HOMEVULNERABILITIESCVE-2021-3466
CRITICAL

CVE-2021-3466

CWE-120Published: March 25, 2021· Updated: Jun 17, 2026

9.8
CVSS v3.1

Official 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.

NVD Source

Technical Analysis

CVE-2021-3466 can be exploited remotely over the network without requiring physical or adjacent access, significantly expanding the attack surface for threat actors.

The vulnerability requires no privileges and no user interaction, making it a prime target for automated exploitation campaigns and worm-like propagation.

A successful exploit results in complete confidentiality breach (data exposure), full integrity compromise (data manipulation), availability disruption (denial of service), with a CVSS base score of 9.8.

CVSS v3.1 Vector Breakdown

Exploitability
Attack VectorNetwork
Attack ComplexityLow
Privileges Req.None
User InteractionNone
ScopeUnchanged
Impact
ConfidentialityHigh
IntegrityHigh
AvailabilityHigh
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H

Affected Vendors & Products

Fedora1 product(s)
fedora
gnu1 product(s)
libmicrohttpd
Red Hat1 product(s)
enterprise linux
Source: NVD CPE · 7 total CPE entries

Exploit & PoC Resources

NO KNOWN EXPLOITNo public exploit confirmed at this time
Exploit-DB
Offensive Security exploit database
GitHub PoC Search
Community PoC repositories
Rapid7 / Metasploit
Metasploit module search
PacketStorm
Security advisories & exploits
NVD Detail
Official NIST entry
MITRE CVE
CVE Program entry
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Official Patches & Advisories

PATCHhttps://bugzilla.redhat.com/show_bug.cgi?id=1939127
PATCHhttps://bugzilla.redhat.com/show_bug.cgi?id=1939127

All References (10)

→
https://bugzilla.redhat.com/show_bug.cgi?id=1939127Issue Tracking · Patch · Third Party Advisory
→
https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/4334XJNDJPYQNFE6S3S2KUJJ7TMHYCWL/
→
https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/75HDMREKITMGPGE62NP7KE62ZJVLETXN/
→
https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/K5NEPVGP3L2CZHLZ4UB44PEILHKPDBOG/
→
https://security.gentoo.org/glsa/202311-08
→
https://bugzilla.redhat.com/show_bug.cgi?id=1939127Issue Tracking · Patch · Third Party Advisory
→
https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/4334XJNDJPYQNFE6S3S2KUJJ7TMHYCWL/
→
https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/75HDMREKITMGPGE62NP7KE62ZJVLETXN/
→
https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/K5NEPVGP3L2CZHLZ4UB44PEILHKPDBOG/
→
https://security.gentoo.org/glsa/202311-08

Quick Facts

CVE IDCVE-2021-3466
CVSS Score9.8 / 10
SeverityCRITICAL
WeaknessCWE-120
CISA KEVNo
Affected3 vendor(s)
PublishedMar 25, 2021

Related CVEs (CWE-120)

CVE-2012-10035
10.0
CVE-2007-1770
10.0
CVE-2026-24823
10.0
CVE-2026-24800
10.0
CVE-1999-0046
10.0
CVE-1999-1237
10.0

Recommended Actions

  • →Apply vendor patches immediately
  • →Monitor CVE-2021-3466 in threat intel feeds
  • →Review IDS/IPS signatures for exploitation attempts
Data sourced from NVD (NIST), CISA KEV, and EPSS (FIRST). Analysis generated by CTIWatch. CVE data is provided under the NVD usage policy.
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