CVE-2021-3466: A flaw was found in libmicrohttpd. A missing bounds check in the post_process_urlencoded function leads to a buffer overflow, allowing a remote attack...

Description

A flaw was found in libmicrohttpd. A missing bounds check in the post_process_urlencoded function leads to a buffer overflow, allowing a remote attacker to write arbitrary data in an application that uses libmicrohttpd. The highest threat from this vulnerability is to data confidentiality and integrity as well as system availability. Only version 0.9.70 is vulnerable.

Metrics

CVSS 3.1

9.8/10

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

EPSS Probability

8.74%

94.5th percentile

Probability of exploitation in the next 30 days. Learn more

Weakness Enumeration

CWE-120

Affected Software

Vendor	Product	Versions
Gnu	Libmicrohttpd	0.9.70
Redhat	Enterprise Linux	6.0
Redhat	Enterprise Linux	7.0
Redhat	Enterprise Linux	8.0
Fedoraproject	Fedora	32
Fedoraproject	Fedora	33
Fedoraproject	Fedora	34

References

Timeline

Published: Mar 25, 2021
Last Modified: Jun 17, 2026
Status: Modified

Frequently Asked Questions

What is CVE-2021-3466?

A flaw was found in libmicrohttpd. A missing bounds check in the post_process_urlencoded function leads to a buffer overflow, allowing a remote attacker to write arbitrary data in an application that uses libmicrohttpd. The highest threat from this vulnerability is to data confidentiality and integrity as well as system availability. Only version 0.9.70 is vulnerable.

How severe is CVE-2021-3466?

CVE-2021-3466 has a CVSS score of 9.8/10 (CRITICAL severity). The EPSS model estimates a 8.74% probability of exploitation in the next 30 days.

How do I fix CVE-2021-3466?

Check the vendor references and advisories linked above for patched versions and mitigation guidance. You can also run a Strix scan to test if your systems are affected.