CVE-2026-112912 tox-dev CVE debrief

Who should care

Defenders responsible for Python environments using the filelock package should assess exposure and prioritize upgrading to version 4.2.1 or later. Defenders should verify affected versions and upgrade to 4.2.1 or later. The vulnerability can be exploited by a local user, potentially leading to unauthorized information disclosure.

Why it matters

A vulnerability in filelock's SoftFileLock class allows local users to infer path existence and writability, potentially leading to unauthorized information disclosure. Defenders should verify affected versions and upgrade to 4.2.1 or later.

• Path existence and writability inference by local users
• Potential for unauthorized information disclosure
• Need for verification of affected versions in environment
• Upgrade to fixed version 4.2.1 or later

Technical summary

The SoftFileLock class in the filelock Python package is vulnerable to a symlink swap attack, allowing a local user to infer whether a chosen path exists and is writable. This issue is fixed in version 4.2.1. The vulnerability can be exploited by a local user, potentially leading to unauthorized information disclosure. The vulnerability affects filelock versions from 3.32.6 until 4.2.1. Defenders should verify the existence of affected filelock versions in their environments and upgrade to version 4.2.1 or later. The vulnerability is caused by the SoftFileLock class following a swapped symbolic link during the conditional os.access writability check for a node without its owner-write bit.

Defensive priority

Defenders should prioritize verifying the existence of affected filelock versions in their environments and upgrading to version 4.2.1 or later.

Recommended defensive actions

• Verify the existence of affected filelock versions in your environment.
• Upgrade to filelock version 4.2.1 or later.
• Review and update relevant documentation and configurations.
• 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.
• Confirm whether affected product deployments exist in managed environments and assign an owner for follow-up.
• Review the supplied official advisory or CVE record to validate affected scope, severity, and vendor guidance.

Evidence notes

The CVE record and source item provide details on the vulnerability, including its description, affected versions, and fixed version. The vulnerability affects filelock versions from 3.32.6 until 4.2.1. The issue is fixed in version 4.2.1. Defenders should verify the existence of affected filelock versions in their environments and review relevant documentation and configurations.

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.