VulnerabilityPublished 24 Apr 2026Updated 19 Oct 2026

CVE-2026-31638: Linux kernel · NULL Pointer Dereference

Affects Linux kernelSource CVE Database V5

Not known to be exploited · CVSS 7.5 High · fixed in b8f66447448d6c305a51413a67ec8ed26aa7d1dd : patch Linux kernel soon.

Data as of 26 Oct 2026, 17:30 UTC

CVSS 3.1 base score

7.5High

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

EPSS

0.4% chance of exploitation in 30 days – higher than 38% of CVEsExploit Prediction Scoring System: the likelihood attackers will use this flaw soon.

Exploitation: No evidence of active exploitation and no public proof of concept
Automatable: Attackers can reliably automate steps 1–4 of the kill chain
Technical impact: Limited control over the software or limited information exposure

CISA SSVC assessment, 2026-10-16.

Patch

Available – fixed in b8f66447448d6c305a51413a67ec8ed26aa7d1dd, 8299ca146489664e3c0c90a3b8900d8335b1ede4, 6331f1b24a3e85465f6454e003a3e6c22005a5c5 +2

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

Attack Vector: Network
Attack Complexity: Low
Privileges Required: None
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: Network: The vulnerable component is bound to the network stack and the set of possible attackers extends beyond the other options listed, up to and including the entire Internet. Such a vulnerability is often termed 'remotely exploitable' and can be thought of as an attack being exploitable at the protocol level one or more network hops away (e.g., across one or more routers).
Attack Complexity: Low: Specialized access conditions or extenuating circumstances do not exist. An attacker can expect repeatable success against the vulnerable component.
Privileges Required: None: The attacker is unauthorized prior to attack, and therefore does not require any access to settings or files to carry out an attack.
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 24 Apr 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.

What to do

Upgrade to a fixed release listed under Affected software.

Affected software

Product	Affected	Fixed in
LinuxLinux	Affected ≥ 5e6ef4f1017c7f844e305283bbd8875af475e2fc, < b8f66447448d6c305a51413a67ec8ed26aa7d1dd	Fixed in b8f66447448d6c305a51413a67ec8ed26aa7d1dd
LinuxLinux	Affected ≥ 5e6ef4f1017c7f844e305283bbd8875af475e2fc, < 8299ca146489664e3c0c90a3b8900d8335b1ede4	Fixed in 8299ca146489664e3c0c90a3b8900d8335b1ede4
LinuxLinux	Affected ≥ 5e6ef4f1017c7f844e305283bbd8875af475e2fc, < 6331f1b24a3e85465f6454e003a3e6c22005a5c5	Fixed in 6331f1b24a3e85465f6454e003a3e6c22005a5c5
LinuxLinux	Affected ≥ 5e6ef4f1017c7f844e305283bbd8875af475e2fc, < 9fb09861e2b8d1abfe2efaf260c9f1d30080ea38	Fixed in 9fb09861e2b8d1abfe2efaf260c9f1d30080ea38
LinuxLinux	Affected ≥ 5e6ef4f1017c7f844e305283bbd8875af475e2fc, < 0c156aff8a2d4fa0d61db7837641975cf0e5452d	Fixed in 0c156aff8a2d4fa0d61db7837641975cf0e5452d
LinuxLinux	Affected =6.2	Fixed in–

AI-suggested

A fix is available and has been applied in the Linux kernel versions identified by the provided commit hashes. Users should update to a patched kernel version containing these fixes to remediate the vulnerability.

Description

CVE-2026-31638 is a high-severity vulnerability in the Linux kernel's rxrpc subsystem. It involves improper handling of call references when processing to-client packets after the client call has been torn down. This flaw can cause a kernel crash due to an unconditional call to release a non-existent call reference. The issue has been fixed by ensuring the call reference is only dropped if it was actually acquired.

CWE-476NULL Pointer Dereference (opens in a new tab)
Base weaknessLikelihood of exploit: MediumCWE Top 25 (2025): #13OWASP Top 10 A10:2025: Mishandling of Exceptional Conditions (opens in a new tab)
The product dereferences a pointer that it expects to be valid but is NULL.
Implementation
For any pointers that could have been modified or provided from a function that can return NULL, check the pointer for NULL before use. When working with a multithreaded or otherwise asynchronous environment, ensure that proper locking APIs are used to lock before the check, and unlock when it has finished.
Requirements
Select a programming language that is not susceptible to these issues.
Implementation
Check the results of all functions that return a value and verify that the value is non-null before acting upon it.
OWASP Cheat Sheets
Logging (opens in a new tab)
Error Handling (opens in a new tab)
OWASP ASVS 4.0.3
V11.1.7 (opens in a new tab)
From MITRE CWE, MITRE CAPEC and OWASP (Top 10, OpenCRE).

References

Community reviews

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Exploitation evidence

What to do

Affected software

Description

AI analysisMachine-generated, updated 26 Oct 2026, 13:43 UTC

WeaknessesCWE-476

Technical details

References

Community reviews

Related threats