CVE-2010-0740 in OpenSSL
Summary
by MITRE
The ssl3_get_record function in ssl/s3_pkt.c in OpenSSL 0.9.8f through 0.9.8m allows remote attackers to cause a denial of service (crash) via a malformed record in a TLS connection that triggers a NULL pointer dereference, related to the minor version number. NOTE: some of these details are obtained from third party information.
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Analysis
by VulDB Data Team • 05/03/2026
The vulnerability identified as CVE-2010-0740 represents a critical denial of service flaw within the OpenSSL cryptographic library that affects versions 0.9.8f through 0.9.8m. This issue resides in the ssl3_get_record function located in the ssl/s3_pkt.c source file, which handles the processing of TLS protocol records during secure communications. The vulnerability manifests when a remote attacker crafts a malformed TLS record that contains an invalid minor version number, causing the affected OpenSSL implementation to crash during the record processing phase.
The technical root cause of this vulnerability stems from inadequate input validation within the SSL/TLS record parsing mechanism. When OpenSSL encounters a TLS record with an unexpected or malformed minor version number, the ssl3_get_record function fails to properly handle this edge case, leading to a NULL pointer dereference condition. This occurs because the function attempts to access memory through a pointer that has not been properly initialized or validated, resulting in an immediate crash of the application or service using the vulnerable OpenSSL library. The vulnerability specifically targets the protocol version negotiation process where the minor version number is checked against expected values, but insufficient validation allows malformed data to propagate through the system.
The operational impact of this vulnerability extends beyond simple service disruption as it can be exploited by remote attackers to perform targeted denial of service attacks against systems running vulnerable OpenSSL versions. Any service that relies on OpenSSL for TLS/SSL encryption, including web servers, email servers, database servers, and other network services, becomes vulnerable to this attack vector. The crash occurs during the initial handshake phase of TLS connections, making it particularly effective as a DoS attack since it can prevent legitimate users from establishing secure connections to affected services. This vulnerability is especially concerning in high-availability environments where maintaining continuous service availability is critical for business operations.
Mitigation strategies for CVE-2010-0740 primarily focus on immediate software updates and patches provided by OpenSSL maintainers. Organizations should prioritize upgrading to OpenSSL versions 0.9.8n or later, which contain the necessary fixes to properly validate TLS record minor version numbers and prevent the NULL pointer dereference condition. Additionally, network-level mitigations can include implementing firewall rules to restrict TLS connection attempts from suspicious sources or deploying intrusion detection systems that can identify malformed TLS records. From a security framework perspective, this vulnerability aligns with CWE-476 which describes NULL pointer dereference conditions, and it maps to ATT&CK technique T1499.004 related to network denial of service attacks. System administrators should also consider implementing redundant services and failover mechanisms to minimize the impact of successful exploitation attempts, while monitoring for unusual connection patterns that might indicate active exploitation of this vulnerability.