VulnerabilityPublished 22 Apr 2026Updated 5 Aug 2026

CVE-2026-31477: Linux kernel · ksmbd: fix memory leaks and NULL deref in smb2_lock()

Affects Linux kernelSource GCVE Database

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Not known to be exploited · CVSS 7.5 High.

Data as of 12 Nov 2026, 03:34 UTC

CVSS 3.1 base score

7.5High

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

Thin evidence

One scorer or none

CVSS scores by source
CNA (Linux)	CVSS 3.1	7.5

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 22 Apr 2026
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 11 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.

What to do

AI-suggested

A fix for this vulnerability has been implemented in the Linux kernel. Users should apply the official Linux kernel updates that include this patch to resolve the memory leak and NULL dereference issues in smb2_lock(). Since no cloud service is involved, manual patching is required. There are no vendor advisories indicating that no action is required or that the issue is already mitigated.

Description

CVE-2026-31477 addresses memory leaks and a NULL pointer dereference in the smb2_lock() function of the Linux kernel's ksmbd component. The vulnerability involves improper error handling after detaching smb_lock from the lock list, leading to resource leaks and potential kernel crashes. The issue was identified through call-graph analysis and fixed by improving cleanup and error propagation logic.

Impact

The vulnerability can cause memory leaks and kernel NULL pointer dereferences leading to system instability or crashes, impacting availability. There is no reported impact on confidentiality or integrity. Exploitation could result in denial of service conditions on affected Linux systems running ksmbd.

Summary

This vulnerability in the Linux kernel's ksmbd smb2_lock() function involves three error handling flaws after list_del() detaches smb_lock from lock_list at no_check_cl. First, if vfs_lock_file() returns an unexpected error in the non-UNLOCK path, smb_lock and its flock are leaked because the cleanup handler does not free detached locks. Second, if vfs_lock_file() returns -ENOENT in the UNLOCK path, similar leaks occur and an incorrect error code is returned. Third, in the rollback path, smb_flock_init() can return NULL on allocation failure, which is then dereferenced, causing a kernel NULL pointer dereference crash. The fix involves consolidating lock freeing before error checks, propagating correct error codes, and adding NULL checks to prevent crashes. The vulnerability has a CVSS 3.1 score of 7.5 (high severity) with no confidentiality or integrity impact but with high availability impact due to potential kernel crashes.

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Exploitation evidence

What to do

Description

AI analysisMachine-generated, updated 12 Nov 2026, 03:34 UTC

Technical details

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