CVE-2017-5336 in GnuTLS
Summary
by MITRE
Stack-based buffer overflow in the cdk_pk_get_keyid function in lib/opencdk/pubkey.c in GnuTLS before 3.3.26 and 3.5.x before 3.5.8 allows remote attackers to have unspecified impact via a crafted OpenPGP certificate.
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Analysis
by VulDB Data Team • 10/28/2022
The vulnerability identified as CVE-2017-5336 represents a critical stack-based buffer overflow affecting the GnuTLS cryptographic library. This flaw exists within the cdk_pk_get_keyid function located in the lib/opencdk/pubkey.c file, which is part of the OpenCDK component used for OpenPGP certificate processing. The vulnerability impacts GnuTLS versions prior to 3.3.26 and all 3.5.x versions before 3.5.8, creating a significant security risk for systems relying on OpenPGP certificate handling. The flaw specifically manifests when processing crafted OpenPGP certificates, where malicious input can trigger the buffer overflow condition.
The technical nature of this vulnerability stems from improper bounds checking within the cdk_pk_get_keyid function, which processes public key identifiers from OpenPGP certificates. When a malformed certificate is processed, the function fails to validate the size of incoming data before copying it to a fixed-size stack buffer. This classic buffer overflow condition allows attackers to overwrite adjacent stack memory, potentially leading to arbitrary code execution or application crashes. The vulnerability operates at the application layer and can be exploited remotely through network-based certificate processing operations, making it particularly dangerous in networked environments where certificate validation occurs automatically.
From an operational impact perspective, this vulnerability creates multiple attack vectors that can compromise system integrity and availability. Remote attackers can leverage this flaw to execute arbitrary code on systems processing OpenPGP certificates, potentially gaining unauthorized access to sensitive information or disrupting services. The unspecified impact mentioned in the CVE description reflects the potential for various outcomes including privilege escalation, denial of service, or complete system compromise depending on the execution environment and attack payload. Systems using GnuTLS for OpenPGP certificate validation, particularly those in server environments or applications processing untrusted certificates, face the highest risk of exploitation.
Organizations affected by this vulnerability should prioritize immediate patching of their GnuTLS installations to versions 3.3.26 or 3.5.8 and later. The mitigation strategy should include comprehensive vulnerability scanning to identify systems running vulnerable GnuTLS versions, followed by coordinated patch deployment across all affected environments. Security teams should also implement network monitoring to detect potential exploitation attempts targeting this specific vulnerability, as the attack may not be immediately apparent. Additionally, organizations should consider implementing certificate validation policies that limit processing of untrusted certificates and establish incident response procedures for potential exploitation attempts. This vulnerability aligns with CWE-121 Stack-based Buffer Overflow and can be mapped to ATT&CK technique T1059.007 for command and scripting interpreter, as exploitation may involve code execution through the buffer overflow. The vulnerability demonstrates the critical importance of input validation in cryptographic libraries and highlights the need for regular security updates to protect against known vulnerabilities in widely-used security components.