CVE-2026-10701: Firefox Buffer Overflow Vulnerability

CVE-2026-10701 Overview

CVE-2026-10701 is a high-severity vulnerability in the Graphics: Text component of Mozilla Firefox. The flaw stems from incorrect boundary conditions [CWE-119] in text rendering logic. Mozilla resolved the issue in Firefox 151.0.3.

A remote attacker can trigger the condition by serving crafted web content. Exploitation requires no privileges and no user interaction beyond visiting an attacker-controlled page. The primary impact is high confidentiality loss, consistent with out-of-bounds memory access in the graphics text path.

Critical Impact

Remote attackers can exploit improper boundary checks in Firefox text rendering to read sensitive in-process memory without authentication or user interaction.

Affected Products

• Mozilla Firefox versions prior to 151.0.3
• Firefox builds on all supported desktop platforms shipping the vulnerable Graphics: Text component
• Downstream distributions bundling pre-151.0.3 Firefox binaries

Discovery Timeline

• 2026-06-02 - CVE-2026-10701 published to NVD
• 2026-06-03 - Last updated in NVD database
• Mozilla Security Advisory - Published as MFSA-2026-54

Technical Details for CVE-2026-10701

Vulnerability Analysis

The vulnerability is classified under [CWE-119] (Improper Restriction of Operations within the Bounds of a Memory Buffer). It resides in the Graphics: Text subsystem of Firefox, which handles glyph layout, shaping, and rasterization. Incorrect boundary checks allow operations to reference memory outside intended buffer limits.

The CVSS vector indicates a confidentiality-only impact with no effect on integrity or availability. This profile is typical of out-of-bounds read conditions, where an attacker can disclose adjacent process memory but cannot directly modify state or crash the browser reliably. Disclosed memory can include text fragments, pointers, or tokens that aid further exploitation.

Mozilla classifies the issue as fixed in Firefox 151.0.3. The EPSS probability is 0.031%, reflecting low observed exploitation activity at publication time.

Root Cause

The defect originates in text-handling code that fails to correctly validate index or length values before accessing buffer memory. When the boundary check is incorrect, the code reads beyond the allocated region while processing crafted text input. This pattern is common in glyph shaping, font metric calculation, and Unicode segmentation routines.

Attack Vector

The attack vector is network-based. An attacker hosts a malicious page containing crafted text, font references, or DOM content that triggers the vulnerable path during rendering. When a victim visits the page in an unpatched Firefox build, the content drives the renderer through the flawed boundary check.

No authentication is required, and the attack complexity is low. Exploitation succeeds against the user privilege level of the running browser process. Successful exploitation yields disclosure of in-process memory without requiring sandbox escape.

No verified public proof-of-concept is available. See the Mozilla Bug Report #2038537 for the upstream technical discussion.

Detection Methods for CVE-2026-10701

Indicators of Compromise

• Firefox process versions reporting a build earlier than 151.0.3 on managed endpoints
• Browser telemetry showing renderer crashes or memory anomalies after visiting untrusted pages with heavy text or font content
• Outbound connections to attacker-controlled domains immediately preceding renderer instability

Detection Strategies

• Inventory installed Firefox versions across the fleet and flag any build older than 151.0.3
• Correlate web proxy logs with browser crash reports to identify pages that may target the Graphics: Text path
• Monitor for unusual child process behavior from firefox.exe or firefox binaries following navigation events

Monitoring Recommendations

• Centralize browser version telemetry in a SIEM or data lake to maintain real-time patch posture
• Alert on renderer process exits with abnormal exit codes correlated with specific URLs
• Track Mozilla advisory feeds and ingest MFSA-2026-54 details into vulnerability management workflows

How to Mitigate CVE-2026-10701

Immediate Actions Required

• Update all Firefox installations to version 151.0.3 or later without delay
• Push the update through enterprise management tooling such as Group Policy, Intune, Jamf, or configuration management systems
• Verify update completion by confirming the about:support build identifier on a sample of endpoints

Patch Information

Mozilla released the fix in Firefox 151.0.3. Administrators should consult Mozilla Security Advisory MFSA-2026-54 for the authoritative remediation guidance and the corresponding Mozilla Bug Report #2038537 for upstream context.

Workarounds

• Restrict browsing to trusted sites until patching completes, using web filtering or proxy allowlists
• Disable JavaScript on untrusted origins through enterprise policy where feasible to reduce attacker control over the rendering pipeline
• Apply browser hardening baselines that limit exposure of high-risk users to arbitrary external content

# Verify installed Firefox version on Linux endpoints
firefox --version

# Example enterprise policy file enforcing minimum version awareness (policies.json)
{
  "policies": {
    "DisableAppUpdate": false,
    "AppAutoUpdate": true
  }
}