CVE-2020-6816 – bleach

Package

Manager: pip
Name: bleach
Vulnerable Version: >=0 <3.1.2

Severity

Level: Medium

CVSS v3.1: CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N

CVSS v4.0: CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:P/VC:N/VI:N/VA:N/SC:L/SI:L/SA:N

EPSS: 0.00366 pctl0.57809

Details

Bleach vulnerable to mutation XSS via whitelisted math or svg and raw tag ### Impact A [mutation XSS](https://cure53.de/fp170.pdf) affects users calling `bleach.clean` with all of: * the `svg` or `math` in the allowed/whitelisted tags * an RCDATA tag (see below) in the allowed/whitelisted tags * the keyword argument `strip=False` ### Patches Users are encouraged to upgrade to bleach v3.1.2 or greater. ### Workarounds * modify `bleach.clean` calls to use `strip=True`, or not whitelist `math` or `svg` tags and one or more of the following tags: ``` script noscript style noframes xmp noembed iframe ``` * A strong [Content-Security-Policy](https://developer.mozilla.org/en-US/docs/Web/HTTP/CSP) without `unsafe-inline` and `unsafe-eval` [`script-src`s](https://developer.mozilla.org/en-US/docs/Web/HTTP/Headers/Content-Security-Policy/script-src)) will also help mitigate the risk. ### References * https://bugzilla.mozilla.org/show_bug.cgi?id=1621692 * https://cure53.de/fp170.pdf * https://nvd.nist.gov/vuln/detail/CVE-2020-6816 * https://www.checkmarx.com/blog/vulnerabilities-discovered-in-mozilla-bleach ### Credits * Reported by [Yaniv Nizry](https://twitter.com/ynizry) from the CxSCA AppSec group at Checkmarx ### For more information If you have any questions or comments about this advisory: * Open an issue at [https://github.com/mozilla/bleach/issues](https://github.com/mozilla/bleach/issues) * Email us at [security@mozilla.org](mailto:security@mozilla.org)

Metadata

Created: 2020-03-24T15:06:32Z
Modified: 2024-09-12T20:49:31Z
Source: https://github.com/github/advisory-database/blob/main/advisories/github-reviewed/2020/03/GHSA-m6xf-fq7q-8743/GHSA-m6xf-fq7q-8743.json
CWE IDs: ["CWE-79"]
Alternative ID: GHSA-m6xf-fq7q-8743
Finding: F008
Auto approve: 1