Vulnerability · Published Dec 8, 2021 · Assigned by mozilla
CVE-2021-38503
Critical 10.0
In plain English
A critical-severity security flaw in Firefox from Mozilla. There are no confirmed reports of exploitation so far. The chance it is exploited in the next 30 days is estimated at 4.1% (higher than 91% of all known vulnerabilities). Fixed versions are available - upgrade the affected package.
Severity (CVSS NVD)10.0Critical
Exploit odds (30 days)4.1%top 9.2% of all CVEs
Exploited in the wildNo reportsnot in CISA KEV
Attack toolingNoneno public tooling known
Official 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.
Affected packages & fixed versions
| Ecosystem | Package | Fixed in | Advisory |
|---|---|---|---|
| AlmaLinux:8 | firefox | 91.3.0-1.el8_4.alma | ALSA-2021:4123 |
| AlmaLinux:8 | thunderbird | 91.3.0-2.el8_4.alma | ALSA-2021:4130 |
| AlmaLinux:8 | thunderbird | 91.3.0-2.el8_4.alma.plus | ALSA-2021:4130 |
| Alpine:v3.20 | firefox | 94.0-r0 | ALPINE-CVE-2021-38503 |
| Alpine:v3.21 | firefox | 94.0-r0 | ALPINE-CVE-2021-38503 |
| Alpine:v3.22 | firefox | 94.0-r0 | ALPINE-CVE-2021-38503 |
| Alpine:v3.23 | firefox | 94.0-r0 | ALPINE-CVE-2021-38503 |
| Alpine:v3.20 | firefox-esr | 91.3.0-r0 | ALPINE-CVE-2021-38503 |
| Alpine:v3.21 | firefox-esr | 91.3.0-r0 | ALPINE-CVE-2021-38503 |
| Alpine:v3.22 | firefox-esr | 91.3.0-r0 | ALPINE-CVE-2021-38503 |
| Alpine:v3.23 | firefox-esr | 91.3.0-r0 | ALPINE-CVE-2021-38503 |
| Alpine:v3.21 | librewolf | 94.0-r0 | ALPINE-CVE-2021-38503 |
| Alpine:v3.22 | librewolf | 94.0-r0 | ALPINE-CVE-2021-38503 |
| Alpine:v3.23 | librewolf | 94.0-r0 | ALPINE-CVE-2021-38503 |
| Alpine:v3.24 | librewolf | 94.0-r0 | ALPINE-CVE-2021-38503 |
| Alpine:v3.20 | thunderbird | 91.3.2-r0 | ALPINE-CVE-2021-38503 |
| Alpine:v3.21 | thunderbird | 91.3.2-r0 | ALPINE-CVE-2021-38503 |
| Alpine:v3.22 | thunderbird | 91.3.2-r0 | ALPINE-CVE-2021-38503 |
| Alpine:v3.23 | thunderbird | 91.3.2-r0 | ALPINE-CVE-2021-38503 |
| Debian:12 | firefox-esr | 91.3.0esr-1 | DEBIAN-CVE-2021-38503 |
| Debian:13 | firefox-esr | 91.3.0esr-1 | DEBIAN-CVE-2021-38503 |
| Debian:14 | firefox-esr | 91.3.0esr-1 | DEBIAN-CVE-2021-38503 |
| Debian:12 | thunderbird | 1:91.3.0-1 | DEBIAN-CVE-2021-38503 |
| Debian:13 | thunderbird | 1:91.3.0-1 | DEBIAN-CVE-2021-38503 |
| Debian:14 | thunderbird | 1:91.3.0-1 | DEBIAN-CVE-2021-38503 |
| Rocky Linux:8 | firefox | 0:91.3.0-1.el8 | RLSA-2021:4123 |
| Rocky Linux:8 | thunderbird | 0:91.3.0-2.el8 | RLSA-2021:4130 |
| Rocky Linux:8 | thunderbird | 0:91.3.0-2.el8_4 | RLSA-2021:4130 |
| Ubuntu:22.04:LTS | firefox | 94.0+build3-0ubuntu1 | UBUNTU-CVE-2021-38503 |
| Ubuntu:22.04:LTS | mozjs78 | no fix listed | UBUNTU-CVE-2021-38503 |
| Ubuntu:22.04:LTS | thunderbird | 1:91.3.1+build1-0ubuntu1 | UBUNTU-CVE-2021-38503 |
Affected products (as reported)
| Vendor | Product | Versions |
|---|---|---|
| Mozilla | Firefox | unspecified – before 94 |
| Mozilla | Thunderbird | unspecified – before 91.3 |
| Mozilla | Firefox ESR | unspecified – before 91.3 |
References
- https://www.mozilla.org/security/advisories/mfsa2021-49/ x_refsource_MISC
- https://www.mozilla.org/security/advisories/mfsa2021-50/ x_refsource_MISC
- https://www.mozilla.org/security/advisories/mfsa2021-48/ x_refsource_MISC
- https://bugzilla.mozilla.org/show_bug.cgi?id=1729517 x_refsource_MISC
- DSA-5026 vendor-advisory, x_refsource_DEBIAN
- [debian-lts-announce] 20211229 [SECURITY] [DLA 2863-1] firefox-esr security update mailing-list, x_refsource_MLIST
- DSA-5034 vendor-advisory, x_refsource_DEBIAN
- [debian-lts-announce] 20220104 [SECURITY] [DLA 2874-1] thunderbird security update mailing-list, x_refsource_MLIST
- GLSA-202202-03 vendor-advisory, x_refsource_GENTOO
- GLSA-202208-14 vendor-advisory, x_refsource_GENTOO