Thunderbird's update mechanism allowed a medium-integrity user process to interfere with the SYSTEM-level updater by manipulating the file-locking behavior. By injecting code into the user-privileged process, an attacker could bypass intended access controls, allowing SYSTEM-level file operations on paths controlled by a non-privileged user and enabling privilege escalation. This vulnerability affects Firefox < 138, Firefox ESR < 128.10, Firefox ESR < 115.23, Thunderbird < 138, and Thunderbird < 128.10.
The product uses external input to construct a pathname that is intended to identify a file or directory that is located underneath a restricted parent directory, but the product does not properly neutralize special elements within the pathname that can cause the pathname to resolve to a location that is outside of the restricted directory.
| Link | Tags |
|---|---|
| https://bugzilla.mozilla.org/show_bug.cgi?id=1917536 | permissions required |
| https://www.mozilla.org/security/advisories/mfsa2025-28/ | vendor advisory |
| https://www.mozilla.org/security/advisories/mfsa2025-29/ | vendor advisory |
| https://www.mozilla.org/security/advisories/mfsa2025-30/ | vendor advisory |
| https://www.mozilla.org/security/advisories/mfsa2025-31/ | vendor advisory |
| https://www.mozilla.org/security/advisories/mfsa2025-32/ | vendor advisory |