CVE-2008-2377 in gnutls
Summary
by MITRE
Use-after-free vulnerability in the _gnutls_handshake_hash_buffers_clear function in lib/gnutls_handshake.c in libgnutls in GnuTLS 2.3.5 through 2.4.0 allows remote attackers to cause a denial of service (crash) or possibly execute arbitrary code via TLS transmission of data that is improperly used when the peer calls gnutls_handshake within a normal session, leading to attempted access to a deallocated libgcrypt handle.
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Analysis
by VulDB Data Team • 08/16/2019
The CVE-2008-2377 vulnerability represents a critical use-after-free flaw in the GnuTLS library that affects versions 2.3.5 through 2.4.0. This vulnerability resides within the _gnutls_handshake_hash_buffers_clear function located in lib/gnutls_handshake.c, demonstrating a fundamental memory management error that can be exploited remotely. The flaw occurs during TLS transmission when a peer performs a gnutls_handshake operation within a normal session, creating a scenario where memory deallocation and subsequent access create exploitable conditions. This vulnerability type directly maps to CWE-416, which describes the use of freed memory condition, and falls under the broader category of memory safety issues that have been extensively documented in cybersecurity literature. The vulnerability's classification aligns with ATT&CK technique T1059.007 for execution through remote code injection, as it enables potential arbitrary code execution through improper memory handling.
The technical implementation of this vulnerability involves a specific sequence where the _gnutls_handshake_hash_buffers_clear function improperly manages memory buffers during the TLS handshake process. When a peer calls gnutls_handshake during a normal session, the function clears handshake hash buffers but fails to properly manage the lifecycle of associated libgcrypt handles. This creates a situation where a deallocated memory handle is subsequently accessed, leading to undefined behavior that manifests as either a denial of service crash or potential code execution. The flaw specifically exploits the timing gap between memory deallocation and the subsequent access attempt, allowing attackers to manipulate the TLS session state to trigger the vulnerable code path. The vulnerability's impact is amplified by the fact that it can be triggered through normal TLS transmission patterns, making it particularly dangerous in networked environments where TLS connections are common.
The operational impact of CVE-2008-2377 extends beyond simple service disruption to potentially enable remote code execution, making it a severe security concern for systems relying on GnuTLS for secure communications. The vulnerability affects any system running affected versions of GnuTLS that handle TLS connections, including web servers, email servers, and other network services that utilize the library. When exploited, the vulnerability can cause immediate system crashes, leading to denial of service conditions that may be difficult to distinguish from legitimate network failures. However, the potential for arbitrary code execution through this use-after-free condition means that attackers could leverage the vulnerability to gain unauthorized access to affected systems. The attack vector requires only that a remote peer establish a TLS connection and initiate a handshake, making it particularly concerning for services that accept connections from untrusted parties.
Mitigation strategies for CVE-2008-2377 primarily involve immediate patching of affected GnuTLS installations to versions that address the memory management flaw. System administrators should prioritize updating to GnuTLS 2.4.1 or later, where the vulnerability has been resolved through proper memory handling in the _gnutls_handshake_hash_buffers_clear function. Additionally, network administrators should consider implementing connection rate limiting and monitoring for unusual TLS handshake patterns that might indicate exploitation attempts. The vulnerability's nature suggests that defensive measures such as intrusion detection systems should monitor for abnormal memory access patterns or crash conditions in TLS services. Organizations should also conduct thorough inventory checks to identify all systems running affected GnuTLS versions and ensure complete remediation across their infrastructure. Security teams should implement regular vulnerability scanning procedures to detect similar memory management issues in other cryptographic libraries and system components that may be susceptible to analogous use-after-free conditions.