CVE-2021-29991
High
Description
Firefox incorrectly accepted a newline in a HTTP/3 header, interpretting it as two separate headers. This allowed for a header splitting attack against servers using HTTP/3. This vulnerability affects Firefox < 91.0.1 and Thunderbird < 91.0.1.
SeverityHigh
CVSS8.1
Exploit probability—
Product
Mozilla Firefox
PublishedNov 3, 2021
First seenNov 3, 2021
How to fix
Update
- mozilla firefox91.0.1 or later
- mozilla thunderbird91.0.1 or later
Affected products
| Product | Affected versions | Fixed in |
|---|---|---|
| mozilla firefox | v < 91.0.1 | 91.0.1 |
| mozilla thunderbird | v < 91.0.1 | 91.0.1 |
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