CVE-2025-3031 in Thunderbird
Summary
by MITRE • 04/01/2025
An attacker could read 32 bits of values spilled onto the stack in a JIT compiled function. This vulnerability was fixed in Firefox 137 and Thunderbird 137.
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Analysis
by VulDB Data Team • 04/15/2026
This vulnerability represents a critical information disclosure flaw in the JavaScript engine of Mozilla Firefox and Thunderbird applications. The issue manifests within the Just-In-Time compilation process where the runtime environment optimizes JavaScript code execution. When the JIT compiler processes certain functions, it may spill temporary values onto the stack during optimization phases, creating a scenario where sensitive data from previous operations could be inadvertently exposed through memory access patterns.
The technical nature of this vulnerability stems from improper memory management during JIT compilation cycles. Specifically, the flaw allows an attacker to extract 32 bits of data that were previously stored on the stack but not properly cleared or overwritten. This occurs because the compiler's optimization routines do not adequately sanitize stack memory regions before reusing them for new operations. The vulnerability is particularly concerning as it operates at the compiler level where memory layout and optimization decisions directly impact security boundaries.
The operational impact of this vulnerability extends beyond simple information disclosure, as the leaked data could potentially include sensitive information such as cryptographic keys, session tokens, or other confidential values that were temporarily stored in memory. Attackers could exploit this weakness by crafting malicious JavaScript code that triggers the specific JIT compilation path where stack values are spilled, then read the exposed data through memory access techniques. This represents a classic case of a memory safety vulnerability that could be leveraged for privilege escalation or data theft in targeted attacks.
This vulnerability aligns with CWE-248, which addresses "Uncaught Exception" conditions where improper handling of exceptional cases leads to information exposure. The flaw also relates to ATT&CK technique T1059.007 for "Command and Scripting Interpreter: JavaScript" as it specifically affects JavaScript execution environments. The mitigation strategy involves proper stack memory sanitization during JIT compilation and ensuring that spilled values are properly cleared before reuse. The fix implemented in Firefox and Thunderbird version 137 addresses this by modifying the JIT compiler's memory management routines to prevent the exposure of stale data during stack operations. Organizations should immediately update to these patched versions and monitor for any potential exploitation attempts targeting this specific memory disclosure vulnerability in their browser environments.