VulnerabilityPublished 1 May 2025Updated 5 Nov 2025

CVE-2025-23154: Linux kernel · io_uring/net: fix io_req_post_cqe abuse by send bundle

Source GCVE Database

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Not known to be exploited · CVSS 5.5 Medium.

Data as of 4 Nov 2026, 18:06 UTC

CVSS 3.1 base score

5.5Medium

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

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 1 May 2025
Detectable: no evidence on record.
No public nuclei template indexed
Weaponized: 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 4 Nov 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.
Weaponized: A Metasploit exploit module or Exploit-DB entry exists (Metasploit scanner modules do not count), 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-f6mf-84fx-cph2

What to do

AI-suggested

A fix for this vulnerability has been implemented in the Linux kernel source code by adding a flag to correctly manage multishot request behavior in io_uring. Users and administrators should update to the fixed kernel version once available. Since no vendor advisory or patch links are provided, check the official Linux kernel repositories or distributions for the patch corresponding to this issue. No other mitigation or workaround is indicated.

Description

A medium-severity vulnerability (CVE-2025-23154) in the Linux kernel's io_uring subsystem involves improper use of the io_req_post_cqe() function. The flaw arises because io_req_post_cqe() was used incorrectly by send bundle requests, which are not multishot requests. This misuse could lead to unintended behavior in the kernel's I/O completion queue handling. The issue has been fixed by adding a flag to distinguish requests that want to post multiple completion queue events (CQEs).

Impact

The vulnerability does not affect confidentiality or integrity but impacts availability, as indicated by the CVSS vector (Availability: High). Improper handling of completion queue events could cause kernel warnings and potentially lead to system instability or denial of service conditions. There is no indication of exploitation in the wild or impact on data confidentiality or integrity.

Summary

CVE-2025-23154 addresses a vulnerability in the Linux kernel's io_uring/net component where the function io_req_post_cqe() was abused by send bundle requests. The function is intended only for multishot requests (REQ_F_APOLL_MULTISHOT), but bundled sends do not qualify as such. This misuse could cause improper posting of completion queue events, potentially leading to kernel instability or denial of service. The fix introduces a new flag to indicate whether a request intends to post multiple CQEs, preventing the misuse. The patch clarifies that eventually REQ_F_APOLL_MULTISHOT will imply this flag, but this was deferred for simplicity.

References

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