CVE-2017-5462 in Firefox
Summary
by MITRE
A flaw in DRBG number generation within the Network Security Services (NSS) library where the internal state V does not correctly carry bits over. The NSS library has been updated to fix this issue to address this issue and Firefox ESR 52.1 has been updated with NSS version 3.28.4. This vulnerability affects Thunderbird < 52.1, Firefox ESR < 45.9, Firefox ESR < 52.1, and Firefox < 53.
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Analysis
by VulDB Data Team • 11/26/2025
The vulnerability described in CVE-2017-5462 represents a critical weakness in the cryptographically secure random number generation mechanism within the Network Security Services (NSS) library. This flaw specifically impacts the Deterministic Random Bit Generator (DRBG) implementation, which is fundamental to generating secure cryptographic keys, certificates, and other security-sensitive values. The issue manifests in the internal state management of the DRBG algorithm where the variable V fails to properly propagate bits during the generation process, creating predictable patterns that compromise the randomness of the output. This vulnerability affects a wide range of Mozilla products including Thunderbird, Firefox ESR, and standard Firefox releases, indicating the widespread impact of the flawed random number generation.
The technical root cause of this vulnerability can be categorized under CWE-330, which specifically addresses insufficient entropy in random number generation. The flaw occurs during the internal state update process of the DRBG algorithm where the carry bit operations are incorrectly implemented, leading to reduced entropy and predictable sequences in the generated random numbers. This type of vulnerability directly undermines the cryptographic security model because random number generators are expected to produce outputs that are statistically independent and uniformly distributed. When the carry mechanism fails, it creates deterministic patterns that attackers can potentially exploit to predict future outputs or reverse-engineer the internal state, thereby breaking the fundamental security assumptions of cryptographic systems relying on this library.
The operational impact of this vulnerability extends across multiple Mozilla products and their respective versions, creating a significant security risk for organizations and individuals using affected software. The vulnerability affects Thunderbird versions prior to 52.1, Firefox ESR versions before 45.9 and 52.1, and standard Firefox releases before version 53, indicating that a substantial portion of the user base was potentially exposed. This weakness could enable attackers to compromise SSL/TLS connections, forge digital signatures, break encryption keys, or predict cryptographic tokens used for authentication purposes. The vulnerability particularly affects systems where the NSS library is used for cryptographic operations, including web browsers, email clients, and any applications that rely on secure random number generation for security protocols.
Mitigation strategies for CVE-2017-5462 primarily involve immediate software updates to versions that contain the patched NSS library implementation. The recommended remediation includes upgrading to Firefox ESR 52.1 or later versions that incorporate NSS version 3.28.4, which contains the corrected DRBG implementation. Organizations should also consider implementing additional security measures such as monitoring for unusual cryptographic behavior, conducting vulnerability assessments of systems using affected software, and ensuring that all Mozilla-based applications are kept current with security patches. From an ATT&CK framework perspective, this vulnerability maps to techniques involving credential access and defense evasion through cryptographic attacks, making it particularly concerning for environments where secure communications and authentication are critical. The patch addresses the underlying implementation error by correcting the bit carry operations in the DRBG state management, restoring proper entropy and cryptographic strength to the random number generation process.