CVE-2026-6767 Overview
CVE-2026-6767 is a memory corruption vulnerability affecting the Libraries component in Mozilla's Network Security Services (NSS). This vulnerability, classified under CWE-119 (Improper Restriction of Operations within the Bounds of a Memory Buffer), exists within the NSS cryptographic library used by Firefox and Thunderbird. The issue allows potential information disclosure through improper memory handling operations in affected versions of Mozilla products.
Critical Impact
An attacker exploiting this vulnerability could potentially access sensitive information from memory through network-based attacks without requiring user interaction or authentication.
Affected Products
- Mozilla Firefox versions prior to 150
- Mozilla Firefox ESR versions prior to 115.35 and 140.10
- Mozilla Thunderbird versions prior to 150 and 140.10
Discovery Timeline
- April 21, 2026 - CVE-2026-6767 published to NVD
- April 22, 2026 - Last updated in NVD database
Technical Details for CVE-2026-6767
Vulnerability Analysis
This vulnerability resides in the NSS (Network Security Services) Libraries component, which provides cryptographic functionality for Mozilla products including Firefox and Thunderbird. The flaw involves improper boundary checking operations that can lead to unauthorized memory access. The vulnerability can be triggered remotely over a network connection without requiring any privileges or user interaction, making it particularly concerning for browser-based attack scenarios.
The attack surface is significant given that NSS handles critical security operations including SSL/TLS connections, certificate validation, and cryptographic operations. Any weakness in these components can have cascading effects on the overall security posture of affected applications.
Root Cause
The root cause of CVE-2026-6767 is improper restriction of operations within the bounds of a memory buffer (CWE-119). This class of vulnerability occurs when software performs operations on a memory buffer without properly ensuring that read or write operations stay within the allocated boundaries. In the context of the NSS Libraries component, this boundary condition error allows potential information leakage through out-of-bounds memory access.
Attack Vector
The vulnerability is exploitable over the network without requiring authentication or user interaction. An attacker could potentially craft malicious network traffic or content that triggers the vulnerable code path in the NSS Libraries component. When processed by an affected version of Firefox or Thunderbird, the improper boundary handling could expose portions of memory that should not be accessible, potentially leaking sensitive information such as cryptographic keys, session tokens, or other confidential data.
The exploitation scenario typically involves:
- The attacker delivers specially crafted content to a victim's browser or email client
- The NSS library processes this content without proper boundary validation
- Memory contents outside the intended buffer are exposed to the attacker
- Sensitive information is potentially disclosed through the network connection
Detection Methods for CVE-2026-6767
Indicators of Compromise
- Unusual network traffic patterns involving malformed SSL/TLS handshakes or certificate data
- Unexpected memory access violations or crashes in Firefox or Thunderbird processes
- Anomalous behavior in NSS-related system calls or library operations
Detection Strategies
- Monitor application crash reports and memory access violations related to Firefox, Thunderbird, or NSS library components
- Implement network intrusion detection rules to identify potential exploitation attempts targeting NSS vulnerabilities
- Deploy endpoint detection solutions that can identify suspicious memory access patterns in browser processes
Monitoring Recommendations
- Enable verbose logging for SSL/TLS operations to detect anomalous certificate or handshake processing
- Monitor for unexpected child process spawning or memory allocation patterns in Mozilla applications
- Review system event logs for signs of memory corruption or access violations in affected products
How to Mitigate CVE-2026-6767
Immediate Actions Required
- Update Mozilla Firefox to version 150 or later immediately
- Update Mozilla Firefox ESR to version 115.35 or 140.10 depending on your ESR channel
- Update Mozilla Thunderbird to version 150 or 140.10 depending on your release channel
- Review and apply all pending security updates for affected Mozilla products
Patch Information
Mozilla has released security patches addressing this vulnerability in the following versions:
- Firefox 150 - Full patch for standard release channel
- Firefox ESR 115.35 - Patch for Extended Support Release 115.x branch
- Firefox ESR 140.10 - Patch for Extended Support Release 140.x branch
- Thunderbird 150 - Full patch for standard release
- Thunderbird 140.10 - Patch for ESR branch
For detailed information, consult the official Mozilla Security Advisories:
- Mozilla Security Advisory MFSA-2026-30
- Mozilla Security Advisory MFSA-2026-31
- Mozilla Security Advisory MFSA-2026-32
- Mozilla Security Advisory MFSA-2026-33
- Mozilla Security Advisory MFSA-2026-34
Technical details are available in the Mozilla Bug Report #2023209.
Workarounds
- Restrict network access for affected applications until patches can be applied
- Consider using alternative browsers temporarily in high-security environments where immediate patching is not feasible
- Implement network-level filtering to block potentially malicious content targeting NSS vulnerabilities
# Verify installed Firefox version on Linux
firefox --version
# Update Firefox on Debian/Ubuntu systems
sudo apt update && sudo apt upgrade firefox
# Update Firefox on RHEL/CentOS/Fedora systems
sudo dnf update firefox
# Verify installed Thunderbird version
thunderbird --version
Disclaimer: This content was generated using AI. While we strive for accuracy, please verify critical information with official sources.
