CVE-2010-2939 in OpenSSL
Summary
by MITRE
Double free vulnerability in the ssl3_get_key_exchange function in the OpenSSL client (ssl/s3_clnt.c) in OpenSSL 1.0.0a, 0.9.8, 0.9.7, and possibly other versions, when using ECDH, allows context-dependent attackers to cause a denial of service (crash) and possibly execute arbitrary code via a crafted private key with an invalid prime. NOTE: some sources refer to this as a use-after-free issue.
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Analysis
by VulDB Data Team • 11/10/2024
The vulnerability identified as CVE-2010-2939 represents a critical double free condition within the OpenSSL cryptographic library that affects multiple versions including 1.0.0a, 0.9.8, and 0.9.7. This flaw exists specifically within the ssl3_get_key_exchange function located in the ssl/s3_clnt.c file, which is responsible for handling key exchange operations during SSL/TLS handshake processes. The vulnerability manifests when the OpenSSL client processes ECDH (Elliptic Curve Diffie-Hellman) key exchanges, making it particularly dangerous for systems that rely on elliptic curve cryptography for secure communications. The issue is classified under CWE-415 as a double free vulnerability, which occurs when the same memory block is freed twice, potentially leading to memory corruption and unpredictable behavior in the affected application.
The technical exploitation of this vulnerability requires an attacker to craft a malicious private key containing an invalid prime number that triggers the double free condition during the SSL/TLS handshake process. When the OpenSSL client encounters such a malformed key during ECDH key exchange operations, the ssl3_get_key_exchange function attempts to free memory resources twice, creating a scenario where the memory management system becomes corrupted. This memory corruption can result in program crashes, denial of service conditions, or potentially more severe consequences including arbitrary code execution depending on the specific system configuration and memory layout. The vulnerability is context-dependent, meaning that successful exploitation requires specific conditions to be met during the SSL/TLS connection establishment phase, particularly when ECDH cipher suites are negotiated.
The operational impact of CVE-2010-2939 extends beyond simple denial of service to potentially enable remote code execution in certain environments, making it a significant threat to network security infrastructure. Systems that use OpenSSL for SSL/TLS services and are configured to accept ECDH key exchanges become vulnerable to this attack vector. The vulnerability affects a wide range of applications and services that rely on OpenSSL, including web servers, email servers, VPN systems, and any other network services that implement SSL/TLS encryption. From an adversarial perspective, this vulnerability aligns with ATT&CK technique T1059.007 for command and scripting interpreter usage and T1499.004 for network denial of service, as it enables both service disruption and potential code execution. The double free condition creates an opportunity for attackers to manipulate memory structures, potentially allowing for privilege escalation or complete system compromise depending on the target environment and execution context.
Mitigation strategies for CVE-2010-2939 primarily focus on immediate software updates and patches from OpenSSL maintainers, as the vulnerability was addressed in subsequent releases of the OpenSSL library. Organizations should prioritize upgrading to OpenSSL versions 1.0.0b or later, or 0.9.8l and later, which contain the necessary fixes to prevent the double free condition during ECDH key exchange operations. Additionally, system administrators should consider disabling ECDH cipher suites if they are not essential for operations, as this provides an immediate workaround to prevent exploitation. Network monitoring should be enhanced to detect unusual SSL/TLS handshake behaviors that might indicate attempted exploitation of this vulnerability. The fix implemented by OpenSSL involves proper memory management checks within the ssl3_get_key_exchange function to ensure that memory blocks are only freed once, preventing the double free condition that leads to memory corruption and potential arbitrary code execution. Security teams should also conduct thorough vulnerability assessments to identify systems that may be running affected OpenSSL versions and ensure proper patch management procedures are in place to maintain system security.