CVE-2026-10701: Firefox Text Rendering Memory Disclosure Vulnerability

Technical summary

CVE-2026-10701 is a boundary condition vulnerability in Firefox's Graphics: Text component that stems from improper validation of buffer limits (CWE-119: Buffer Over-read, CWE-131: Incorrect Buffer Dimension Calculation). The flaw permits an attacker to trigger out-of-bounds memory access over the network with no authentication or user action required, leading to information disclosure. The CVSS 3.1 vector (AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N) reflects high confidentiality impact with low attack complexity, though integrity and availability are not compromised.

Business impact

Organizations with users running vulnerable Firefox versions face exposure of sensitive data processed by the browser, including cached credentials, session tokens, or private web content. While the vulnerability does not enable code execution or system takeover, the confidentiality breach could lead to secondary attacks or unauthorized access to protected resources. Patches must be deployed promptly to reduce the window of exposure, particularly for users handling sensitive information in the browser.

Affected systems

Mozilla Firefox versions prior to 151.0.3 are vulnerable. All platforms running affected versions are at risk; the network-based attack vector means no local access is required. Users on older release branches or extended support versions should verify patch availability for their specific track.

Exploitability

This vulnerability is exploitable over the network without user interaction or elevated privileges, making it relatively accessible to attackers. However, it does not appear on the CISA Known Exploited Vulnerabilities (KEV) catalog, suggesting that as of the source data date, widespread active exploitation has not been confirmed in the wild. Organizations should assume exploitation is feasible and prioritize patching accordingly.

Remediation

Update Firefox to version 151.0.3 or later. Users should enable automatic updates if available. Verify the installed version in Firefox menu > Help > About Firefox and confirm it displays 151.0.3 or higher. For enterprise deployments, push updates via Group Policy or mobile device management as appropriate for your platform.

Patch guidance

Mozilla has released Firefox 151.0.3 containing the fix for this boundary condition flaw. Patches are available immediately upon release through Mozilla's official channels. Users on standard release cycles will receive the update automatically; those on Extended Support Release (ESR) or Rapid Release should verify their specific patch availability timeline on Mozilla's security advisories page. No workarounds are available; patching is the only mitigation.

Detection guidance

Monitor for Firefox crashes or unexpected memory access errors in logs, particularly on systems processing untrusted web content. Network-based detection is difficult without application-level logging. Endpoint management tools should report Firefox version compliance to identify unpatched instances across your environment. Consider blocking vulnerable Firefox versions via policy where feasible during the patching window.

Why prioritize this

HIGH severity with CVSS 7.5 reflects high confidentiality risk combined with a low barrier to exploitation. The network attack vector and lack of authentication requirements elevate urgency. While not yet on the KEV catalog, the ease of exploitation makes rapid patching critical for organizations with browser-based workflows handling sensitive data.

Risk score, explained

The CVSS 3.1 score of 7.5 is driven by network accessibility (AV:N), low attack complexity (AC:L), and high confidentiality impact (C:H). The absence of integrity and availability impact limits the score, but the information disclosure risk is substantial. Organizations handling credentials or proprietary data in the browser should treat this as a priority patch regardless of the numerical score.

Frequently asked questions