Vulnerability 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.
CVSS Score
HIGH
Affected Products
| Vendor | Product | Versions |
|---|---|---|
| Mozilla | Firefox | < 91.0.1 |
| Mozilla | Thunderbird | < 91.0.1 |
Related Weaknesses (CWE)
References
- https://bugzilla.mozilla.org/show_bug.cgi?id=1724896Permissions Required
- https://www.mozilla.org/security/advisories/mfsa2021-37/Vendor Advisory
- https://bugzilla.mozilla.org/show_bug.cgi?id=1724896Permissions Required
- https://www.mozilla.org/security/advisories/mfsa2021-37/Vendor Advisory
FAQ
What is CVE-2021-29991?
CVE-2021-29991 is a vulnerability with a CVSS score of 8.1 (HIGH). 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...
How severe is CVE-2021-29991?
CVE-2021-29991 has been rated HIGH with a CVSS base score of 8.1/10. Review the CVSS metrics above for detailed severity breakdown.
Is there a patch for CVE-2021-29991?
Check the references section above for vendor advisories and patch information. Affected products include: Mozilla Firefox, Mozilla Thunderbird.