CVE-2026-14899
Off-by-one out of bounds read in MIME header parser for forwarding
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.
INFO
Published Date :
July 22, 2026, 8:16 p.m.
Last Modified :
July 22, 2026, 8:33 p.m.
Remotely Exploit :
No
Source :
[email protected]
Solution
- Update Thunderbird to version 153 or later.
- Apply patch for Thunderbird 140.13 if applicable.
- Restart the application after updating.
References to Advisories, Solutions, and Tools
Here, you will find a curated list of external links that provide in-depth
information, practical solutions, and valuable tools related to
CVE-2026-14899.
| URL | Resource |
|---|---|
| https://bugzilla.mozilla.org/show_bug.cgi?id=2046137 | |
| https://www.mozilla.org/security/advisories/mfsa2026-71/ | |
| https://www.mozilla.org/security/advisories/mfsa2026-72/ |
CWE - Common Weakness Enumeration
While CVE identifies
specific instances of vulnerabilities, CWE categorizes the common flaws or
weaknesses that can lead to vulnerabilities. CVE-2026-14899 is
associated with the following CWEs:
Common Attack Pattern Enumeration and Classification (CAPEC)
Common Attack Pattern Enumeration and Classification
(CAPEC)
stores attack patterns, which are descriptions of the common attributes and
approaches employed by adversaries to exploit the CVE-2026-14899
weaknesses.
We scan GitHub repositories to detect new proof-of-concept exploits. Following list is a collection of public exploits and proof-of-concepts, which have been published on GitHub (sorted by the most recently updated).
Results are limited to the first 15 repositories due to potential performance issues.
The following list is the news that have been mention
CVE-2026-14899 vulnerability anywhere in the article.
The following table lists the changes that have been made to the
CVE-2026-14899 vulnerability over time.
Vulnerability history details can be useful for understanding the evolution of a vulnerability, and for identifying the most recent changes that may impact the vulnerability's severity, exploitability, or other characteristics.
-
New CVE Received by [email protected]
Jul. 22, 2026
Action Type Old Value New Value Added Affected [{'vendor': 'Mozilla', 'product': 'Thunderbird', 'versions': [{'status': 'unaffected', 'version': '140.13', 'versionType': 'rpm', 'lessThanOrEqual': '140.*'}, {'status': 'unaffected', 'version': '153', 'versionType': 'rpm', 'lessThanOrEqual': '*'}]}] Added 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. Added Reference https://bugzilla.mozilla.org/show_bug.cgi?id=2046137 Added Reference https://www.mozilla.org/security/advisories/mfsa2026-71/ Added Reference https://www.mozilla.org/security/advisories/mfsa2026-72/