Service hang via zero-length invalid-character advance
Published Jul 21, 2026 · Updated Jul 21, 2026
Infinite looping in Go Project x/text/unicode/norm before 0.39.0 allows remote attackers to hang applications via invalid UTF-8 input. The nextComposed function advances its input by a character size that compInfo reports as zero for invalid characters, so the loop never consumes the offending byte. Exposure requires an application to pass attacker-controlled malformed UTF-8 into affected normalization APIs; the bounded result is an application hang.
Summary
What happened
Infinite looping in Go Project x/text/unicode/norm before 0.39.0 allows remote attackers to hang applications via invalid UTF-8 input. The nextComposed function advances its input by a character size that compInfo reports as zero for invalid characters, so the loop never consumes the offending byte. Exposure requires an application to pass attacker-controlled malformed UTF-8 into affected normalization APIs; the bounded result is an application hang.
The record
- CVE
- CVE-2026-56852
- Published
- Jul 21, 2026
- Updated
- Jul 21, 2026
- Vendor
- The Go Project
- Product
- golang.org/x/text/unicode/norm
- Classifications
- CWE-835, T1499
- Attack vector
- network
- Privileges
- unauthenticated
Timeline
How it unfolded
- Jul 21, 2026CVE publishedPublication date reported by the CVE source.
- Jul 21, 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 <0.39.0
What conditions does exploitation require?
What is affected?
Published CVSS scores
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Attacks
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Weakness, pattern, technique
Public exploit references
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Technologies
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Your stack
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