENMASK(30, 0) __io_waitid_cancel() marks a request canceled, then increments the low bits of ->refs to claim completion ownership. When another path owns the request, the increment remains even though cancellation returns false. The request remains discoverable by cancellation, so repeated failed attempts can wrap the 31-bit reference field to zero. A later cancellation can claim ownership and complete the request a second time. Use atomic_fetch_or() when setting the cancel flag and inspect the old flag value. The first cancel attempt continues to the existing ownership increment, preserving its wake and issuer handoff semantics. Later attempts see the cancel flag and return without incrementing the reference field. This makes repeated failed cancellation attempts idempotent while leaving the first-cancel state transitions unchanged.

Timeline

dates in UTC
  1. 2026-11-0216:06CVE publishedCNA

Observed activity

isMalicious corpus · updated 2026-11-02 15:37 UTC
Indicators tagged with this CVE, per day0 indicators over 7 days
Block these indicators
  • Firewall list (EDL, text): https://api.ismalicious.com/edl/cve/CVE-2026-99227?format=txt
  • CSV export: https://api.ismalicious.com/edl/cve/CVE-2026-99227?format=csv
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Versions per branch

Products declared by the CNA

As Linux, the CNA that assigned this CVE, declared them in the CVE record; versions as written. NVD lists no product for this CVE yet: this is the only product data so far.

  • Linuxother versions: not affected

    https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git

    Affected
    • ≥ f31ecf671ddc498f20219453395794ff2383e06b, < 20b67288574c7c3df6b8ea7ed3b7af90a868006ffixed in 20b67288574c7c3df6b8ea7ed3b7af90a868006fgit
    • ≥ f31ecf671ddc498f20219453395794ff2383e06b, < 5bfeee1774791602a0d53eb717f00f172127a017fixed in 5bfeee1774791602a0d53eb717f00f172127a017git
    • ≥ f31ecf671ddc498f20219453395794ff2383e06b, < 857aa2012b91cad6fdef54a4b6c632d9d0b6e64ffixed in 857aa2012b91cad6fdef54a4b6c632d9d0b6e64fgit
    • ≥ f31ecf671ddc498f20219453395794ff2383e06b, < 22fb4a4518e305164c7f203608287564de292f34fixed in 22fb4a4518e305164c7f203608287564de292f34git
  • Linuxother versions: affected

    https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git

    Affected
    • = 6.7no fix stated

    Not affected < 6.7 · ≥ 6.12.115, ≤ 6.12.* · ≥ 6.18.60, ≤ 6.18.* · ≥ 7.2.14, ≤ 7.2.* · ≥ 7.3.1, ≤ 7.3.*

Source: the CNA record (CVE Program), © The MITRE Corporation,CVE Terms of UseCVE recordupdated 2026-11-02

Neither OSV.dev nor the vendor advisories we read list affected versions for CVE-2026-99227 yet.

Full record on NVD

Fix

No fix published by the sources we read yet. NVD record

Detection

Nuclei template
none so far
ProjectDiscovery
Exploit-DB
no entry
Exploit-DB
Proof-of-concept repositories
none listed
PoC-in-GitHub
Metasploit modules
none listed
Metasploit Framework

Sources

  • NVDCVE record2026-11-02
  • CNACVSS 3.17.82026-11-02

Technical details

CVSS v3 Vector
CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
Published
2026-11-02

Frequently asked questions

What is CVE-2026-99227?

In the Linux kernel, the following vulnerability has been resolved: io_uring/waitid: prevent cancel reference wrap io_waitid packs the cancellation state into bit 31 of ->refs and uses bits 30:0 as a 31-bit reference counter: #define IO_WAITID_CANCEL_FLAG BIT(31) #define IO_WAITID_REF_MASK GENMASK(30, 0) __io_waitid_cancel() marks a request canceled, then increments the low bits of ->refs to claim completion ownership. When another path owns the request, the increment remains even though cancellation returns false. The request remains discoverable by cancellation, so repeated failed attempts can wrap the 31-bit reference field to zero. A later cancellation can claim ownership and complete the request a second time. Use atomic_fetch_or() when setting the cancel flag and inspect the old flag value. The first cancel attempt continues to the existing ownership increment, preserving its wake and issuer handoff semantics. Later attempts see the cancel flag and return without incrementing the reference field. This makes repeated failed cancellation attempts idempotent while leaving the first-cancel state transitions unchanged.

Is CVE-2026-99227 actively exploited?

Active exploitation of CVE-2026-99227 has not been confirmed.

What is the CVSS score for CVE-2026-99227?

CVE-2026-99227 has a CVSS v3 base score of 7.8 (HIGH severity), with vector string CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H.

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