Under certain conditions, when running the nsDocShell destructor, a race condition can cause a use-after-free. We are aware of targeted attacks in the wild abusing this flaw. This vulnerability affects Thunderbird < 68.7.0, Firefox < 74.0.1, and Firefox ESR < 68.6.1.
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.
The product reuses or references memory after it has been freed. At some point afterward, the memory may be allocated again and saved in another pointer, while the original pointer references a location somewhere within the new allocation. Any operations using the original pointer are no longer valid because the memory "belongs" to the code that operates on the new pointer.
| Link | Tags |
|---|---|
| https://www.mozilla.org/security/advisories/mfsa2020-14/ | vendor advisory |
| https://www.mozilla.org/security/advisories/mfsa2020-11/ | vendor advisory |
| https://bugzilla.mozilla.org/show_bug.cgi?id=1620818 | issue tracking exploit |
| https://usn.ubuntu.com/4335-1/ | third party advisory vendor advisory |