CVE-2021-4126
Reported by mozilla · Published December 22, 2022
When receiving an OpenPGP/MIME signed email message that contains an additional outer MIME message layer, for example a message footer added by a mailing list gateway, Thunderbird only considered the inner signed message for the signature validity. This gave the false impression that the additional contents were also covered by the digital signature. Starting with Thunderbird version 91.4.1, only the signature that belongs to the top level MIME part will be considered for the displayed status. This vulnerability affects Thunderbird < 91.4.1.
Fixed versions
Upgrade to a fixed version or later. Language registries are listed first, then Linux distributions, then vendor products.
| Package | Ecosystem | Fixed in |
|---|---|---|
| thunderbird | Alpine | 91.4.1-r0 |
| Thunderbird | Mozilla | 91.4.1 |
Risk scores
Affected products
| Vendor | Product | Versions |
|---|---|---|
| Mozilla | Thunderbird | unspecified |
| Mozilla | Thunderbird | * |
| alpine | thunderbird | 0 |
Timeline
- Dec 21, 2021 CVE Published
- Dec 23, 2022 EPSS Score (30 in total, the first dated here)
- Apr 3, 2026 Security Advisory (2 in total, the first dated here)
- Jul 20, 2026 Coalition ESS Score
Query this with the API
The same record, from the CLI:
vulnetix vdb vuln CVE-2021-4126
vulnetix vdb fixes CVE-2021-4126Or with curl, using the org id and key from your account page:
curl -s -H "Authorization: ApiKey ${VULNETIX_ORG_ID}:${VULNETIX_API_KEY}" \
"https://api.vdb.vulnetix.com/v2/vuln/CVE-2021-4126/fixes/registry"The Community plan is free and allows 50 queries a day. Get a free API key · API quickstart