Cross-site scripting via unchecked end-tag namespace
Published May 22, 2026 · Updated May 22, 2026
Cross-site scripting in Go golang.org/x/net/html before 0.55.0 allows remote attackers to execute script via parsed and rendered HTML. In the parser's “in body” insertion mode, the “any other end tag” path matches a start tag without verifying that it belongs to the HTML namespace. Exploitation requires an application to parse attacker-controlled HTML, sanitize the resulting tree, and render it for a user, whose browser then executes the injected script.
Summary
What happened
Cross-site scripting in Go golang.org/x/net/html before 0.55.0 allows remote attackers to execute script via parsed and rendered HTML. In the parser's “in body” insertion mode, the “any other end tag” path matches a start tag without verifying that it belongs to the HTML namespace. Exploitation requires an application to parse attacker-controlled HTML, sanitize the resulting tree, and render it for a user, whose browser then executes the injected script.
The record
- CVE
- CVE-2026-42506
- Published
- May 22, 2026
- Updated
- May 22, 2026
- Vendor
- Go
- Product
- golang.org/x/net/html
- Classifications
- CWE-79, T1189
- Attack vector
- network
- Privileges
- unauthenticated
Timeline
How it unfolded
- May 22, 2026CVE publishedPublication date reported by the CVE source.
- May 22, 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=0 <0.55.0
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
No public exploit references are available in this record.
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Technologies
Your stack
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Your stack
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