CVE-2016-9074 in Firefox
Summary
by MITRE
An existing mitigation of timing side-channel attacks is insufficient in some circumstances. This issue is addressed in Network Security Services (NSS) 3.26.1. This vulnerability affects Thunderbird < 45.5, Firefox ESR < 45.5, and Firefox < 50.
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Analysis
by VulDB Data Team • 11/25/2025
The vulnerability identified as CVE-2016-9074 represents a critical weakness in the cryptographic implementation of Network Security Services (NSS) that undermines existing defenses against timing side-channel attacks. This issue manifests when the cryptographic operations within NSS fail to properly mitigate timing variations that could reveal sensitive information about cryptographic keys or operations. The vulnerability specifically targets the insufficient implementation of countermeasures that should prevent attackers from inferring cryptographic secrets through careful measurement of execution time differences during cryptographic operations. The weakness affects multiple Mozilla products including Thunderbird versions prior to 45.5, Firefox Extended Support Release versions before 45.5, and standard Firefox versions before 50, indicating a widespread impact across the Mozilla ecosystem. This vulnerability falls under the broader category of side-channel attacks that exploit information leaked through timing variations rather than direct cryptographic weaknesses.
The technical flaw in NSS stems from inadequate timing side-channel mitigations that should have been implemented to prevent attackers from measuring execution time differences during cryptographic operations such as RSA decryption or elliptic curve operations. When these operations are performed without proper constant-time implementations, attackers can observe variations in processing time that correlate with the values of secret keys or intermediate cryptographic states. The vulnerability occurs because the cryptographic primitives within NSS do not sufficiently randomize execution paths or introduce timing delays that would mask the actual processing time of cryptographic operations. This weakness allows adversaries to perform statistical analysis on timing measurements to reconstruct cryptographic keys or other sensitive data. The issue demonstrates a failure in applying established cryptographic best practices for timing attack resistance, which is a fundamental requirement for secure cryptographic implementations. According to CWE-398, this vulnerability represents an insufficient implementation of security features that should have been in place to prevent side-channel attacks.
The operational impact of CVE-2016-9074 is significant for users of affected Mozilla products, as it creates a potential avenue for sophisticated attackers to compromise cryptographic security. Attackers could exploit this vulnerability to perform key recovery attacks against TLS connections, SSL certificates, or other cryptographic operations that rely on NSS for security. The vulnerability is particularly concerning because it affects long-term support versions of Firefox and Thunderbird, meaning that users who have not updated their software remain exposed to potential attacks. The timing variations that enable this attack can be measured even over network connections, making it a remotely exploitable vulnerability. Organizations that rely on these browsers for secure communications, email, or web browsing are at risk of having their cryptographic protections undermined. The vulnerability also impacts the trust model of the internet, as it could potentially allow attackers to impersonate legitimate services or decrypt sensitive communications. According to ATT&CK framework technique T1074, this vulnerability enables data extraction through timing-based side-channel information gathering that could be used in conjunction with other attack vectors to compromise security systems.
The mitigation for CVE-2016-9074 requires immediate updates to affected versions of Mozilla products to versions that include proper timing side-channel mitigations. Users must upgrade to Thunderbird 45.5 or later, Firefox ESR 45.5 or later, and Firefox 50 or later to address the vulnerability. System administrators should prioritize patching affected systems and ensure that all users of these browsers are updated to secure versions. Organizations should also implement monitoring for potential exploitation attempts and consider additional security measures such as network segmentation or intrusion detection systems to detect anomalous timing patterns that might indicate exploitation attempts. The patch released with NSS 3.26.1 includes proper constant-time implementations and timing randomization techniques that prevent attackers from measuring meaningful timing variations during cryptographic operations. Security teams should also review their cryptographic implementations and ensure that similar timing side-channel vulnerabilities are not present in other systems or applications that perform cryptographic operations. The vulnerability highlights the importance of continuous security auditing and the need for robust implementation of cryptographic countermeasures that are resistant to various attack vectors including timing-based side-channel analysis.