CVE-2026-53321: Linux kernel · io_uring/napi: cap busy_poll_to 10 msec
Affects Linux kernelSource GCVE Database
Not known to be exploited · CVSS 5.5 Medium · patch available : update Linux kernel when convenient.
Data as of 26 Oct 2026, 13:47 UTC
- EPSS
- 0.1% chance of exploitation in 30 days – higher than 5% of CVEsExploit Prediction Scoring System: the likelihood attackers will use this flaw soon.
- Patch
- Available
CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:HExploitation evidence
Disclosed: evidence found.
CVE published 26 Jun 2026
Detectable: no evidence on record.
No public nuclei template indexed
Weaponised: no evidence on record.
No public exploit code indexed in Metasploit or Exploit-DB
Exploited in the wildExploited: no evidence on record.
Not in CISA KEV and no source reports exploitation
Observed by OffSeq MirageSeen by Mirage: no evidence on record.
No attack traffic recorded by OffSeq Mirage sensors
A missing step is not evidence of safety. Sources: cve.org (opens in a new tab), the Metasploit, Exploit-DB and nuclei-templates index as of 26 Oct 2026.
What to do
Affected software
| Product | Affected | Fixed in |
|---|---|---|
Ubuntu 26.04 LTSlinuxpkg:deb/ubuntu/linux@7.0.0-28.28?arch=source&distro=resoluteOther threats | Affected
| Fixed in– |
Ubuntu 26.04 LTSlinux-awspkg:deb/ubuntu/linux-aws@7.0.0-1008.8?arch=source&distro=resoluteOther threats | Affected
| Fixed in– |
Ubuntu 26.04 LTSlinux-azurepkg:deb/ubuntu/linux-azure@7.0.0-1009.9?arch=source&distro=resoluteOther threats | Affected
| Fixed in– |
Ubuntu 26.04 LTSlinux-azure-fdepkg:deb/ubuntu/linux-azure-fde@7.0.0-1008.8?arch=source&distro=resoluteOther threats | Affected
| Fixed in– |
Ubuntu 26.04 LTSlinux-gcppkg:deb/ubuntu/linux-gcp@7.0.0-1008.8?arch=source&distro=resoluteOther threats | Affected
| Fixed in– |
Ubuntu 26.04 LTSlinux-gkepkg:deb/ubuntu/linux-gke@7.0.0-1003.4?arch=source&distro=resoluteOther threats | Affected
| Fixed in– |
Check your own hosts for these packages with threat-finder (opens in a new tab), our free open-source scanner.
AI-suggested
An official patch is available and should be applied to affected systems. Ubuntu has released security updates addressing this issue as part of USN-8566-1. Users should update their linux-hwe-edge kernel packages to the fixed versions to remediate this vulnerability.
Description
A vulnerability in the Linux kernel's io_uring/napi subsystem allowed the busy_poll_to parameter to have no maximum cap on polling duration, potentially causing kernel complaints about tasks being stuck due to lack of conditional rescheduling. This issue has been resolved by capping the polling time to 10 milliseconds, balancing performance and system stability. The vulnerability affects multiple versions of the linux-hwe-edge kernel prior to specific fixed releases. The issue has a medium severity rating with a CVSS score of 5.5 and does not impact confidentiality or integrity but can cause availability issues. A patch is available and has been released by Ubuntu as part of their security updates.
References
- ubuntu.com/security/CVE-2026-53321 (opens in a new tab)
- cve.org/CVERecord?id=CVE-2026-53321 (opens in a new tab)
- git.kernel.org/linus/df8599ee18c0e5fe343ffe0b4c379636b8bb839a (opens in a new tab)
- git.kernel.org/stable/c/39767f944a8c9e696566c37ad5b20131406c4b8d (opens in a new tab)
- git.kernel.org/stable/c/cb3af525f8dfb8930f0c123e5755fa967a12d5c1 (opens in a new tab)
- git.kernel.org/stable/c/df8599ee18c0e5fe343ffe0b4c379636b8bb839a (opens in a new tab)
- ubuntu.com/security/notices/USN-8566-1 (opens in a new tab)
- ubuntu.com/security/notices/USN-8568-1 (opens in a new tab)
- ubuntu.com/security/notices/USN-8569-1 (opens in a new tab)
- ubuntu.com/security/notices/USN-8593-1 (opens in a new tab)
- ubuntu.com/security/notices/USN-8603-1 (opens in a new tab)
- ubuntu.com/security/notices/USN-8618-1 (opens in a new tab)
- ubuntu.com/security/notices/USN-8663-1 (opens in a new tab)
- ubuntu.com/security/notices/USN-8664-1 (opens in a new tab)
- ubuntu.com/security/notices/USN-8728-1 (opens in a new tab)