CVE-2026-14899

⚠️ high

Summary

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 Score

7.5

High

EPSS Score

0.3

Exploit Probability

Published Date

2026-07-22

First Seen: 2026-07-23

📊 Relative Risk Intelligence

This CVE is Moderate Risk - more severe than 68.0% of all 349,016 vulnerabilities in our database.

#111,749

Above average severity

Severity Percentile

🎯 CISA SSVC Assessment Updated: Jul 27, 2026

🔍 Exploitation Status

None

No known exploits

⚙️ Automatable

YES

Can be exploited automatically

💥 Technical Impact

Partial

Limited system impact

🏆 Discovered By

Claude, Kai Engert

SSVC data provided by CISA

Last Modified 2026-08-12

Source NVD 🔗

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

CWE IDs (Weakness Types)

CWE-193

📦 Affected Products 1

Vendor	Product	Status	Affected Versions
mozilla	thunderbird	Affected	< 140.13.0

🔗 References 3

https://bugzilla.mozilla.org/show_bug.cgi?id=2046137

Permissions Required

https://www.mozilla.org/security/advisories/mfsa2026...

Vendor Advisory

https://www.mozilla.org/security/advisories/mfsa2026...

Vendor Advisory

🔗 Related CVEs 6

CVE ID	Severity	CVSS	EPSS	Summary	Published
CVE-2026-74934	⚠️ high	7.5	0.2	Site isolation issue in the Graphics: CanvasWebGL component. This vulnerability was fixed in Firefox 154, Firefox ESR 11...	2026-08-18
CVE-2026-74935	⚠️ high	8.8	0.3	Privilege escalation in the DOM: Networking component. This vulnerability was fixed in Firefox 154, Firefox ESR 115.39, ...	2026-08-18
CVE-2026-74936	⛔ critical	9.8	0.4	Use-after-free in the JavaScript: WebAssembly component. This vulnerability was fixed in Firefox 154, Firefox ESR 140.14...	2026-08-18
CVE-2026-74937	⚠️ high	8.8	0.3	Use-after-free in the JavaScript: GC component. This vulnerability was fixed in Firefox 154, Firefox ESR 153.1, Thunderb...	2026-08-18
CVE-2026-74938	⛔ critical	9.1	0.3	Mitigation bypass in the JavaScript: GC component. This vulnerability was fixed in Firefox 154, Firefox ESR 153.1, Thund...	2026-08-18
CVE-2026-74939	⚠️ high	8.8	0.3	Privilege escalation in the DOM: Navigation component. This vulnerability was fixed in Firefox 154, Firefox ESR 115.39, ...	2026-08-18

These CVEs affect the same products