9.8
Critical
CVE-2021-4140 It was possible to construct specific XSLT markup that would be able to bypass an iframe sandbox
Description
It was possible to construct specific XSLT markup that would be able to bypass an iframe sandbox. This vulnerability affects Firefox ESR < 91.5, Firefox < 96, and Thunderbird < 91.5.
Affected products and versions
| Product | Affected versions | Fixed in |
|---|---|---|
| Firefox ESR 91.5 | earliest → < 91.5 | 91.5 |
| Firefox 96 | earliest → < 96 | 96 |
| Thunderbird 91.5 | earliest → < 91.5 | 91.5 |
References
- www.mozilla.org www.mozilla.org
- www.mozilla.org www.mozilla.org
- www.mozilla.org www.mozilla.org
- bugzilla.mozilla.org bugzilla.mozilla.org
Timeline
- Published
- Last modified
Other CVEs of Firefox ESR
The 833 CVEs of Firefox ESR →
CVE-2026-5734
Memory safety bugs present in Firefox ESR 140.9.0, Thunderbird ESR 140.9.0, Firefox 149.0.1 and Thunderbird 149.0.1
8.1
High
CVE-2026-5732
Incorrect boundary conditions, integer overflow in the Graphics: Text component
8.8
High
CVE-2026-5731
Memory safety bugs present in Firefox ESR 115.34.0, Firefox ESR 140.9.0, Thunderbird ESR 140.9.0, Firefox 149.0.1 and…
9.8
Critical
CVE-2026-2447
Heap buffer overflow in libvpx
8.8
High