Vulnerability record · CVE-2015-1789 · published 12 June 2015
CVE-2015-1789: OpenSSL X509_cmp_time out-of-bounds read causes denial of service
OOpenssl · Openssl
OpenSSL's X509_cmp_time function in crypto/x509/x509_vfy.c fails to properly validate a length field in ASN1_TIME data, leading to an out-of-bounds read and application crash. This affects OpenSSL before 0.9.8zg, 1.0.0 before 1.0.0s, 1.0.1 before 1.0.1n, and 1.0.2 before 1.0.2b. The flaw matters because it can be triggered remotely against servers that support client authentication with a custom verification callback.
Description
The X509_cmp_time function in crypto/x509/x509_vfy.c in OpenSSL before 0.9.8zg, 1.0.0 before 1.0.0s, 1.0.1 before 1.0.1n, and 1.0.2 before 1.0.2b allows remote attackers to cause a denial of service (out-of-bounds read and application crash) via a crafted length field in ASN1_TIME data, as demonstrated by an attack against a server that supports client authentication with a custom verification callback.
CVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
Automated analysis
high priorityCVSS 3.0 score is 7.5 (HIGH) with network reachability and no authentication, and EPSS is very high at 0.74483, though the flaw is limited to denial of service.
What it is
OpenSSL's X509_cmp_time function in crypto/x509/x509_vfy.c fails to properly validate a length field in ASN1_TIME data, leading to an out-of-bounds read and application crash. This affects OpenSSL before 0.9.8zg, 1.0.0 before 1.0.0s, 1.0.1 before 1.0.1n, and 1.0.2 before 1.0.2b. The flaw matters because it can be triggered remotely against servers that support client authentication with a custom verification callback.
Impact
A remote attacker can crash the application, causing a denial of service. There is no evidence of data confidentiality or integrity impact; the CVSS vector shows availability impact only.
Attack surface
The vulnerability is reachable over the network (AV:N) with no privileges or user interaction required (PR:N, UI:N). It is specifically demonstrated against a server that supports client authentication with a custom verification callback, meaning the attacker must be able to supply a crafted certificate during a TLS handshake.
Exploitation
The CVE is not listed in CISA KEV and no ransomware groups are documented using it. EPSS probability is 0.74483 (99.469th percentile), indicating a high likelihood of exploitation activity, but the reference tags do not include exploit or proof-of-concept labels.
What to do
- Upgrade OpenSSL to 0.9.8zg, 1.0.0s, 1.0.1n, 1.0.2b or later as applicable.
- Apply vendor patches for Oracle SPARC OPL service processor and any other affected products.
- Disable client authentication with custom verification callbacks where not strictly required.
- Monitor for and restrict untrusted client certificates if client authentication must remain enabled.
Detection
- Monitor application logs for crashes or abnormal termination in processes using OpenSSL during TLS handshakes with client authentication.
- Use network detection to flag malformed ASN1_TIME fields in client certificates presented during TLS handshakes.
- Track OpenSSL versions in use and alert on any instance older than the fixed releases.
This assessment is produced automatically and is not human-reviewed. Verify against the vendor advisory before acting on it.
Affected products
2 vulnerable configurations from NVD's CPE data, grouped by vendor and product.
References
Track CVE-2015-1789 inside VULONE
Watch it alongside the ransomware crews, C2 infrastructure and forum chatter that reference it, query it through the API and pull it into your SIEM over TAXII.
Related vulnerabilities
Same products first, then exploited flaws of the same weakness class.
Source: NIST National Vulnerability Database (record CVE-2015-1789), CISA KEV, FIRST EPSS (scores of 2026-09-26). This page is refreshed as NVD updates the record.
