CVE-2012-2333 in OpenSSL
Summary
by MITRE
Integer underflow in OpenSSL before 0.9.8x, 1.0.0 before 1.0.0j, and 1.0.1 before 1.0.1c, when TLS 1.1, TLS 1.2, or DTLS is used with CBC encryption, allows remote attackers to cause a denial of service (buffer over-read) or possibly have unspecified other impact via a crafted TLS packet that is not properly handled during a certain explicit IV calculation.
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Analysis
by VulDB Data Team • 12/23/2024
The vulnerability identified as CVE-2012-2333 represents a critical integer underflow condition within OpenSSL implementations that affects multiple versions including 0.9.8x series, 1.0.0j and earlier, and 1.0.1c and earlier releases. This flaw specifically manifests when TLS 1.1, TLS 1.2, or DTLS protocols are employed alongside CBC (Cipher Block Chaining) encryption mechanisms. The vulnerability stems from improper handling of explicit IV (Initialization Vector) calculations during TLS packet processing, creating a scenario where integer arithmetic operations result in underflow conditions that can lead to unpredictable system behavior. The issue is particularly dangerous because it affects fundamental cryptographic communication protocols that are widely deployed across internet infrastructure, making it a prime target for exploitation by malicious actors seeking to disrupt services or potentially gain unauthorized access to systems.
The technical implementation of this vulnerability involves a specific flaw in the TLS protocol handling logic where an integer underflow occurs during the calculation of explicit IV values for CBC encryption modes. When a maliciously crafted TLS packet is received, the OpenSSL implementation fails to properly validate the integer values used in the IV calculation process, leading to an underflow condition that can cause buffer over-reads or other memory corruption issues. This condition specifically impacts the way OpenSSL processes TLS records when using CBC encryption, where explicit IV values are generated and used for each encrypted block. The integer underflow creates a scenario where calculated values become negative or exceed expected ranges, potentially causing memory access violations or unpredictable behavior in the cryptographic processing stack. This flaw operates at the protocol level and can be triggered through network-based attacks without requiring authentication or privileged access.
The operational impact of CVE-2012-2333 extends beyond simple denial of service conditions to potentially enable more sophisticated attacks depending on the target system's configuration and implementation. Remote attackers can exploit this vulnerability to cause system crashes or restarts through buffer over-read conditions, effectively creating persistent denial of service scenarios that can severely impact availability of critical services. In some configurations, the integer underflow may also enable attackers to manipulate memory contents or potentially execute arbitrary code, though this requires additional conditions and is less common than the denial of service impact. The vulnerability affects a wide range of systems including web servers, email servers, database servers, and any network service that relies on OpenSSL for secure communications. Organizations running affected versions of OpenSSL face significant risk as the vulnerability can be exploited by anyone with network access to the target system, making it particularly dangerous in public-facing environments.
Organizations should immediately implement mitigations including upgrading to patched versions of OpenSSL that address the integer underflow condition in the explicit IV calculation logic. The recommended approach involves upgrading to OpenSSL 0.9.8x series (x >= 16), 1.0.0j, or 1.0.1c and later versions, which contain the necessary fixes to prevent the integer underflow conditions. System administrators should also consider implementing network-based mitigations such as firewall rules that limit access to vulnerable services or deploying intrusion detection systems that can identify and block malicious TLS packets. Additional defensive measures include monitoring for unusual network traffic patterns that may indicate exploitation attempts and implementing proper logging to track TLS connection attempts. Organizations should also conduct comprehensive vulnerability assessments to identify all systems running affected OpenSSL versions and prioritize remediation efforts based on risk exposure. The vulnerability aligns with CWE-191 (Integer Underflow) and can be categorized under ATT&CK technique T1499.004 (Endpoint Denial of Service) and potentially T1059.001 (Command and Scripting Interpreter) if exploitation leads to code execution scenarios.