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Vulnerability · CVE-2026-103500

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.

Published Sep 30, 2026 · corrected/updated Oct 15, 2026 · JVN thunderbird · evidence confidence high

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.

Grounded briefings

Catalog interpretations for three audiences. Each brief cites ingested metadata and the original advisories below. They are not independent research and they do not invent exploit steps.

Executive

CVE-2026-103500 is a medium public vulnerability record for JVN thunderbird. It is not currently listed in the CISA Known Exploited catalog. Check the linked vendor or CERT advisories for patch status. This summary is a catalog interpretation of the ingested metadata and cites the original advisories below.

System administrator

Identify whether JVN thunderbird is in your estate, then compare installed versions with the affected ranges. Affected packages or ranges on record: mozilla/thunderbird. Check the linked vendor or CERT advisories for patch status. Prefer the vendor or distribution advisory linked in Sources before changing production systems. This is a catalog interpretation, not a runbook.

Security analyst

Signals on file: CVSS 6.1, EPSS 0.2%. It is not currently listed in the CISA Known Exploited catalog. Weakness classes: CWE-787. Sources contributing to this record: cve_org, epss, jvndb, mozilla. Public exploit references, when present, are outbound links only and are not proof of active exploitation. This is a catalog interpretation of stored metadata.

Exploitation and remediation

  • Exploitation evidence

    Not listed as known exploited in CISA KEV. Not in CISA KEV or VulnCheck KEV.

  • Patch and remediation

    No required-action text is stored yet. Use the vendor or CERT links in Sources for patch availability.

  • Safe detection guidance

    Compare installed versions with the affected ranges below and verify the advisory from the original publisher. This site stores metadata and outbound links only; it does not ship exploit code or proof-of-concept payloads.

Code

The project this record applies to. Exploit listings stay in References.

No public source repository is identified for this product.

Timeline

Detection, updates, and resolution for this record.

  1. Sep 30, 2026 · NIST NVD

    Detected

    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.

  2. Oct 15, 2026 · NIST NVD

    Updated

    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

  • cpe mozilla/thunderbirdversion unspecified

Sources

  • CVE.orgVulnerability recordCVE-2026-103500

    Official CVE identifier

    cve.org
  • FIRST EPSSExploitation probabilityCVE-2026-103500

    30-day exploitation probability 0.2%

    first.org
  • JVN iPediaGovernment advisoryCVE-2026-103500

    攻撃者は、ユーザーに2GB以上のサイズのメールを開かせることで、ヒープバッファオーバーフローを引き起こす可能性があります。この脆弱性は、Thunderbirdのバージョン157、140.17、および153.4で修正されています。

    jvndb.jvn.jp
  • Mozilla Security AdvisoriesVendor advisoryCVE-2026-103500

    Security Vulnerabilities fixed in Thunderbird 153.4 — Mozilla

    mozilla.org
  • NIST NVDVulnerability recordCVE-2026-103500

    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.

    nvd.nist.gov

References