Multiple vulnerabilities in Mozilla Thunderbird (July 2, 2026)

unknownCVE-2026-57963 CVE-2026-57962

Multiple vulnerabilities have been discovered in Mozilla Thunderbird. They allow an attacker to cause a breach of data integrity and a denial of service.

CSIRTS triage

vendor: Mozilla product: Thunderbird Denial of serviceOther

What: Multiple vulnerabilities allow an attacker to cause a breach of data integrity and a denial of service.
Who is affected: Users of Mozilla Thunderbird.
Urgency: Remediation is important due to the potential for data integrity issues and denial of service, with unknown exploitation status.
Action: Update to the latest version of Mozilla Thunderbird.

AI-assisted analysis generated from the source advisory — verify against the original.

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Details

Source: CERT-FR Avis de sécurité (FR · national-cert · site)
Severity: unknown
Published: 2026-07-02
Exploitation: Not in CISA KEV at last sync
Language: Machine-translated to English — verify against the original

Original advisory: https://www.cert.ssi.gouv.fr/avis/CERTFR-2026-AVI-0827/

Exploitation outlook

EPSS (FIRST.org) estimates each CVE’s probability of exploitation in the next 30 days — here is the CSIRTS.com read on those numbers.

Low exploitation riskCVE-2026-579630.19% 30-day exploitation probability — currently an unlikely target, but scores change as exploit code circulates. Riskier than 9% of all EPSS-scored CVEs.
Low exploitation riskCVE-2026-579620.22% 30-day exploitation probability — currently an unlikely target, but scores change as exploit code circulates. Riskier than 12% of all EPSS-scored CVEs.

Referenced CVEs

CVE	CSIRTS overview	External
CVE-2026-57963	coverage & exploitation status	NVD · CVE.org
CVE-2026-57962	coverage & exploitation status	NVD · CVE.org

Same CVEs, other sources

How other CERTs, PSIRTs and databases cover the vulnerabilities in this advisory.

Recent advisories for Mozilla Thunderbird

A cluster of recent advisories against the same product widens the attack surface — attackers routinely chain freshly published CVEs on one product, so review these together.

high[NEW] [high] Mozilla Firefox, Firefox ESR and Thunderbird: Multiple Vulnerabilitiescert-bund · 2026-08-25
medium[UPDATE] [medium] Mozilla Thunderbird: Multiple vulnerabilitiescert-bund · 2026-08-18
high[UPDATE] [high] Mozilla Firefox, Firefox ESR and Thunderbird: Multiple vulnerabilitiescert-bund · 2026-08-17
unknownMultiple vulnerabilities in Mozilla Thunderbird (July 23, 2026)cert-fr-avis · 2026-07-23
high[UPDATE] [high] Mozilla Thunderbird, Firefox ESR and Firefox: Multiple vulnerabilitiescert-bund · 2026-07-22
high[UPDATE] [high] Mozilla Firefox and Thunderbird: Multiple vulnerabilitiescert-bund · 2026-07-21