VulnerabilityPublished 18 Apr 2024Updated 3 Nov 2025

CVE-2024-26921: Linux kernel · inet: inet_defrag: prevent sk release while still in use

Source GCVE Database

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Not known to be exploited · CVSS 5.5 Medium.

Data as of 30 Oct 2026, 00:34 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 18 Apr 2024
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 29 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.
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-4vg2-58j7-gmw7

What to do

AI-suggested

A fix for this vulnerability has been implemented in the Linux kernel. Users should apply the official kernel updates that include this patch to ensure proper handling of socket references during IP fragment reassembly. There is no indication that additional mitigation steps are required beyond applying the updated kernel version containing the fix.

Description

CVE-2024-26921 is a medium severity vulnerability in the Linux kernel's inet_defrag function. It involves improper handling of socket references (skb->sk) during IP fragment reassembly, which can lead to premature socket release while still in use. This affects skb fragments reassembled via netfilter or similar modules such as openvswitch, potentially causing memory accounting issues and impacting packet processing in the transmission pipeline.

Impact

The vulnerability can cause the socket reference to be released while still in use during IP fragment reassembly, leading to potential memory accounting underflows and disruption of packet processing in the transmission pipeline. This can result in denial of service or instability in affected kernel network modules that handle fragmented packets, such as netfilter, openvswitch, or connection tracking components.

Summary

The vulnerability in the Linux kernel inet_defrag function arises because ip_local_out() and related functions pass skb->sk as an argument, and if the skb is a fragment that gets reassembled before the function returns, the socket reference (sk) must not be released prematurely. The issue affects skb fragments reassembled through netfilter or similar modules (e.g., openvswitch or ct_act.c) during transmission. The root cause is that ip_defrag() calls skb_orphan() in the output path, which is problematic because the output path depends on skb->sk remaining valid. The fix involves delaying the orphaning of the socket reference until it is safe, by moving the orphaning logic deeper into the core and adjusting memory accounting to prevent underflow. This ensures that the socket reference is retained correctly during reassembly and only released when appropriate.

References

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