CVE-2021-38503
10.0
CRITICAL · CVSS 3.1 · EPSS 4.1% (pctl 91)
In your normal cycle
Critical by CVSS (10), but no sign of active exploitation.
Description
The iframe sandbox rules were not correctly applied to XSLT stylesheets, allowing an iframe to bypass restrictions such as executing scripts or navigating the top-level frame. This vulnerability affects Firefox < 94, Thunderbird < 91.3, and Firefox ESR < 91.3.
Scoring
| CVSS | 10.0 (CRITICAL, v3.1) |
|---|---|
| Vector | CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:H/I:H/A:H |
| EPSS | 4.12% — more likely to be exploited than 91% of all CVEs |
| Weakness | CWE-863 |
| On CISA KEV | no |
| Public exploit | none known |
| Published | 2021-12-08 |
| Last modified | 2026-06-17 |
Affected (4)
| Vendor | Product |
|---|---|
| debian | debian linux |
| mozilla | firefox |
| mozilla | firefox esr |
| mozilla | thunderbird |
References
- https://bugzilla.mozilla.org/show_bug.cgi?id=1729517
- https://lists.debian.org/debian-lts-announce/2021/12/msg00030.html
- https://lists.debian.org/debian-lts-announce/2022/01/msg00001.html
- https://security.gentoo.org/glsa/202202-03
- https://security.gentoo.org/glsa/202208-14
- https://www.debian.org/security/2021/dsa-5026
- https://www.debian.org/security/2022/dsa-5034
- https://www.mozilla.org/security/advisories/mfsa2021-48/
- https://www.mozilla.org/security/advisories/mfsa2021-49/
- https://www.mozilla.org/security/advisories/mfsa2021-50/
- https://bugzilla.mozilla.org/show_bug.cgi?id=1729517
- https://lists.debian.org/debian-lts-announce/2021/12/msg00030.html
- https://lists.debian.org/debian-lts-announce/2022/01/msg00001.html
- https://security.gentoo.org/glsa/202202-03
- https://security.gentoo.org/glsa/202208-14
- https://www.debian.org/security/2021/dsa-5026
- https://www.debian.org/security/2022/dsa-5034
- https://www.mozilla.org/security/advisories/mfsa2021-48/
- https://www.mozilla.org/security/advisories/mfsa2021-49/
- https://www.mozilla.org/security/advisories/mfsa2021-50/
→ the Explorer · watch your stack · NVD