Cross-site scripting via named whitespace URI bypass
Published Aug 12, 2026 · Updated Aug 12, 2026
Cross-site scripting in Loofah 2.25.0 through 2.25.1 allows attackers to inject script through crafted browser-bound URLs. The allowed_uri? helper uses CGI.unescapeHTML, which leaves and intact, so the scheme check accepts an encoded javascript: URI that browsers normalize and execute. Exploitation requires a caller to pass an HTML-encoded, user-controlled URL directly to the helper and render the accepted value; the default sanitize() path is unaffected.
Summary
What happened
Cross-site scripting in Loofah 2.25.0 through 2.25.1 allows attackers to inject script through crafted browser-bound URLs. The allowed_uri? helper uses CGI.unescapeHTML, which leaves and intact, so the scheme check accepts an encoded javascript: URI that browsers normalize and execute. Exploitation requires a caller to pass an HTML-encoded, user-controlled URL directly to the helper and render the accepted value; the default sanitize() path is unaffected.
The record
- CVE
- CVE-2026-73491
- Published
- Aug 12, 2026
- Updated
- Aug 12, 2026
- Vendor
- flavorjones
- Product
- Loofah
- Classifications
- CWE-184, T1203
- Attack vector
- network
- Privileges
- authenticated
Timeline
How it unfolded
- Aug 12, 2026CVE publishedPublication date reported by the CVE source.
- Aug 12, 2026Record 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=>= 2.25.0, < 2.25.2
What conditions does exploitation require?
What is affected?
Published CVSS scores
CVSS describes severity. EPSS estimates exploitation probability.
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
- GHSA named-whitespace JavaScript URI demonstrationproof of concept · demonstrated
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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