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CVE-2026-14899

Off-by-one out of bounds read in MIME header parser for forwarding

Published: Jul 22, 2026Updated: Jul 27, 2026 Sources: CVE List NVDCWE-193
7.5HIGH
NVD MITRE
EPSS Score
0.3%
Top 82.5%
CISA KEV
Not in KEV
Exploits
No Known Exploits
Remediation
No Fix Available
Self-Check
OpenVAS

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.

No summary for this CVE yet.

CVSS Vector Breakdown

AV:NAC:LPR:NUI:NS:UC:HI:NA:N
Exploitability
AV:NAttack Vector
Network
AC:LAttack Complexity
Low
PR:NPrivileges Required
None
UI:NUser Interaction
None
Scope
S:UScope
Unchanged
Impact
C:HConfidentiality
High
I:NIntegrity
None
A:NAvailability
None
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Weaknesses

CWE-193

Affected Products

Mozilla
oss-project·USaka mozilla corp.
ThunderbirdOn-premDesktop App
Communications / email-server-client

Exploitability

No known exploits, KEV entries, or remediation guidance available for this vulnerability yet.
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References

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

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