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Fencer Intel
medium 6.3

CVE-2026-103500 json

Heap buffer overflow opening large email

published last mo. modified 19d ago also EUVD-2026-90200

cvss
6.3
version 3.1, CNA
cisa kev
Not listed
not in CISA's catalog
epss
0.3%
EPSS 0.3% chance of exploitation in 30 days, percentile 20%
public exploits
0
none known

Summary

An attacker could cause a heap buffer overflow by getting a user to open an email that is greater than or equal to 2GB in size. This vulnerability was fixed in Thunderbird 157, Thunderbird 140.17, and Thunderbird 153.4.

Patch / fix

  • mozilla thunderbird 140.17, 153.4
  • thunderbird Debian 12 1:140.17.0esr-1~deb12u1
  • thunderbird Debian 13 1:140.17.0esr-1~deb13u1
  • thunderbird Debian 14 1:153.4.0esr-1

debian advisories DEBIAN-CVE-2026-103500

  • MozillaThunderbird SLE Workstation Extension 15 SP7, SLE Module for Package Hub 15 SP7 153.4.0-150400.13.6.1

suse advisories SUSE-SU-2026:4627-1

  • MozillaThunderbird openSUSE Tumbleweed 153.4.0-1.1

opensuse advisories openSUSE-SU-2026:12098-1

Is CVE-2026-103500 in your stack? Fencer shows which of your repositories are affected as soon as an advisory lands, and opens the fix as a pull request.

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Vendor advisories

What the vendors themselves say about their products: affected, fixed or not affected, and what to do.

red hat product security vex CVE-2026-103500 updated cvss 8.8

thunderbird: thunderbird: Heap buffer overflow via opening large emails

  • Red Hat Enterprise Linux 8 thunderbird, thunderbird 140.14.0-1.el10_2 Red Hat Enterprise Linux 9 thunderbird, thunderbird 140.14.0-1.el10_2 Red Hat Enterprise Linux 10 thunderbird 140.14.0-1.el10_2
    not affected: vulnerable code not present

Red Hat CSAF VEX © Red Hat, Inc., from https://security.access.redhat.com/data/csaf/v2/vex/; changed: reduced to product statuses and remediations. CC BY 4.0 · csaf

CISA SSVC

Exploitation
none
Automatable
no
Technical impact
partial
Assessed
24d ago

Exploit prediction

0.28% chance of exploitation in the next 30 days, higher than 20% of all scored CVEs (FIRST EPSS, 2026-11-09).

CVSS scores

assigned by version score vector
CISA ADP 3.1 6.3 CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:L/I:L/A:L
NVD 3.1 6.1 CVSS:3.1/AV:L/AC:L/PR:N/UI:R/S:U/C:N/I:L/A:H
CNA 3.1 6.3 CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:L/I:L/A:L

Affected products

  • Mozilla Thunderbird

Classification

Weakness

References

Sources

Fencer Intel keeps one entry per vulnerability: the CVE id wins, then GHSA, and records that alias each other are merged, except that two CVEs always keep separate entries. The same data is available as JSON.

CPEs and fixed versions use Anchore's correction of NVD's data: Added CPE configurations because not yet analyzed by NVD.