VulnerabilityPublished 25 Jul 2025Updated 19 Nov 2025

CVE-2025-38453: Linux kernel · io_uring/msg_ring: ensure io_kiocb freeing is deferred for RCU

Source GCVE Database

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Not known to be exploited · CVSS 5.5 Medium.

Data as of 13 Nov 2026, 20:33 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 25 Jul 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 13 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-9gq9-xvp8-xm4m

What to do

AI-suggested

A fix is available that defers freeing of io_kiocb requests using RCU mechanisms (kfree_rcu). Users should update to a Linux kernel version that includes this patch. Since this is a kernel-level fix, applying the official kernel update is the recommended remediation. No other mitigation steps are indicated.

Description

CVE-2025-38453 is a medium-severity vulnerability in the Linux kernel's io_uring subsystem related to the msg_ring component. The issue involves improper timing of freeing io_kiocb requests, which can lead to use-after-free conditions detected by Kernel Address Sanitizer (KASAN). The fix defers freeing these requests using RCU mechanisms to ensure safe memory reclamation.

Impact

The vulnerability can cause use-after-free conditions in the kernel, leading to potential instability or crashes (denial of service) as indicated by KASAN reports. There is no indication of confidentiality or integrity impact. The CVSS score is 5.5 (medium), reflecting local attack vector with low complexity and no user interaction required, but only availability impact.

Summary

This vulnerability affects the Linux kernel's io_uring/msg_ring implementation where io_kiocb requests are freed prematurely without proper deferral for Read-Copy-Update (RCU). Syzbot reports indicated that local task_work additions via msg_ring could access requests that have already been freed, causing KASAN to report use-after-free errors. The root cause is that msg_ring requests allocate and free memory independently, requiring deferred freeing. The patch adds an rcu_head and replaces direct kfree calls with kfree_rcu() in the relevant code paths, ensuring that freeing is deferred until it is safe. This fix addresses the issue without introducing other side effects beyond resolving KASAN complaints.

References

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