CVE-2026-112940 tox-dev CVE debrief

Who should care

Defenders responsible for securing the filelock library and ensuring the security of the directory holding the lock database should be aware of this vulnerability. This includes operators, platform administrators, vulnerability management teams, and security teams who need to verify the integrity of the filelock library and ensure that the directory holding the lock database is secure. Additionally, defenders should prioritize verifying the integrity of

Why it matters

CVE-2026-112940 is a high-severity vulnerability in the filelock library that allows local users to overwrite or unlink files owned by the lock user. Defenders should prioritize verifying the integrity of the filelock library and ensuring the security of the directory holding the lock database.

• Local users may be able to overwrite or unlink files owned by the lock user
• The vulnerability requires local access to the system
• The vulnerability can be exploited by creating or renaming entries in the directory holding the lock database

Technical summary

The filelock library is vulnerable to a high-severity attack due to its use of SQLite. The ReadWriteLock and AsyncReadWriteLock hand SQLite a name they do not control, allowing a local user to create or rename entries in the directory holding the lock database to make the lock user's process overwrite or unlink its own files. On Linux, the lock validates its database through a descriptor, then connects SQLite to /proc/self/fd/<n>, a Linux path that names the process's own open file n. SQLite turns that path back into a plain path and reopens it by name, following symlinks. This allows another local user who can create or rename entries in the directory that holds the lock database to turn this against the user

Defensive priority

Defenders should prioritize verifying the integrity of the filelock library and ensuring that the directory holding the lock database is secure.

Recommended defensive actions

• Verify the integrity of the filelock library
• Ensure the directory holding the lock database is secure
• Review and update the filelock library to version 4.2.1 or later
• Confirm whether affected product deployments exist in managed environments and assign an owner for follow-up
• Review compensating controls for exposed systems while remediation is scheduled and verified
• Check relevant monitoring, detection, and logs for exposed assets that need extra review
• Track exceptions, retest remediated assets, and close the item only after evidence is documented

Evidence notes

The vulnerability is caused by the ReadWriteLock and AsyncReadWriteLock handing SQLite a name they do not control. On Linux, the lock validates its database through a descriptor, then connects SQLite to /proc/self/fd/<n>, a Linux path that names the process's own open file n. SQLite turns that path back into a plain path and reopens it by name, following symlinks.

Sources and references

Methodology and review provenance

AI-assisted synthesis based on stored public vulnerability evidence. System validation, approval state, and publication status do not by themselves establish human review of this revision. PatchSiren helps prioritize defensive review and does not prove exposure or remediation on any system.