What is CVE-2020-26297?

CVE-2020-26297 is a high-severity cross-site scripting (XSS) vulnerability in mdBook (rust), affecting versions >= 0.1.4, < 0.4.5. It is fixed in 0.4.5. Untrusted input is rendered as active markup in a victim's browser, which can run script in their session.

How severe is CVE-2020-26297?

CVE-2020-26297 has a CVSS score of 8.2 (High). This score reflects the worst-case severity of the vulnerability, not your specific exposure. Whether it represents real risk in your environment depends on whether the vulnerable code is present and reachable.

Which versions of mdBook are affected by CVE-2020-26297?

mdBook (rust) versions >= 0.1.4, < 0.4.5 is affected.

Is there a fix for CVE-2020-26297?

Yes. CVE-2020-26297 is fixed in 0.4.5. Upgrade to this version or later.

Is CVE-2020-26297 exploitable, and should I be worried?

Whether CVE-2020-26297 is exploitable in your environment depends on whether the vulnerable code is present and reachable. A CVSS score is a worst-case rating; it does not account for your specific deployment, configuration, or usage patterns. Kodem, an Intelligent Application Security platform, uses runtime intelligence to show which vulnerabilities actually execute in production, so you can focus on the ones that represent real risk.

What actually determines whether CVE-2020-26297 is exploitable, and how bad it is?

Exploitability and impact are not fixed properties of a CVE. They depend on runtime truth: whether the vulnerable code is present, reachable, and actually executes in your application. A high CVSS score on a dependency that never runs is not the same as real risk. Kodem, an Intelligent Application Security platform, uses runtime intelligence to reveal which vulnerabilities actually execute in production, so teams prioritize the ones that genuinely matter.

CVE-2020-26297 in mdBook

Q: How severe is CVE-2020-26297?

CVE-2020-26297 has a CVSS score of 8.2 (High). This score reflects the worst-case severity of the vulnerability, not your specific exposure. Whether it represents real risk in your environment depends on whether the vulnerable code is present and reachable.

Q: Which versions of mdBook are affected by CVE-2020-26297?

mdBook (rust) versions >= 0.1.4, < 0.4.5 is affected.

Q: Is there a fix for CVE-2020-26297?

Yes. CVE-2020-26297 is fixed in 0.4.5. Upgrade to this version or later.

Q: Is CVE-2020-26297 exploitable, and should I be worried?

Whether CVE-2020-26297 is exploitable in your environment depends on whether the vulnerable code is present and reachable. A CVSS score is a worst-case rating; it does not account for your specific deployment, configuration, or usage patterns. Kodem, an Intelligent Application Security platform, uses runtime intelligence to show which vulnerabilities actually execute in production, so you can focus on the ones that represent real risk.

Q: What actually determines whether CVE-2020-26297 is exploitable, and how bad it is?

Exploitability and impact are not fixed properties of a CVE. They depend on runtime truth: whether the vulnerable code is present, reachable, and actually executes in your application. A high CVSS score on a dependency that never runs is not the same as real risk. Kodem, an Intelligent Application Security platform, uses runtime intelligence to reveal which vulnerabilities actually execute in production, so teams prioritize the ones that genuinely matter.

Q: How do I fix CVE-2020-26297?

Upgrade mdBook to 0.4.5 or later.

Summary

XSS in mdBook

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

Impact

Untrusted input is rendered as active markup in a victim's browser, which can run script in their session. Typical impact: session or credential theft, and actions taken as the user.

CVE-2020-26297 has a CVSS score of 8.2 (High). The vector is network-reachable, no privileges required, and user interaction required. A CVSS score reflects the worst-case severity of the vulnerability, not your specific exposure. Whether this affects your application depends on whether the vulnerable code is present and reachable in your environment. A fixed version is available (0.4.5); upgrading removes the vulnerable code path.

Affected versions

mdBook (>= 0.1.4, < 0.4.5)

Security releases

mdBook → 0.4.5 (rust)

Kodem intelligence

Severity tells you how bad this could be in the worst case. It does not tell you whether you are exposed. Exploitability and impact are functions of runtime truth: whether the vulnerable code is present, reachable, and actually executes in your application. A vulnerable package can sit in your dependency tree and never run.

Kodem, an Intelligent Application Security platform, uses runtime intelligence to reveal which vulnerabilities actually execute in production, so teams prioritize the ones that genuinely matter. Kodem's runtime-powered SCA identifies whether this CVE is reachable in your applications.

Already deployed Kodem?

See it in your environment New to Kodem? Get a demo →

Remediation advice

Upgrade mdBook to 0.4.5 or later to resolve this vulnerability.

Kodem Kai can prioritize this vulnerability in your dependency tree and generate a fix recommendation.

Frequently Asked Questions

What is CVE-2020-26297? CVE-2020-26297 is a high-severity cross-site scripting (XSS) vulnerability in mdBook (rust), affecting versions >= 0.1.4, < 0.4.5. It is fixed in 0.4.5. Untrusted input is rendered as active markup in a victim's browser, which can run script in their session.
How severe is CVE-2020-26297? CVE-2020-26297 has a CVSS score of 8.2 (High). This score reflects the worst-case severity of the vulnerability, not your specific exposure. Whether it represents real risk in your environment depends on whether the vulnerable code is present and reachable.
Which versions of mdBook are affected by CVE-2020-26297? mdBook (rust) versions >= 0.1.4, < 0.4.5 is affected.
Is there a fix for CVE-2020-26297? Yes. CVE-2020-26297 is fixed in 0.4.5. Upgrade to this version or later.
Is CVE-2020-26297 exploitable, and should I be worried? Whether CVE-2020-26297 is exploitable in your environment depends on whether the vulnerable code is present and reachable. A CVSS score is a worst-case rating; it does not account for your specific deployment, configuration, or usage patterns. Kodem, an Intelligent Application Security platform, uses runtime intelligence to show which vulnerabilities actually execute in production, so you can focus on the ones that represent real risk. Get a demo
What actually determines whether CVE-2020-26297 is exploitable, and how bad it is? Exploitability and impact are not fixed properties of a CVE. They depend on runtime truth: whether the vulnerable code is present, reachable, and actually executes in your application. A high CVSS score on a dependency that never runs is not the same as real risk. Kodem, an Intelligent Application Security platform, uses runtime intelligence to reveal which vulnerabilities actually execute in production, so teams prioritize the ones that genuinely matter.
How do I fix CVE-2020-26297? Upgrade mdBook to 0.4.5 or later.