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 · catalog updated Oct 15, 2026 · JVN
Check if you run it
No confirmed exploitation is on record for CVE-2026-103500. EPSS is 0.21%. Act only if a listed version of JVN is installed.
Gaps on this record
- No version range is stored. A customer cannot check an installed version against this record.
- No vendor fix or required action is stored. Compare the linked advisory before you change production.
- Severity
- Medium6.1
- Known exploitation
- Not in CISA/VulnCheck KEV
- EPSS
- 0.21%
- Remediation
- Advisory link
- Affected products
- cpe mozilla/thunderbird
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.
Are you affected?
Enter the version you run. The result uses only the ranges stored on this record.
The check returns affected, not affected, or incomplete. It does not guess a version that is missing from the record.
- cpe mozilla/thunderbirdversion unspecified
How to fix CVE-2026-103500
Recommended remediation
A patch or advisory reference is linked. Open the original publisher for availability by product version.
Official advisories
What to do
Three questions, each answered from this record only. Confirm the vendor advisory before you patch.
Should you patch?
No confirmed exploitation is on record for CVE-2026-103500. EPSS is 0.21%. Act only if a listed version of JVN is installed.
Which versions are affected?
Affected version ranges are not on this record. Compare the installed version with the linked vendor advisory before you change production.
What should an analyst verify?
CWE-787: Out-of-bounds Write. EPSS 0.21%. There is no CISA KEV listing. No Exploit-DB or Metasploit reference is linked. Use the source links for the original advisory.
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.
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.
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.
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
Freshness
Last verified in this catalog Oct 18, 2026. Significant claims (KEV, EPSS, CVSS, affected ranges) come from the source rows above — open the original publisher for the authoritative advisory.