The Mozilla Maintenance Service does not guard against files being hardlinked to another file in the updates directory, allowing for the replacement of local files, including the Maintenance Service executable, which is run with privileged access. Additionally, there was a race condition during checks for junctions and symbolic links by the Maintenance Service, allowing for potential local file and directory manipulation to be undetected in some circumstances. This allows for potential privilege escalation by a user with unprivileged local access. Note: These attacks requires local system access and only affects Windows. Other operating systems are not affected.. This vulnerability affects Firefox < 69 and Firefox ESR < 68.1.
Weakness
The product contains a concurrent code sequence that requires temporary, exclusive access to a shared resource, but a timing window exists in which the shared resource can be modified by another code sequence operating concurrently.
Affected Software
| Name | Vendor | Start Version | End Version |
|---|---|---|---|
| Firefox | Mozilla | * | 69.0 (excluding) |
| Firefox_esr | Mozilla | * | 68.1.0 (excluding) |
| Firefox | Ubuntu | upstream | * |
| Mozjs38 | Ubuntu | bionic | * |
| Mozjs38 | Ubuntu | esm-apps/bionic | * |
| Mozjs38 | Ubuntu | upstream | * |
| Mozjs52 | Ubuntu | bionic | * |
| Mozjs52 | Ubuntu | disco | * |
| Mozjs52 | Ubuntu | eoan | * |
| Mozjs52 | Ubuntu | esm-apps/focal | * |
| Mozjs52 | Ubuntu | esm-infra/bionic | * |
| Mozjs52 | Ubuntu | focal | * |
| Mozjs52 | Ubuntu | groovy | * |
| Mozjs52 | Ubuntu | upstream | * |
| Mozjs60 | Ubuntu | disco | * |
| Mozjs60 | Ubuntu | eoan | * |
| Mozjs60 | Ubuntu | upstream | * |
Extended Description
A race condition occurs within concurrent environments, and it is effectively a property of a code sequence. Depending on the context, a code sequence may be in the form of a function call, a small number of instructions, a series of program invocations, etc. A race condition violates these properties, which are closely related:
A race condition exists when an “interfering code sequence” can still access the shared resource, violating exclusivity. The interfering code sequence could be “trusted” or “untrusted.” A trusted interfering code sequence occurs within the product; it cannot be modified by the attacker, and it can only be invoked indirectly. An untrusted interfering code sequence can be authored directly by the attacker, and typically it is external to the vulnerable product.
Potential Mitigations
- Minimize the usage of shared resources in order to remove as much complexity as possible from the control flow and to reduce the likelihood of unexpected conditions occurring.
- Additionally, this will minimize the amount of synchronization necessary and may even help to reduce the likelihood of a denial of service where an attacker may be able to repeatedly trigger a critical section (CWE-400).
Related Attack Patterns
References
- http://lists.opensuse.org/opensuse-security-announce/2019-10/msg00011.html
- http://lists.opensuse.org/opensuse-security-announce/2019-10/msg00017.html
- https://bugzilla.mozilla.org/show_bug.cgi?id=1551913
- https://bugzilla.mozilla.org/show_bug.cgi?id=1552206
- https://www.mozilla.org/security/advisories/mfsa2019-25/
- https://www.mozilla.org/security/advisories/mfsa2019-26/
- http://lists.opensuse.org/opensuse-security-announce/2019-10/msg00011.html
- http://lists.opensuse.org/opensuse-security-announce/2019-10/msg00017.html
- https://bugzilla.mozilla.org/show_bug.cgi?id=1551913
- https://bugzilla.mozilla.org/show_bug.cgi?id=1552206
- https://www.mozilla.org/security/advisories/mfsa2019-25/
- https://www.mozilla.org/security/advisories/mfsa2019-26/