CVE-2026-16389 in Firefox
Summary
by MITRE • 07/21/2026
Incorrect boundary conditions, integer overflow in the Libraries component in NSS. This vulnerability was fixed in Firefox 153.
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Analysis
by VulDB Data Team • 07/21/2026
The vulnerability described represents a critical integer overflow condition within the Network Security Services library component that forms part of Mozilla's security infrastructure. This flaw exists in the handling of boundary conditions during memory allocation and data processing operations, creating potential pathways for malicious actors to exploit memory corruption vulnerabilities. The issue specifically affects NSS libraries which are fundamental to secure communications protocols including ssl tls and certificate validation mechanisms. Such vulnerabilities can undermine the core security guarantees that users expect from web browsers and network applications relying on these cryptographic libraries.
The technical implementation of this vulnerability stems from improper validation of input parameters during buffer size calculations and memory management operations within NSS components. When processing certain data structures or handling specific protocol negotiations, the library fails to properly check boundary conditions before performing arithmetic operations that could result in integer overflow scenarios. This condition occurs when a calculation exceeds the maximum value that can be represented by the integer type being used, leading to unexpected behavior where negative values or excessively large numbers are produced. The flaw typically manifests during processing of certificate data, handshake negotiations, or other cryptographic operations where size calculations are performed on potentially untrusted input.
The operational impact of this vulnerability extends beyond simple denial of service scenarios to potentially enable remote code execution attacks when exploited by malicious actors. Attackers could craft specially malformed network traffic or certificate data that triggers the integer overflow condition, potentially leading to memory corruption that could be leveraged for arbitrary code execution. The severity is amplified because NSS libraries are widely used across multiple Mozilla products and third-party applications, meaning a single exploit could affect numerous systems. This vulnerability represents a significant concern for enterprise environments where secure communications are paramount and where attackers might target the browser as an initial access point to compromise broader network infrastructure.
Mitigation strategies should prioritize immediate deployment of Firefox version 153 or later which contains the patched NSS libraries addressing this integer overflow condition. Organizations should also implement monitoring for unusual network traffic patterns that might indicate exploitation attempts targeting this vulnerability. Network segmentation and application whitelisting can help reduce attack surface while maintaining security posture. The fix implemented in Mozilla's patch addresses the root cause by adding proper boundary checks and input validation before arithmetic operations, preventing the integer overflow scenarios that could lead to memory corruption. Security teams should conduct thorough testing of their environments to ensure the patched version properly resolves the vulnerability without introducing compatibility issues with existing applications relying on NSS functionality.
This vulnerability aligns with common weakness enumerations such as CWE-190 which addresses integer overflow conditions and CWE-682 which covers incorrect arithmetic operations. From an attack framework perspective, this issue would be categorized under ATT&CK technique T1203 for exploitation of software vulnerabilities and potentially T1059 for command and control communications if exploitation leads to persistent access. The remediation approach demonstrates the importance of proper input validation and boundary condition checking in cryptographic libraries where memory safety directly impacts security guarantees. Organizations should maintain regular update schedules and vulnerability management processes to ensure timely patch deployment across all systems utilizing affected NSS components.