Out-of-bounds read via sexagesimal parser pointer underflow
Published May 12, 2026 · Updated May 12, 2026
Out-of-bounds read in YAML::Syck before 1.38 allows attackers to trigger a one-byte read before a buffer via crafted sexagesimal YAML values. The int#base60 and float#base60 handlers in perl_syck.h decrement a colon pointer past the input-buffer start, then dereference it when the leftmost segment contains no colon. This requires YAML::Syck::ImplicitTyping to be enabled; the resulting undefined behavior includes process crashes or parsed-data corruption, while the published proof of concept usually returns the correct value.
Summary
What happened
Out-of-bounds read in YAML::Syck before 1.38 allows attackers to trigger a one-byte read before a buffer via crafted sexagesimal YAML values. The int#base60 and float#base60 handlers in perl_syck.h decrement a colon pointer past the input-buffer start, then dereference it when the leftmost segment contains no colon. This requires YAML::Syck::ImplicitTyping to be enabled; the resulting undefined behavior includes process crashes or parsed-data corruption, while the published proof of concept usually returns the correct value.
The record
- CVE
- CVE-2026-5089
- Published
- May 12, 2026
- Updated
- May 12, 2026
- Vendor
- Todd Rinaldo
- Product
- YAML::Syck
- Classifications
- CWE-124, T1499.004
- Attack vector
- network
- Privileges
- unauthenticated
Timeline
How it unfolded
- May 12, 2026CVE publishedPublication date reported by the CVE source.
- May 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=0 <1.38
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
- YAML::Syck issue 132 reproductionproof of concept · demonstrated
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Technologies
Your stack
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Your stack
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