CVE-2026-112939VulnerabilityPublished 9 Nov 2026

gam · filelock: SoftFileLock removes a live holder's marker when another user forges the PID in a writable marker

Affects gamSource GCVE Database

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Authoritative record:CVE-2026-112939· Medium 4.7

Not known to be exploited · CVSS 4.7 Medium.

Data as of 9 Nov 2026, 20:03 UTC

CVSS 3.1 base score

4.7Medium

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

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

Attack Vector: Local
Attack Complexity: High
Privileges Required: Low
User Interaction: None
Scope: Unchanged
Confidentiality: None
Integrity: High
Availability: None

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: High: A successful attack depends on conditions beyond the attacker's control. That is, a successful attack cannot be accomplished at will, but requires the attacker to invest in some measurable amount of effort in preparation or execution against the vulnerable component before a successful attack can be expected. For example, a successful attack may require an attacker to: gather knowledge about the environment in which the vulnerable target/component exists; prepare the target environment to improve exploit reliability; or inject themselves into the logical network path between the target and the resource requested by the victim in order to read and/or modify network communications (e.g., a man in the middle attack).
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: High: There is a total loss of integrity, or a complete loss of protection. For example, the attacker is able to modify any/all files protected by the impacted component. Alternatively, only some files can be modified, but malicious modification would present a direct, serious consequence to the impacted component.
Availability: None: There is no impact to availability within the impacted component.

Definitions: FIRST CVSS v3.1 specification.

Exploitation evidence

Disclosed: evidence found.
CVE published 20 Oct 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 9 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

Affected software

Product	Affected	Fixed in
Homebrewgam`pkg:brew/gam`Other threats	Affected >=7.50.00	Fixed in–

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AI-suggested

Users should ensure that the lock marker files are not writable by other users except the lock owner, avoiding group or other write bits on the marker file. Using a restrictive umask such as 022 prevents the vulnerability. Additionally, directories containing lock markers should be sticky or otherwise prevent marker removal by other users. Monitor vendor advisories for any future patches.

Description

A vulnerability in the filelock library versions 3.22.0 through 4.2.0 allows a local user with write access to a lock marker file (but without permission to remove it) to forge the process ID in the marker. This causes the lock to be incorrectly considered stale, enabling two processes to hold the lock simultaneously and potentially corrupt shared data. The issue arises when the marker file is created with group or other write permissions, such as with a permissive mode or a lax umask in a sticky or non-removable directory.

Impact

The vulnerability allows a local attacker with write access to the lock marker file (but not removal rights) to cause the lock to be considered stale and removed improperly. This leads to two processes simultaneously holding the lock and potentially writing concurrently to the protected resource, causing integrity violations. There is no confidentiality or availability impact. The attack requires local access with low privileges and has high attack complexity due to the specific permission and process conditions needed.

Summary

The filelock library's SoftFileLock and related classes rely on a marker file to indicate lock ownership by a process ID (PID). They determine if a lock is stale by reading the PID in the marker file without verifying who wrote it. A local user who can write to the marker file but cannot remove it (due to directory sticky bits or permissions) can overwrite the PID with a dead process ID. When another process of the lock owner's account or root attempts to acquire the lock, it sees the forged PID as stale, removes the live marker, and acquires the lock. This results in two processes concurrently holding the lock, violating mutual exclusion. The vulnerability affects versions 3.22.0 through 4.2.0 and requires specific conditions: writable marker file by another user, sticky or non-removable directory, and a contender process of the lock owner's account or root. The default umask 022 is not affected, but umask 002 or 000 with group write permissions is. The flaw was introduced in version 3.22.0 with the stale lock detection feature that trusts the PID record in the marker file.

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What to do

Affected software

Description

AI analysisMachine-generated, updated 9 Nov 2026, 20:03 UTC

Technical details

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