Information disclosure via partial JIT return write
Published Jul 22, 2025 · Updated Apr 13, 2026
Uninitialized stack data in Firefox and Thunderbird allows remote attackers to disclose process memory through crafted web content. IonMonkey-JIT writes only the low 32 bits of a 64-bit return slot on the stack, while Baseline-JIT reads the full slot and consumes uninitialized upper bits. Exploitation requires a 64-bit build and user interaction with attacker-controlled content; normal Thunderbird mail reading disables scripting, limiting exposure to browser or browser-like contexts.
Summary
What happened
Uninitialized stack data in Firefox and Thunderbird allows remote attackers to disclose process memory through crafted web content. IonMonkey-JIT writes only the low 32 bits of a 64-bit return slot on the stack, while Baseline-JIT reads the full slot and consumes uninitialized upper bits. Exploitation requires a 64-bit build and user interaction with attacker-controlled content; normal Thunderbird mail reading disables scripting, limiting exposure to browser or browser-like contexts.
The record
- CVE
- CVE-2025-8027
- Published
- Jul 22, 2025
- Updated
- Apr 13, 2026
- Vendor
- Unknown vendor
- Product
- Unknown product
- Classifications
- CWE-457, T1203
- Attack vector
- network
- Privileges
- unauthenticated
Timeline
How it unfolded
- Jul 22, 2025CVE publishedPublication date reported by the CVE source.
- Apr 13, 2026Record updatedLatest update available in the CVE record.
Exploitability
Present is not the same as exploitable
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What is affected?
Affected products and versions are unavailable in this record.
Attacks
What attackers are doing with it
Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.
Weakness, pattern, technique
Public exploit references
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Technologies
Your stack
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Your stack
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