Service interruption via repeated GB18030 table scans
Published Apr 10, 2026 · Updated Apr 10, 2026
Algorithmic complexity in musl libc 1.2.0 through 1.2.6 allows attackers to hang processes decoding crafted GB18030 input. The GB18030 four-byte path in iconv.c repeatedly scans the 23,940-entry gb18030126 table inside an input-dependent gap-skipping loop. Reachability requires a process to pass attacker-controlled data or an attacker-controlled encoding declaration to iconv(); one four-byte character can trigger about 500 million comparisons and exhaust CPU.
Summary
What happened
Algorithmic complexity in musl libc 1.2.0 through 1.2.6 allows attackers to hang processes decoding crafted GB18030 input. The GB18030 four-byte path in iconv.c repeatedly scans the 23,940-entry gb18030126 table inside an input-dependent gap-skipping loop. Reachability requires a process to pass attacker-controlled data or an attacker-controlled encoding declaration to iconv(); one four-byte character can trigger about 500 million comparisons and exhaust CPU.
The record
- CVE
- CVE-2026-6042
- Published
- Apr 10, 2026
- Updated
- Apr 10, 2026
- Vendor
- musl
- Product
- musl libc
- Classifications
- CWE-407, CWE-404, T1499.004
- Attack vector
- local
- Privileges
- authenticated
Timeline
How it unfolded
- Apr 10, 2026CVE publishedPublication date reported by the CVE source.
- Apr 10, 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=1.2.0
- Affected versionversion=1.2.1
- Affected versionversion=1.2.2
- Affected versionversion=1.2.3
- Affected versionversion=1.2.4
- Affected versionversion=1.2.5
- Affected versionversion=1.2.6
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
- Crafted GB18030 character CPU-exhaustion 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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