CVE-2019-11719 in Firefox
Summary
by MITRE
When importing a curve25519 private key in PKCS#8format with leading 0x00 bytes, it is possible to trigger an out-of-bounds read in the Network Security Services (NSS) library. This could lead to information disclosure. This vulnerability affects Firefox ESR < 60.8, Firefox < 68, and Thunderbird < 60.8.
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Analysis
by VulDB Data Team • 11/26/2025
The vulnerability identified as CVE-2019-11719 represents a critical out-of-bounds read flaw within the Network Security Services (NSS) library that processes cryptographic key imports. This issue specifically manifests when handling curve25519 private keys formatted according to the PKCS#8 standard, where the presence of leading zero bytes creates a condition that bypasses normal input validation mechanisms. The flaw exists in the cryptographic processing pipeline of NSS, which is widely utilized across Mozilla products including Firefox ESR, Firefox, and Thunderbird, making it a significant concern for organizations relying on these browsers and email clients.
The technical implementation of this vulnerability stems from improper boundary checking during the parsing of private key data structures. When NSS encounters a curve25519 private key in PKCS#8 format containing leading 0x00 bytes, the parsing algorithm fails to properly validate the length of the key data before accessing memory regions. This allows an attacker to craft malicious key files that cause the library to read beyond the allocated buffer boundaries, potentially exposing sensitive memory contents including cryptographic keys, session data, or other confidential information. The vulnerability is classified under CWE-129 as an "Improper Validation of Array Index" and aligns with ATT&CK technique T1552.001 for Unsecured Credentials, as it could lead to credential exposure through memory disclosure.
The operational impact of this vulnerability extends beyond simple information disclosure, as it provides attackers with potential access to cryptographic material that could compromise the security of encrypted communications. Organizations running affected versions of Firefox ESR, Firefox, or Thunderbird are particularly vulnerable since these browsers rely on NSS for their cryptographic operations. The flaw could be exploited in scenarios involving man-in-the-middle attacks, session hijacking, or credential theft, especially when users import or receive encrypted content from untrusted sources. Attackers could leverage this vulnerability to gain access to sensitive data that should remain protected within the application's memory space.
Mitigation strategies for CVE-2019-11719 primarily involve updating to patched versions of the affected software components. Mozilla has released security updates for Firefox ESR 60.8, Firefox 68, and Thunderbird 60.8, which include fixes for the out-of-bounds read condition in NSS. Organizations should prioritize immediate deployment of these patches across their infrastructure to eliminate the risk of exploitation. Additionally, network administrators should implement monitoring for suspicious key import activities and consider implementing additional security controls such as certificate pinning and enhanced input validation for cryptographic operations. The vulnerability also highlights the importance of proper input sanitization in cryptographic libraries and demonstrates the need for comprehensive testing of edge cases in cryptographic processing functions to prevent similar issues in the future.