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Vulnerability record · CVE-2026-14899 · published 22 July 2026

CVE-2026-14899: Mozilla thunderbird vulnerability

Mozilla · Thunderbird

The code to parse MIME headers for display when forwarding a message (if the setting to view all headers was enabled) had an off-by-one error, allowing a single byte to be read from the memory after the buffer for the headers, and potentially crashing Thunderbird. This vulnerability was fixed in Thunderbird 153 and Thunderbird 140.13.

7.5 CVSS 3.1 High EPSS 0.27% · top 82.3% CWE-193 · CWE-193
7.5CVSS 3.1 base score
0.27%EPSS exploitation probability, 30 days
NoNot in CISA KEV
1Affected product versions listed by NVD
3References
12 Aug 2026Last modified by NVD

Description

The code to parse MIME headers for display when forwarding a message (if the setting to view all headers was enabled) had an off-by-one error, allowing a single byte to be read from the memory after the buffer for the headers, and potentially crashing Thunderbird. This vulnerability was fixed in Thunderbird 153 and Thunderbird 140.13.

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N

Affected products

1 vulnerable configurations from NVD's CPE data, grouped by vendor and product.

References

LinkTags
https://bugzilla.mozilla.org/show_bug.cgi?id=2046137 Permissions Required
https://www.mozilla.org/security/advisories/mfsa2026-71/ Vendor Advisory
https://www.mozilla.org/security/advisories/mfsa2026-72/ Vendor Advisory

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Related vulnerabilities

Same products first, then exploited flaws of the same weakness class.

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Source: NIST National Vulnerability Database (record CVE-2026-14899), CISA KEV, FIRST EPSS (scores of 2026-09-26). This page is refreshed as NVD updates the record.