GHSA-gx5w-rrhp-f436 is a high-severity (CVSS 8.2) Cross-site Scripting (XSS) vulnerability in mdBook. A fix is available for mdBook — see the affected versions and patch details below.
EPSS Exploitation Probability
Probability of exploitation in the next 30 days, from FIRST.org EPSS.
How urgent is this, really
GHSA-gx5w-rrhp-f436 by exploitation likelihood (EPSS) against impact (CVSS). Outside the shaded patch-first corner.
Where this sits among everything scored
Of 385,738 CVEs with a current EPSS score, this one falls in the < 10% band (highlighted). Counts from FIRST.org, log-scaled.
Real-World Exposure
mdBookReal-time download stats are indexed for npm and PyPI packages. This vulnerability affects crates.io packages — download data is not available via public APIs for these ecosystems.
Description
This is a cross-post of the official security advisory. The official post contains a signed version with our PGP key, as well.
The Rust Security Response Working Group was recently notified of a security issue affecting the search feature of mdBook, which could allow an attacker to execute arbitrary JavaScript code on the page.
The CVE for this vulnerability is CVE-2020-26297.
Overview
The search feature of mdBook (introduced in version 0.1.4) was affected by a cross site scripting vulnerability that allowed an attacker to execute arbitrary JavaScript code on an user's browser by tricking the user into typing a malicious search query, or tricking the user into clicking a link to the search page with the malicious search query prefilled.
mdBook 0.4.5 fixes the vulnerability by properly escaping the search query.
Mitigations
Owners of websites built with mdBook have to upgrade to mdBook 0.4.5 or greater and rebuild their website contents with it. It's possible to install mdBook 0.4.5 on the local system with:
cargo install mdbook --version 0.4.5 --force
Acknowledgements
Thanks to Kamil Vavra for responsibly disclosing the vulnerability to us according to our security policy.
Timeline of events
All times are listed in UTC.
- 2020-12-30 20:14 - The issue is reported to the Rust Security Response WG
- 2020-12-30 20:32 - The issue is acknowledged and the investigation began
- 2020-12-30 21:21 - Found the cause of the vulnerability and prepared the patch
- 2021-01-04 15:00 - Patched version released and vulnerability disclosed
Affected Packages
| Ecosystem | Package | Vulnerable range | Fix |
|---|---|---|---|
| 🦀crates.io | mdBook | ≥ 0.1.4&&< 0.4.5 | 0.4.5cargo update -p mdBook --precise 0.4.5 |
Affected Products
mdbookrust-langDetection & mitigation playbook
Open-source dependencyDetect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for mdBook, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.
Fix
Update mdBook to 0.4.5 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms GHSA-gx5w-rrhp-f436 is resolved across your whole dependency graph.
Workarounds
Escape or sanitise the affected output on the server side rather than relying on client-side filtering, and add a Content-Security-Policy that blocks inline script execution so injected markup cannot run even if it reaches the page.
Frequently Asked Questions
Is GHSA-gx5w-rrhp-f436 in your dependencies?
Find it across crates.io, including transitive dependencies.