CVE-2026-5089

Status: DeferredHigh (7.3)—

YAML::Syck versions before 1.38 for Perl has an out-of-bounds read.

The base60 (sexagesimal) parsing code in perl_syck.h has a buffer underflow bug in both int#base60 and float#base60 handlers. When processing the leftmost segment of a colon-separated value (e.g., the 1 in 1:30:45), the inner while loop can decrement a pointer past the start of the string buffer:

When no colon is found (final/leftmost segment), colon becomes ptr-1, and the subsequent *colon dereference reads one byte before the allocated buffer.

Technical details traces, logs and code from the original report

    while ( colon >= ptr && *colon != ':' )
    {
        colon--;
    }
    if ( *colon == ':' ) *colon = '\0';  // colon may be ptr-1 here

CVSS

Version: 3.1
Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:L/A:L
Base score: 7.3

Exploitation probability (EPSS)

Probability of exploitation in the next 30 days: 0.42%
Percentile among all scored CVEs: 34
Score date: 10/5/2026

EPSS (Exploit Prediction Scoring System, FIRST) estimates how likely a vulnerability is to be exploited in the wild within 30 days. It complements CVSS (impact) and CISA KEV (confirmed exploitation).

🎯 ATT&CK techniques

How this vulnerability is exploited and what the attacker gains, in MITRE ATT&CK terms.

ExploitationT1190 Exploit Public-Facing Applicationinitial access85 %
Primary impactT1005 Data from Local Systemcollection70 %

Acceso remoto sin autenticación (AV:N, PR:N, UI:N) en parser YAML de aplicaciones Perl. Buffer underflow permite lectura de memoria adyacente.

Inferred by our analysis agent from the official description, CVSS vector and CWE, and checked by a supervisor. May contain errors.

🛡️ ATT&CK mitigations that cover these techniques

Vulnerability Scanning Privileged Account Management Network Segmentation Limit Access to Resource Over Network Filter Network Traffic Application Isolation and Sandboxing

Affected technologies (1)

⚠ AI-inferred from the description — NVD hasn't analyzed this CVE yet, these aren't verified CPEs.

Yaml Syck — Yaml-syck^AI

CWEs

CWE-124

References

Raw JSON (NVD)

Show

{
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  "published": "2026-05-12T17:16:21.720",
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  "descriptions": [
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      "lang": "en",
      "value": "YAML::Syck versions before 1.38 for Perl  has an out-of-bounds read.\n\nThe base60 (sexagesimal) parsing code in perl_syck.h has a buffer underflow bug in both int#base60 and float#base60 handlers. When processing the leftmost segment of a colon-separated value (e.g., the 1 in 1:30:45), the inner while loop can decrement a pointer past the start of the string buffer:\n\n    while ( colon >= ptr && *colon != ':' )\n    {\n        colon--;\n    }\n    if ( *colon == ':' ) *colon = '\\0';  // colon may be ptr-1 here\n\nWhen no colon is found (final/leftmost segment), colon becomes ptr-1, and the subsequent *colon dereference reads one byte before the allocated buffer."
    }
  ],
  "lastModified": "2026-06-17T10:58:25.620",
  "sourceIdentifier": "9b29abf9-4ab0-4765-b253-1875cd9b441e"
}