Bug 2422884 (CVE-2025-68146)

Summary: CVE-2025-68146 filelock: filelock: Time-of-Check-Time-of-Use (TOCTOU) race condition and symlink attack allows arbitrary file corruption or truncation
Product: [Other] Security Response Reporter: OSIDB Bzimport <bzimport>
Component: vulnerabilityAssignee: Product Security DevOps Team <prodsec-dev>
Status: NEW --- QA Contact:
Severity: medium Docs Contact:
Priority: medium    
Version: unspecifiedCC: adudiak, alinfoot, anpicker, anthomas, aprice, bbrownin, bdettelb, bparees, carogers, caswilli, crizzo, dfreiber, dnakabaa, doconnor, drow, dtrifiro, dymurray, eglynn, ehelms, erezende, ggainey, gtanzill, haoli, hasun, hkataria, ibolton, jajackso, jburrell, jbuscemi, jcammara, jdobes, jfula, jjoyce, jkoehler, jmatthew, jmitchel, jmontleo, jneedle, joehler, jowilson, jsamir, jschluet, juwatts, jwong, kaycoth, kegrant, kgaikwad, koliveir, kshier, lball, lcouzens, lhh, ljawale, lphiri, luizcosta, mabashia, mburns, mgarciac, mhulan, mskarbek, ngough, nmoumoul, nweather, nyancey, oezr, omaciel, ometelka, orabin, osousa, pbraun, pcreech, pgaikwad, ptisnovs, rbobbitt, rbryant, rchan, rjohnson, sdawley, sdoran, shvarugh, simaishi, slucidi, smallamp, smcdonal, sseago, stcannon, syedriko, teagle, tfister, thavo, tmalecek, ttakamiy, veshanka, vkumar, weaton, xdharmai, xiaoxwan, yguenane, zzhou
Target Milestone: ---Keywords: Security
Target Release: ---   
Hardware: All   
OS: Linux   
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A flaw was found in filelock. This vulnerability allows local attackers to corrupt or truncate arbitrary user files via a Time-of-Check-Time-of-Use (TOCTOU) race condition and symlink attacks.
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oVirt Team: --- RHEL 7.3 requirements from Atomic Host:
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Description OSIDB Bzimport 2025-12-16 19:01:39 UTC 
filelock is a platform-independent file lock for Python. In versions prior to 3.20.1, a Time-of-Check-Time-of-Use (TOCTOU) race condition allows local attackers to corrupt or truncate arbitrary user files through symlink attacks. The vulnerability exists in both Unix and Windows lock file creation where filelock checks if a file exists before opening it with O_TRUNC. An attacker can create a symlink pointing to a victim file in the time gap between the check and open, causing os.open() to follow the symlink and truncate the target file. All users of filelock on Unix, Linux, macOS, and Windows systems are impacted. The vulnerability cascades to dependent libraries. The attack requires local filesystem access and ability to create symlinks (standard user permissions on Unix; Developer Mode on Windows 10+). Exploitation succeeds within 1-3 attempts when lock file paths are predictable. The issue is fixed in version 3.20.1. If immediate upgrade is not possible, use SoftFileLock instead of UnixFileLock/WindowsFileLock (note: different locking semantics, may not be suitable for all use cases); ensure lock file directories have restrictive permissions (chmod 0700) to prevent untrusted users from creating symlinks; and/or monitor lock file directories for suspicious symlinks before running trusted applications. These workarounds provide only partial mitigation. The race condition remains exploitable. Upgrading to version 3.20.1 is strongly recommended.