---
id: CVE-2026-103500
title: >-
  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
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.
severity: medium
cvss: 6.1
cvssVector: 'CVSS:3.1/AV:L/AC:L/PR:N/UI:R/S:U/C:N/I:L/A:H'
cwe:
  - CWE-787
  - CWE-122
vendor: mozilla
product: thunderbird
affected:
  - thunderbird < 140.17.0
  - 'thunderbird >= 141.0, < 153.4.0'
  - 'thunderbird >= 154.0, < 157.0'
patched:
  - thunderbird 157.0
published: '2026-09-30'
updated: '2026-10-16'
sourceUpdated: '2026-10-16T19:17:01.550'
source: NVD
sourceUrl: 'https://nvd.nist.gov/vuln/detail/CVE-2026-103500'
references:
  - url: 'https://bugzilla.mozilla.org/show_bug.cgi?id=2070267'
    label: security@mozilla.org
  - url: 'https://www.mozilla.org/security/advisories/mfsa2026-101/'
    label: security@mozilla.org
  - url: 'https://www.mozilla.org/security/advisories/mfsa2026-102/'
    label: security@mozilla.org
  - url: 'https://www.mozilla.org/security/advisories/mfsa2026-103/'
    label: security@mozilla.org
  - url: >-
      https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-103500.json
  - url: 'https://access.redhat.com/security/cve/CVE-2026-103500'
  - url: 'https://bugzilla.redhat.com/show_bug.cgi?id=2544154'
  - url: 'https://www.cve.org/CVERecord?id=CVE-2026-103500'
  - url: 'https://nvd.nist.gov/vuln/detail/CVE-2026-103500'
tags:
  - nvd
  - cve.org
  - csaf
  - vex
  - red-hat
  - score-dispute
epss: 0.00277
epssPercentile: 0.20021
ssvc:
  exploitation: none
  automatable: 'no'
  technicalImpact: partial
  timestamp: '2026-10-16T18:33:49.871087Z'
scores:
  nvd: 6.1
  vendor: 8.8
  adp: 6.3
ingestedAt: '2026-09-30T18:17:24.565Z'
---

## Overview

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.

## Affected

- `thunderbird < 140.17.0`
- `thunderbird >= 141.0, < 153.4.0`
- `thunderbird >= 154.0, < 157.0`

## Remediation

Upgrade past the affected range:

- `thunderbird 157.0`

## Vendor advisories

- **Red Hat VEX** · Important · affected: Red Hat Enterprise Linux 10, Red Hat Enterprise Linux 8, Red Hat Enterprise Linux 9 · no fix planned: Red Hat Enterprise Linux 10, Red Hat Enterprise Linux 8, Red Hat Enterprise Linux 9 · updated 2026-10-16 · [vex](https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-103500.json)