Stored XSS via case-sensitive HTML filtering
Published Sep 6, 2021 · Updated Aug 3, 2024
Stored XSS in BookStack before 21.08.2 allows remote authenticated users to execute script in another user's browser via crafted page HTML. The HtmlContentFilter::removeScripts method performs case-sensitive XPath substring checks, leaving mixed-case JavaScript and data URIs or event attributes intact. An editor-equivalent role must save malicious page content and a victim must render it, enabling browser-context data access or actions.
Summary
What happened
Stored XSS in BookStack before 21.08.2 allows remote authenticated users to execute script in another user's browser via crafted page HTML. The HtmlContentFilter::removeScripts method performs case-sensitive XPath substring checks, leaving mixed-case JavaScript and data URIs or event attributes intact. An editor-equivalent role must save malicious page content and a victim must render it, enabling browser-context data access or actions.
The record
- CVE
- CVE-2021-3768
- Published
- Sep 6, 2021
- Updated
- Aug 3, 2024
- Vendor
- BookStack
- Product
- BookStack
- Classifications
- CWE-79, T1059.007
- Attack vector
- network
- Privileges
- authenticated
Timeline
How it unfolded
- Sep 6, 2021CVE publishedPublication date reported by the CVE source.
- Aug 3, 2024Record updatedLatest update available in the CVE record.
Exploitability
Present is not the same as exploitable
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Is a vulnerable build present?
Compare these published version ranges with your installed build and any vendor patches.
- Affected versionversion=unspecified <21.08.2
What conditions does exploitation require?
What is affected?
Attacks
What attackers are doing with it
Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.
Weakness, pattern, technique
Public exploit references
- huntr stored-XSS bounty demonstrationproof of concept · unverified
Labels summarize the accepted research assessment. They do not indicate a test against your environment.
Technologies
Your stack
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Your stack
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