CVE-2008-1950 in gnutls
Summary
by MITRE
Integer signedness error in the _gnutls_ciphertext2compressed function in lib/gnutls_cipher.c in libgnutls in GnuTLS before 2.2.4 allows remote attackers to cause a denial of service (buffer over-read and crash) via a certain integer value in the Random field in an encrypted Client Hello message within a TLS record with an invalid Record Length, which leads to an invalid cipher padding length, aka GNUTLS-SA-2008-1-3.
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Analysis
by VulDB Data Team • 12/30/2024
The vulnerability described in CVE-2008-1950 represents a critical integer signedness error within the GnuTLS cryptographic library implementation. This flaw exists in the _gnutls_ciphertext2compressed function located in lib/gnutls_cipher.c, where improper handling of integer values leads to unpredictable behavior during TLS record processing. The vulnerability specifically affects GnuTLS versions prior to 2.2.4, making it a significant concern for systems relying on older cryptographic libraries for secure communications.
The technical root cause stems from how the function processes the Random field within encrypted Client Hello messages, particularly when these messages are contained within TLS records that exhibit invalid Record Length values. When attackers craft malicious TLS records with malformed data structures, the integer signedness error causes the system to interpret certain values incorrectly, resulting in buffer over-read conditions. This occurs because the system treats signed integers as unsigned during the padding length calculation process, leading to calculations that exceed expected buffer boundaries.
The operational impact of this vulnerability manifests as a remote denial of service condition that can crash the targeted application or system. Attackers can exploit this weakness by sending specially crafted TLS records containing invalid Record Length values and malformed Random fields within Client Hello messages. The resulting buffer over-read causes memory corruption that leads to application crashes or system instability, effectively rendering the service unavailable to legitimate users. This vulnerability particularly affects web servers, mail servers, and any applications that utilize GnuTLS for secure communication protocols.
This vulnerability maps to CWE-195: Signed to Unsigned Conversion Error, which classifies it as a fundamental programming error involving improper type handling in cryptographic implementations. The attack pattern aligns with ATT&CK technique T1499.004: Endpoint Denial of Service, where attackers leverage software vulnerabilities to disrupt service availability. The specific exploitation vector involves manipulating TLS protocol handling to trigger memory corruption through improper integer arithmetic. Organizations should prioritize upgrading to GnuTLS 2.2.4 or later versions to address this vulnerability, as the patch resolves the integer signedness error by ensuring proper handling of unsigned integer values during cipher processing operations.
The broader implications extend beyond immediate service disruption, as this vulnerability demonstrates the critical importance of proper integer handling in cryptographic libraries where memory safety directly impacts system stability. The flaw underscores the need for comprehensive testing of edge cases in TLS implementations, particularly around malformed input handling and buffer boundary conditions. Security practitioners should consider this vulnerability as part of a larger category of memory safety issues that can lead to both denial of service and potential privilege escalation scenarios in poorly configured systems.