CVE-2026-4371
Modified
Modified - Updated After Analysis
Buffer Overflow in Thunderbird Mail Parser Causes Crash, Data Leak
Vulnerability report for CVE-2026-4371, including description, CVSS score, EPSS score, affected products, exploitability, helpful resources, and attack-flow context.
Publication date: 2026-03-24
Last updated on: 2026-06-30
Assigner: Mozilla Corporation
Description
Description
A malicious mail server could send malformed strings with negative lengths, causing the parser to read memory outside the buffer. If a mail server or connection to a mail server were compromised, an attacker could cause the parser to malfunction, potentially crashing Thunderbird or leaking sensitive data. This vulnerability was fixed in Thunderbird 149 and Thunderbird 140.9.
CVSS Scores
EPSS Scores
| Probability: | |
| Percentile: |
Meta Information
Affected Vendors & Products
| Vendor | Product | Version / Range |
|---|---|---|
| mozilla | thunderbird | to 149.0 (exc) |
| mozilla | thunderbird | to 140.9.0 (exc) |
Helpful Resources
Exploitability
CWE
KEV
| CWE ID | Description |
|---|---|
| CWE-126 | The product reads from a buffer using buffer access mechanisms such as indexes or pointers that reference memory locations after the targeted buffer. |
| CWE-130 | The product parses a formatted message or structure, but it does not handle or incorrectly handles a length field that is inconsistent with the actual length of the associated data. |
