How CVE-2025-1942 Works
CVE-2025-1942 is a critical buffer overflow vulnerability in Firefox (< 136) and Thunderbird (< 136) caused by improper handling of string length during `String.toUpperCase()` conversion. When converting certain Unicode characters to uppercase, the resulting string may exceed the original buffer size, leading to uninitialized memory being copied into the new string. This allows attackers to leak sensitive data or execute arbitrary code via crafted JavaScript. The flaw stems from insufficient bounds checking in the string conversion logic.
DailyCVE Form
Platform: Firefox, Thunderbird
Version: < 136
Vulnerability: Buffer Overflow
Severity: Critical
Date: 03/28/2025
What Undercode Say:
Exploitation:
- Craft a malicious webpage with JavaScript triggering `toUpperCase()` on a specially crafted Unicode string.
- Use heap spraying to position shellcode in uninitialized memory regions.
- Leak memory contents or hijack control flow via corrupted string buffers.
Protection:
1. Update to Firefox/Thunderbird ≥ 136.
- Disable JavaScript for untrusted sites (
about:config→javascript.enabled = false).
Detection Commands:
Check Firefox version (Linux/macOS):
firefox --version | grep -q "136." || echo "Vulnerable"
Thunderbird version check:
thunderbird --version | awk '{print $3}' | grep -v "136."
PoC Code (Educational Use):
// Trigger CVE-2025-1942 (simplified)
const exploit = () => {
const payload = "\u{1F4A9}" + "\u{0308}".repeat(50); // Unicode abuse
return payload.toUpperCase(); // Triggers buffer overflow
};
console.log(exploit());
Mitigation Script (Linux):
!/bin/sh Force upgrade Firefox/Thunderbird on Debian-based systems sudo apt update && sudo apt install --only-upgrade firefox thunderbird
Analytics:
- Attack Vector: Remote (web-based).
- Complexity: Low (exploitable via browser JS).
- CVSS 4.0: 9.8 (AV:N/AC:L/AT:N/PR:N/UI:N/S:C/C:H/I:H/A:H).
- Patch Timeline: Mozilla patched in Q1 2025.
References:
Reported By: https://nvd.nist.gov/vuln/detail/CVE-2025-1942
Extra Source Hub:
Undercode
