VulnerabilityPublished 26 Jun 2026Updated 6 Jul 2026

CVE-2026-53321: Linux kernel · io_uring/napi: cap busy_poll_to 10 msec

Source GCVE Database

Authoritative record:CVE-2026-53321

Not known to be exploited · CVSS 5.5 Medium · fixed in df8599ee18c0e5fe343ffe0b4c379636b8bb839a : update Linux kernel when convenient.

Data as of 26 Oct 2026, 14:05 UTC

CVSS 3.1 base score

5.5Medium

How severe the flaw is on the 0–10 CVSS scale.

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 – fixed in df8599ee18c0e5fe343ffe0b4c379636b8bb839a, cb3af525f8dfb8930f0c123e5755fa967a12d5c1, 42785efe813e5a7d815f3b6be126e1bc0d12d2b6 +1

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

Attack Vector: Local
Attack Complexity: Low
Privileges Required: Low
User Interaction: None
Scope: Unchanged
Confidentiality: None
Integrity: None
Availability: High

Bold values are the worst case: easiest to exploit or largest impact.

Attack Vector: Local: The vulnerable component is not bound to the network stack and the attacker’s path is via read/write/execute capabilities. Either: the attacker exploits the vulnerability by accessing the target system locally (e.g., keyboard, console), or remotely (e.g., SSH); or the attacker relies on User Interaction by another person to perform actions required to exploit the vulnerability (e.g., tricking a legitimate user into opening a malicious document).
Attack Complexity: Low: Specialized access conditions or extenuating circumstances do not exist. An attacker can expect repeatable success against the vulnerable component.
Privileges Required: Low: The attacker is authorized with (i.e., requires) privileges that provide basic user capabilities that could normally affect only settings and files owned by a user. Alternatively, an attacker with Low privileges may have the ability to cause an impact only to non-sensitive resources.
User Interaction: None: The vulnerable system can be exploited without any interaction from any user.
Scope: Unchanged: An exploited vulnerability can only affect resources managed by the same security authority. In this case, the vulnerable component and the impacted component are either the same, or both are managed by the same security authority.
Confidentiality: None: There is no loss of confidentiality within the impacted component.
Integrity: None: There is no loss of integrity within the impacted component.
Availability: High: There is total loss of availability, resulting in the attacker being able to fully deny access to resources in the impacted component; this loss is either sustained (while the attacker continues to deliver the attack) or persistent (the condition persists even after the attack has completed). Alternatively, the attacker has the ability to deny some availability, but the loss of availability presents a direct, serious consequence to the impacted component (e.g., the attacker cannot disrupt existing connections, but can prevent new connections; the attacker can repeatedly exploit a vulnerability that, in each instance of a successful attack, leaks a only small amount of memory, but after repeated exploitation causes a service to become completely unavailable).

Definitions: FIRST CVSS v3.1 specification.

Exploitation 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.

Disclosed: The CVE record is public on cve.org. Its publication is t = 0.
Detectable: A public nuclei template can find exposed instances, for defenders and attackers alike.
Weaponised: Public exploit code exists in Metasploit or Exploit-DB, or CISA SSVC or the CVSS exploit maturity reports a public proof of concept.
Exploited in the wild: CISA KEV lists it, CISA SSVC rates exploitation active, or a source reports attacks.
Observed by OffSeq Mirage: OffSeq Mirage honeypot sensors recorded attack traffic for this CVE, or found exposed hosts without attack traffic.

Moments are spaced evenly, not to scale; a dashed line marks a gap of six months or more. Deltas count from t = 0. Sources that give only a date (CISA KEV, Exploit-DB, or a time of exactly 00:00Z) read “same day” rather than hours. Metasploit modules carry the flaw’s disclosure date, not their release date, and nuclei templates carry no date, so both appear above but not on the timeline.

ghsa-g22f-3wv9-pgvj

What to do

Upgrade Linux kernel to df8599ee18c0e5fe343ffe0b4c379636b8bb839a, cb3af525f8dfb8930f0c123e5755fa967a12d5c1, 42785efe813e5a7d815f3b6be126e1bc0d12d2b6 or 39767f944a8c9e696566c37ad5b20131406c4b8d.

Affected software

Product	Affected	Fixed in
LinuxLinux	Affected ≥ 8d0c12a80cdeb80d5e0510e96d38fe551ed8e9b5, < df8599ee18c0e5fe343ffe0b4c379636b8bb839a	Fixed in df8599ee18c0e5fe343ffe0b4c379636b8bb839a
LinuxLinux	Affected ≥ 8d0c12a80cdeb80d5e0510e96d38fe551ed8e9b5, < cb3af525f8dfb8930f0c123e5755fa967a12d5c1	Fixed in cb3af525f8dfb8930f0c123e5755fa967a12d5c1
LinuxLinux	Affected ≥ 8d0c12a80cdeb80d5e0510e96d38fe551ed8e9b5, < 42785efe813e5a7d815f3b6be126e1bc0d12d2b6	Fixed in 42785efe813e5a7d815f3b6be126e1bc0d12d2b6
LinuxLinux	Affected ≥ 8d0c12a80cdeb80d5e0510e96d38fe551ed8e9b5, < 39767f944a8c9e696566c37ad5b20131406c4b8d	Fixed in 39767f944a8c9e696566c37ad5b20131406c4b8d
LinuxLinux	Affected =6.9	Fixed in–

AI-suggested

A fix has been implemented in the Linux kernel to cap the busy polling time to 10 milliseconds. Users should apply the official kernel update that includes this change to mitigate the issue. Patch status is not explicitly confirmed in the provided data; therefore, check the vendor advisory for current remediation guidance.

Description

In the Linux kernel, the following vulnerability has been resolved: io_uring/napi: cap busy_poll_to 10 msec Currently there's no cap on the maximum amount of time that napi is allowed to poll if no events are found, which can lead to kernel complaints on a task being stuck as there's no conditional rescheduling done within that loop. Just cap it to 10 msec in total, that's already way above any kind of sane value that will reap any benefits, yet low enough that it's nowhere near being able to trigger preemption complaints.

Impact

This vulnerability does not affect confidentiality or integrity but can impact availability by causing kernel complaints about tasks being stuck due to excessive busy polling without rescheduling. This may degrade system responsiveness or stability under certain workloads.

Summary

The Linux kernel's io_uring napi subsystem previously lacked a cap on the maximum duration that napi could busy poll when no events were found. This unbounded polling could cause the kernel to report tasks as stuck due to the absence of conditional rescheduling within the polling loop. The vulnerability was resolved by introducing a cap of 10 milliseconds on busy polling time, which is sufficiently long to maintain performance benefits but short enough to prevent preemption complaints.

References

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