CVE-2026-126135Mozilla Thunderbird vulnerability
CVE-2026-126135 is a vulnerability in Mozilla Thunderbird, not yet scored.
Why this priority: Not scored yet, and no exploitation signal.
Published · Updated · NVD status: Awaiting Analysis
What it is
The record does not classify the weakness yet; the description below says what the reporter found.
How it is reached
The record does not say yet how the flaw is reached; the description below is the best guide until it is scored.
What an attacker gains
Its impact has not been scored yet.
Is it being exploited?
There is no public report of exploitation yet.
What to do
- Upgrade Mozilla Thunderbird to a fixed version for your release line (153.7, 160).
Description from NVD
If an attacker was able to perform a man-in-the-middle attack on an SMTP or POP3 server connection using STARTTLS, the attacker could inject server responses before the TLS handshake completed. Thunderbird would process these responses after the handshake, as if they had been received from the server over the encrypted connection. This could be used to make Thunderbird report a different outcome for sending or fetching mail, and to show attacker-controlled text in error messages. The encrypted connection itself was not compromised, and credentials were not exposed. Connections using SSL/TLS instead of STARTTLS were not affected. This vulnerability was fixed in Thunderbird 160 and Thunderbird 153.7.
What this means for your architecture.
A CVE names a product. Whether it matters depends on where that product sits in your systems: what reaches it, which trust boundary it guards and what it can reach once compromised. Veriom maps your components, their relationships and your trust boundaries from your code, cloud and delivery evidence, so you can see where a component like this sits. The radar itself does not look at your systems.
Components it touches
- Mozilla Thunderbird. Start from where it runs and what it is connected to.
Trust boundaries in play
Questions to answer about your own systems
- Where does Mozilla Thunderbird run in your systems, and at which version?
- Which of those instances are reachable by people you do not trust?
- What can it reach once compromised: which data stores, secrets and services?
Sources
- CVE records and CVSS scores from the NVD CVE API. This product uses the NVD API but is not endorsed or certified by the NVD.
- Exploitation status from CISA’s Known Exploited Vulnerabilities catalog.
- Exploit likelihood from FIRST’s Exploit Prediction Scoring System (EPSS), refreshed daily.
- Explanations are written by Veriom from fixed templates over each record’s data, not by a person reviewing each CVE. Descriptions are quoted from the records as published.