CVE-2021-23980 Cross-site scripting in Bleach
Mutation XSS in Bleach allows code execution when specific non-default tags and settings are used for HTML sanitization.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Over the internet
- Victim action needed
- A user has to click or open something
- Fix
- Available
What is CVE-2021-23980?
CVE-2021-23980 is a medium-severity cross-site scripting vulnerability in Mozilla Bleach, published on 16 Feb 2023. An attacker can exploit it over the internet without logging in, and only if a user opens a file or follows a link.
Official description
A mutation XSS affects users calling bleach.clean with all of: svg or math in the allowed tags p or br in allowed tags style, title, noscript, script, textarea, noframes, iframe, or xmp in allowed tags the keyword argument strip_comments=False Note: none of the above tags are in the default allowed tags and strip_comments defaults to True.
Weakness: CWE-79
Which versions are affected by CVE-2021-23980?
3 open source packages ship an affected version, including bleach. It affects 1 product.
| Package | Affected | Fixed in |
|---|---|---|
bleach PyPI | All versions | 3.3.0 |
bleach PyPI | All versions | 3.3.0 |
bleach PyPI | All versions | 3.3.0 |
Products include Mozilla Bleach.
How do I fix CVE-2021-23980?
Upgrade bleach to 3.3.0 or later.
Escape output for the context it lands in and set a strict Content Security Policy. Upgrading the affected component is the real fix. More about Cross-site scripting.
Is CVE-2021-23980 being exploited?
It is not confirmed as exploited in the wild, but public exploit code for CVE-2021-23980 exists.
Other vulnerabilities in Mozilla Bleach
Sources
Also known as DEBIAN-CVE-2021-23980, DLA-2620-1, DSA-4892-1, GHSA-vv2x-vrpj-qqpq, MGASA-2021-0260, OESA-2022-1861 and 2 more.