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Vulnerability · NVD

CVE-2026-14899

CVE-2026-14899, high severity (CVSS 7.5): 1 tracked app concerned, all fixed or indeterminable on their current version.

Severity (CVSS): 7.5
Exploitation: 0.3 %
Tracked apps: 1
Still exposed: 0

Published on 2026-07-22

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.

Attack vector : Network No privileges required No user interaction

Show raw CVSS vector

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

EPSS 0.27% exploit very unlikely percentile 17.6%

Tracked apps referencing this CVE

For each app: the affected range, the fixing version, and where the tracked app stands today.

Mozilla Thunderbird Windows winget:Mozilla.Thunderbird

Affected <140.13.0 Fixed in 140.13.0 Latest tracked 156.0.1 patched

Observed affected builds (100)

140.0.1 140.0 139.0.2 139.0.1 139.0 138.0.2 138.0.1 138.0 137.0.2 137.0.1 137.0 136.0.1 136.0 115.14.0 115.13.0 115.12.2 115.12.1 115.11.1 115.11.0 115.10.2 115.10.1 115.10.0 115.9.0 115.8.1 115.8.0 115.7.0 115.6.1 115.6.0 115.5.2 115.5.1 +70 · see history

Vulnerable CPE configurations (1)

Vendor	Product	Platform	Versions	CPE 2.3 URI
mozilla	thunderbird All platforms (wildcard)	All platforms (wildcard)	<140.13.0	cpe:2.3:a:mozilla:thunderbird:::::esr:::*

View on NVD ↗ Advisory · www.mozilla.org

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