Description
css_parser is a Ruby CSS parser. Prior to 2.1.0 and 1.22.0, the CSS Parser gem does not validate HTTPS connections, allowing a Man-in-the-Middle (MITM) attacker to inject or modify CSS content when stylesheets are loaded via HTTPS. The connection is established with OpenSSL::SSL::VERIFY_NONE, meaning any HTTPS certificate—even entirely untrusted—will be accepted without validation. This vulnerability is fixed in 2.1.0 and 1.22.0.
Affected products
| Vendor | Product | Affected | Fixed |
|---|---|---|---|
| premailer | css_parser | >= 2.0.0, < 2.1.0, < 1.22.0 | — |
Fixed in Linux distributions
Distributions backport fixes, so the version that fixes this vulnerability differs per release — upgrade to at least the version shown. From the distributions' security trackers and advisories.
Debian
Security tracker ↗| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| Debian 14 | ruby-css-parser | 2.1.0-1 | — |
| Debian 13 | ruby-css-parser | 1.19.0-1+deb13u1 | — |
| Debian 12 | ruby-css-parser | 1.6.0-2+deb12u1 | — |
Ubuntu
Security tracker ↗| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| Ubuntu 26.10 | ruby-css-parser | No fix yet | — |
| Ubuntu 26.04 LTS | ruby-css-parser | No fix yet | — |
| Ubuntu 25.10 | ruby-css-parser | No fix yet | — |
| Ubuntu 24.04 LTS | ruby-css-parser | No fix yet | — |
| Ubuntu 22.04 LTS | ruby-css-parser | No fix yet | — |
Show 3 more (older releases, extended support, other products)Fewer releases
| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| Ubuntu 20.04 LTS | ruby-css-parser | No fix yet | — |
| Ubuntu 18.04 LTS | ruby-css-parser | No fix yet | — |
| Ubuntu 16.04 LTS | ruby-css-parser | No fix yet | — |
Affected packages
| Ecosystem | Package | Affected | Fixed | Record |
|---|---|---|---|---|
| RubyGems | css_parser | >= 2.0.0, < 2.1.0 | 2.1.0 | GHSA-ff6c-w6qf-7xqc |
| RubyGems | css_parser | < 1.22.0 | 1.22.0 | GHSA-ff6c-w6qf-7xqc |
References
- https://github.com/premailer/css_parser/security/advisories/GHSA-ff6c-w6qf-7xqc
- https://github.com/premailer/css_parser/issues/185
- https://github.com/premailer/css_parser/commit/35e689c904225add78e0c488cf04bad052666449
- https://github.com/premailer/css_parser/commit/e0c95d5abe91b237becb90ff316531a6547ada18