CVE-2021-29272 Cross-site scripting in bluemonday
An attacker can bypass XSS protections in the bluemonday Go library by using uppercase Cyrillic characters to inject scripts.
- 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-2021-29272?
CVE-2021-29272 is a medium-severity cross-site scripting vulnerability in n/a, published on 27 Mar 2021. 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
bluemonday before 1.0.5 allows XSS because certain Go lowercasing converts an uppercase Cyrillic character, defeating a protection mechanism against the "script" string.
Weakness: CWE-79
Which versions are affected by CVE-2021-29272?
3 open source packages ship an affected version, including github.com/microcosm-cc/bluemonday. It affects 1 product.
| Package | Affected | Fixed in |
|---|---|---|
github.com/microcosm-cc/bluemonday Go | All versions | 1.0.5 |
github.com/microcosm-cc/bluemonday Go | All versions | 1.0.5 |
github.com/microcosm-cc/bluemonday Go | All versions | 1.0.5 |
Products include Microco Bluemonday.
How do I fix CVE-2021-29272?
Upgrade github.com/microcosm-cc/bluemonday to 1.0.5 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-2021-29272 being exploited?
There is no known exploitation of CVE-2021-29272 in the wild and no public exploit code.
Other vulnerabilities in n/a
Sources
Also known as CLEANSTART-2025-ZP95072, GHSA-3x58-xr87-2fcj, GO-2022-0762, UBUNTU-CVE-2021-29272.