---
id: CVE-2026-110247
title: >-
  Several buffer-growth sites in libmime performed size arithmetic in 32-bit
  types without overflow checks
summary: >-
  Several buffer-growth sites in libmime performed size arithmetic in 32-bit
  types without overflow checks. On a sufficiently large message the growth
  guard could fail open, or the buffer could be reallocated smaller than
  required, and a s…
severity: high
published: '2026-10-13'
updated: '2026-10-13'
sourceUpdated: '2026-10-13T19:30:29.797'
source: NVD
sourceUrl: 'https://nvd.nist.gov/vuln/detail/CVE-2026-110247'
references:
  - url: 'https://bugzilla.mozilla.org/show_bug.cgi?id=2071621'
    label: security@mozilla.org
  - url: 'https://www.mozilla.org/security/advisories/mfsa2026-109/'
    label: security@mozilla.org
  - url: >-
      https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-110247.json
  - url: 'https://access.redhat.com/security/cve/CVE-2026-110247'
  - url: 'https://bugzilla.redhat.com/show_bug.cgi?id=2550753'
  - url: 'https://www.cve.org/CVERecord?id=CVE-2026-110247'
  - url: 'https://nvd.nist.gov/vuln/detail/CVE-2026-110247'
tags:
  - nvd
  - csaf
  - vex
  - red-hat
  - cve.org
ingestedAt: '2026-10-13T19:43:28.944Z'
vendor: Red Hat
product: Red Hat Enterprise Linux 10
affected:
  - enterprise_linux 10
  - enterprise_linux 8
  - enterprise_linux 9
cvss: 8.8
cvssVector: 'CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H'
cvssSource: vendor
cwe:
  - CWE-787
---

## Overview

Several buffer-growth sites in libmime performed size arithmetic in 32-bit types without overflow checks. On a sufficiently large message the growth guard could fail open, or the buffer could be reallocated smaller than required, and a subsequent memcpy would then write attacker-controlled data across adjacent heap allocations. This vulnerability was fixed in Thunderbird 158.

## Remediation

Refer to the linked advisories for vendor-supplied fixes and affected version ranges.

## 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 2026-10-13 · [vex](https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-110247.json)