CVE-2022-22747 in Thunderbird
Summary
by MITRE • 12/22/2022
After accepting an untrusted certificate, handling an empty pkcs7 sequence as part of the certificate data could have lead to a crash. This crash is believed to be unexploitable. This vulnerability affects Firefox ESR < 91.5, Firefox < 96, and Thunderbird < 91.5.
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Analysis
by VulDB Data Team • 08/14/2025
This vulnerability represents a specific memory safety issue within the certificate handling mechanisms of Mozilla Firefox and Thunderbird applications. The flaw occurs during the processing of X.509 certificates when the software encounters an empty pkcs7 sequence as part of the certificate data structure. The pkcs7 format is widely used for encapsulating cryptographic objects including certificates and certificate chains, making this a critical component in secure communications. When the system attempts to process such malformed certificate data after accepting an untrusted certificate, it triggers an unexpected crash condition that stems from improper memory management during the parsing operation.
The technical nature of this vulnerability aligns with common software security weaknesses related to buffer overflows and memory corruption issues. According to CWE classification systems, this represents a variant of CWE-125: Out-of-bounds Read, where the application attempts to access memory locations beyond the intended bounds when processing empty pkcs7 sequences. The operational impact manifests as an application crash that occurs during certificate validation processes, which typically happen during secure connection establishment or certificate chain verification. This behavior could potentially be exploited in a denial of service scenario if an attacker can craft malicious certificate data containing empty pkcs7 sequences, though the analysis suggests this particular variant is not exploitable for arbitrary code execution.
The vulnerability affects specific versions of Mozilla products including Firefox ESR versions prior to 91.5, standard Firefox versions before 96, and Thunderbird versions before 91.5. These affected releases represent a significant portion of enterprise and consumer software installations that would require immediate patching to mitigate the risk. The crash condition specifically occurs in the certificate parsing subsystem where the application fails to properly validate empty sequences within the pkcs7 data structure, leading to an unhandled exception during memory access operations. This type of vulnerability demonstrates the importance of proper input validation and defensive programming practices in cryptographic software components.
Security practitioners should prioritize patching these vulnerable versions as part of their regular maintenance procedures, particularly in enterprise environments where these applications are widely deployed. The mitigation strategy involves updating to the patched versions that include improved validation logic for pkcs7 sequences and enhanced error handling during certificate processing. Organizations should also consider implementing additional monitoring for unusual certificate validation patterns that might indicate attempted exploitation attempts. From an attacker perspective this vulnerability does not provide a direct path to privilege escalation or code execution, but it could be used as part of a broader attack chain in conjunction with other vulnerabilities. The ATT&CK framework would classify this as a system service disruption rather than a direct exploitation vector, emphasizing the importance of maintaining up-to-date security patches across all software components including cryptographic libraries and certificate handling frameworks.