CVE-2021-29946

HighCVSS 8.8/10Last modified Jun 17, 2026

Description

Ports that were written as an integer overflow above the bounds of a 16-bit integer could have bypassed port blocking restrictions when used in the Alt-Svc header. This vulnerability affects Firefox ESR < 78.10, Thunderbird < 78.10, and Firefox < 88.

Metrics

CVSS 3.1 8.8/10CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H

Weakness enumeration

CWE-190

Affected software

Vendor	Product	Versions
Mozilla	Firefox ESR	>= unspecified, < 78.10
Mozilla	Thunderbird	>= unspecified, < 78.10
Mozilla	Firefox	>= unspecified, < 88

References

https://bugzilla.mozilla.org/show_bug.cgi?id=1698503Permissions Required, Vendor Advisory
https://www.mozilla.org/security/advisories/mfsa2021-14/Release Notes, Vendor Advisory
https://www.mozilla.org/security/advisories/mfsa2021-15/Release Notes, Vendor Advisory
https://www.mozilla.org/security/advisories/mfsa2021-16/Release Notes, Vendor Advisory
https://bugzilla.mozilla.org/show_bug.cgi?id=1698503Permissions Required, Vendor Advisory
https://www.mozilla.org/security/advisories/mfsa2021-14/Release Notes, Vendor Advisory
https://www.mozilla.org/security/advisories/mfsa2021-15/Release Notes, Vendor Advisory
https://www.mozilla.org/security/advisories/mfsa2021-16/Release Notes, Vendor Advisory

Timeline

Published: Jun 24, 2021
Last modified: Jun 17, 2026
NVD status: Modified

Related CVEs from 2021

CVE-2021-299478.8Mozilla developers and community members reported memory safety bugs present in Firefox 87. Some of these bugs showed evidence of memory cor CVE-2021-299482.5Signatures are written to disk before and read during verification, which might be subject to a race condition when a malicious local proces CVE-2021-299497.8When loading the shared library that provides the OTR protocol implementation, Thunderbird will initially attempt to open it using a filenam CVE-2021-299507.5Thunderbird unprotects a secret OpenPGP key prior to using it for a decryption, signing or key import task. If the task runs into a failure,CVE-2021-299516.5The Mozilla Maintenance Service granted SERVICE_START access to BUILTIN|Users which, in a domain network, grants normal remote users access CVE-2021-299527.5When Web Render components were destructed, a race condition could have caused undefined behavior, and we presume that with enough effort ma CVE-2021-299536.1A malicious webpage could have forced a Firefox for Android user into executing attacker-controlled JavaScript in the context of another dom CVE-2021-299549.8Proxy functionality built into Hubs Cloud’s Reticulum software allowed access to internal URLs, including the metadata service. This vulnera CVE-2021-299555.3A transient execution vulnerability, named Floating Point Value Injection (FPVI) allowed an attacker to leak arbitrary memory addresses and CVE-2021-299564.3OpenPGP secret keys that were imported using Thunderbird version 78.8.1 up to version 78.10.1 were stored unencrypted on the user's local di CVE-2021-299574.3If a MIME encoded email contains an OpenPGP inline signed or encrypted message part, but also contains an additional unprotected part, Thund CVE-2021-299584.3When a download was initiated, the client did not check whether it was in normal or private browsing mode, which led to private mode cookies