Is CVE-2013-6420 in the CISA KEV catalog?

No. CVE-2013-6420 is not currently on the CISA Known Exploited Vulnerabilities list.

What is the CVSS severity of CVE-2013-6420?

CVE-2013-6420 has a CVSS v2 base score of 7.5 (HIGH).

What is the EPSS score for CVE-2013-6420?

CVE-2013-6420 has an EPSS score of 34.83% (98th percentile), estimating the probability of exploitation in the next 30 days.

CVE & CISA-KEV Catalog

CVE-2013-6420

HIGHEPSS 98th pctl

7.5

CVSS v2

NVD

Description

The asn1_time_to_time_t function in ext/openssl/openssl.c in PHP before 5.3.28, 5.4.x before 5.4.23, and 5.5.x before 5.5.7 does not properly parse (1) notBefore and (2) notAfter timestamps in X.509 certificates, which allows remote attackers to execute arbitrary code or cause a denial of service (memory corruption) via a crafted certificate that is not properly handled by the openssl_x509_parse function.

CWE-119Buffer Overflow

CVSS v2 Vector

No CVSS vector data available.

Exploit Intelligence

34.83%probability of exploitation in 30 days

98thpercentile

Very high risk: more likely to be exploited than 98% of all known CVEs.

References

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This product uses NVD data but is not endorsed or certified by the NVD. EPSS scores courtesy of FIRST.org (https://www.first.org/epss). Source: CISA KEV Catalog. Data as of 2026-04-29.