Vulnerability · Published Nov 3, 2021 · Assigned by mozilla
CVE-2021-29991
High 8.1
In plain English
A high-severity security flaw in Firefox from Mozilla. There are no confirmed reports of exploitation so far. The chance it is exploited in the next 30 days is estimated at 0.9% (higher than 60% of all known vulnerabilities). Fixed versions are available - upgrade the affected package.
Severity (CVSS NVD)8.1High
Exploit odds (30 days)0.9%top 39.9% of all CVEs
Exploited in the wildNo reportsnot in CISA KEV
Attack toolingNoneno public tooling known
Official 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.
Affected packages & fixed versions
| Ecosystem | Package | Fixed in | Advisory |
|---|---|---|---|
| Alpine:v3.20 | firefox | 92.0.1-r0 | ALPINE-CVE-2021-29991 |
| Alpine:v3.21 | firefox | 92.0.1-r0 | ALPINE-CVE-2021-29991 |
| Alpine:v3.22 | firefox | 92.0.1-r0 | ALPINE-CVE-2021-29991 |
| Alpine:v3.23 | firefox | 92.0.1-r0 | ALPINE-CVE-2021-29991 |
| Alpine:v3.21 | librewolf | 92.0.1-r0 | ALPINE-CVE-2021-29991 |
| Alpine:v3.22 | librewolf | 92.0.1-r0 | ALPINE-CVE-2021-29991 |
| Alpine:v3.23 | librewolf | 92.0.1-r0 | ALPINE-CVE-2021-29991 |
| Alpine:v3.24 | librewolf | 92.0.1-r0 | ALPINE-CVE-2021-29991 |
| Alpine:v3.20 | thunderbird | 91.3.2-r0 | ALPINE-CVE-2021-29991 |
| Alpine:v3.21 | thunderbird | 91.3.2-r0 | ALPINE-CVE-2021-29991 |
| Alpine:v3.22 | thunderbird | 91.3.2-r0 | ALPINE-CVE-2021-29991 |
| Alpine:v3.23 | thunderbird | 91.3.2-r0 | ALPINE-CVE-2021-29991 |
| Ubuntu:22.04:LTS | mozjs78 | no fix listed | UBUNTU-CVE-2021-29991 |
Affected products (as reported)
| Vendor | Product | Versions |
|---|---|---|
| Mozilla | Firefox | unspecified – before 91.0.1 |
| Mozilla | Thunderbird | unspecified – before 91.0.1 |
References
- https://www.mozilla.org/security/advisories/mfsa2021-37/ x_refsource_MISC
- https://bugzilla.mozilla.org/show_bug.cgi?id=1724896 x_refsource_MISC