Go to homepageCyberStrike

Menu

Star on GitHub · 3.2k
Sign inDownload

CVE-2021-38503

10.0 · CRITICAL

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.

Published Dec 8, 2021CWE-863EPSS 4.12%

Overview

CVE-2021-38503 is a critical-severity vulnerability. It was published on December 8, 2021 and has a CVSS 3.1 base score of 10.0 (CRITICAL).

This vulnerability has a CVSS 3.1 base score of 10.0, rated CRITICAL. It can be exploited remotely over the network. No authentication or special privileges are required for exploitation.

Technical 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.

Remediation

Check the references section for vendor advisories, patches, and mitigation guidance. If immediate patching is not possible, review the CVSS vector to understand the attack surface and apply compensating controls such as network segmentation or access restrictions.

References

Refbugzilla.mozilla.org/show_bug.cgi?id=1729517Reflists.debian.org/debian-lts-announce/2021/12/msg00030.htmlReflists.debian.org/debian-lts-announce/2022/01/msg00001.htmlRefsecurity.gentoo.org/glsa/202202-03Refsecurity.gentoo.org/glsa/202208-14Refwww.debian.org/security/2021/dsa-5026Refwww.debian.org/security/2022/dsa-5034Refwww.mozilla.org/security/advisories/mfsa2021-48/Refwww.mozilla.org/security/advisories/mfsa2021-49/Refwww.mozilla.org/security/advisories/mfsa2021-50/

How CyberStrike helps

Frequently asked questions

What is CVE-2021-38503?

CVE-2021-38503 is a critical-severity vulnerability. It was published on December 8, 2021 and has a CVSS 3.1 base score of 10.0 (CRITICAL).

How severe is CVE-2021-38503?

This vulnerability has a CVSS 3.1 base score of 10.0, rated CRITICAL. It can be exploited remotely over the network. No authentication or special privileges are required for exploitation.

How do I fix or remediate CVE-2021-38503?

Check the references section for vendor advisories, patches, and mitigation guidance. If immediate patching is not possible, review the CVSS vector to understand the attack surface and apply compensating controls such as network segmentation or access restrictions.

How can CyberStrike help with CVE-2021-38503?

CyberStrike is an open-source, AI-augmented pentesting engine. Rather than flag a version number, it tests whether an issue like CVE-2021-38503 is actually reachable in your own applications and APIs, then verifies each finding before reporting it. That tells you if the weakness is a real, exploitable risk in your environment or a false positive you can safely deprioritize.

Related CRITICAL CVEs from 2021

View all
Browse by year2026202520242023202220212020201920182017201620152014201320122011201020092008200720062005200420032002200120001999