Reference page — cumulative record through Monday, October 19, 2026 UTC. Reference pages update as the archive grows; only dated daily editions are immutable pages of record.

CVE-2026-103500

CVE-2026-103500MEDIUM

Mozilla Thunderbird — Heap buffer overflow opening large email

  AV  AC  PR  UI  S  C  I  A   CVSS    EPSS   %ile   KEV
   L   L   N   R  U  N  L  H    6.1   .0021   11.0     —

AFFECTED
  Product      Versions     Fixed
  Thunderbird  unspecified  140.17

TIMELINE
  Sep 30  Reserved by mozilla
  Sep 30  Published (CNA: mozilla)
  Oct 15  ENRICHED — CVE-2026-103500 (Mozilla Thunderbird). Received CVSS 6.1 and CPE data from NVD.

CWE-787, CWE-122 · CNA: mozilla · CVSS v3.1 · 4 references · NVD status: Modified

Description

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.

Lifecycle

Complete event history — 3 events, chronological
Date	Event	Detail
September 30, 2026	Reserved	Reserved by mozilla
September 30, 2026	Published	Published (CNA: mozilla)
October 15, 2026	ENRICHED	ENRICHED — CVE-2026-103500 (Mozilla Thunderbird). Received CVSS 6.1 and CPE data from NVD.

Affected

Affected products and packages — 1 row
Vendor	Product / Package	Ecosystem	Version introduced	Fixed
Mozilla	Thunderbird	—	—	140.17

Weaknesses

CWE-787 · CWE-122

References (4)

https://bugzilla.mozilla.org/show_bug.cgi?id=2070267 [Permissions Required]
https://www.mozilla.org/security/advisories/mfsa2026-101/ [Vendor Advisory]
https://www.mozilla.org/security/advisories/mfsa2026-102/ [Vendor Advisory]
https://www.mozilla.org/security/advisories/mfsa2026-103/ [Vendor Advisory]

Authoritative record: CVE-2026-103500 at cve.org

Vendors: mozilla

Weaknesses: CWE-787 · CWE-122

About this page

This is a reference page, not a dated page of record. It assembles the complete lifecycle of CVE-2026-103500 from the CVE Program record, NVD enrichment, the CISA KEV catalog, EPSS, and OSV advisories. The box score's numbers (CVSS, EPSS, KEV status) are current as of Monday, October 19, 2026 UTC and are re-derived as the archive grows; only dated daily editions are immutable pages of record. The authoritative source for this identifier is cve.org.