CVE-2011-3207 in OpenSSL
Summary
by MITRE
crypto/x509/x509_vfy.c in OpenSSL 1.0.x before 1.0.0e does not initialize certain structure members, which makes it easier for remote attackers to bypass CRL validation by using a nextUpdate value corresponding to a time in the past.
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Analysis
by VulDB Data Team • 08/06/2024
The vulnerability described in CVE-2011-3207 represents a critical flaw in OpenSSL's certificate validation mechanism that specifically affects versions 1.0.x prior to 1.0.0e. This issue resides within the crypto/x509/x509_vfy.c file and stems from improper initialization of structure members during certificate revocation list processing. The flaw fundamentally undermines the integrity of X.509 certificate validation by creating a condition where the system fails to properly validate the temporal aspects of certificate revocation information. When a certificate revocation list contains a nextUpdate value set to a past timestamp, the uninitialized structure members allow the validation process to incorrectly accept this invalid data, thereby permitting revoked certificates to be considered valid. This vulnerability directly impacts the security of SSL/TLS implementations that rely on OpenSSL for certificate verification and certificate revocation checking.
The technical implementation of this vulnerability involves the failure to properly initialize certain members of the X509_CRL structure during the certificate validation process. When OpenSSL processes a certificate revocation list, it should validate that the nextUpdate field contains a future timestamp indicating when the next revocation list update will occur. However, due to uninitialized memory regions, the validation logic can be bypassed when the nextUpdate field contains a past timestamp, allowing the system to accept outdated or maliciously constructed revocation information. This issue falls under the CWE-665 Improper Initialization category, which specifically addresses situations where software fails to properly initialize data structures, leading to unpredictable behavior and potential security vulnerabilities. The improper initialization creates a condition where the system's validation logic becomes unreliable and can be manipulated by attackers who understand the memory layout and validation process.
The operational impact of CVE-2011-3207 is significant for any system relying on OpenSSL for secure communications, particularly those implementing certificate-based authentication and revocation checking. Attackers can exploit this vulnerability to bypass certificate revocation checking by crafting certificate revocation lists with past-dated nextUpdate fields, effectively allowing compromised certificates to remain trusted indefinitely. This creates a window of opportunity for man-in-the-middle attacks, where attackers can use compromised certificates that should have been revoked but are accepted due to the flawed validation process. The vulnerability affects the core security assurances provided by certificate-based systems and can undermine the entire chain of trust that SSL/TLS protocols depend upon. Systems that implement certificate revocation checking, including web servers, email servers, and any application using OpenSSL for secure communications, are potentially vulnerable to this attack vector.
Mitigation strategies for CVE-2011-3207 require immediate deployment of OpenSSL version 1.0.0e or later, which contains the necessary patches to properly initialize the affected structure members. Organizations should conduct comprehensive vulnerability assessments to identify systems running vulnerable OpenSSL versions and prioritize their patching efforts. Additionally, security monitoring should be enhanced to detect anomalous certificate revocation list patterns that might indicate exploitation attempts. The fix implemented in OpenSSL 1.0.0e specifically addresses the uninitialized memory issue by ensuring proper initialization of the structure members before validation occurs. Security practitioners should also consider implementing additional monitoring for certificate validation failures and establish procedures for regular security updates to prevent similar vulnerabilities from occurring in the future. This vulnerability demonstrates the critical importance of proper memory initialization in security-critical code and aligns with ATT&CK technique T1552.001 for credential access through improper certificate validation and T1071.004 for application layer protocol manipulation. Organizations should maintain updated security patches and conduct regular vulnerability assessments to protect against similar issues in their cryptographic implementations.