CVE-2021-3181

rfc822.c in Mutt through 2.0.4 allows remote attackers to cause a denial of service (mailbox unavailability) by sending email messages with sequences of semicolon characters in RFC822 address fields (aka terminators of empty groups). A small email message from the attacker can cause large memory consumption, and the victim may then be unable to see email messages from other persons.

Published: 2021-01-19 Last update: 2024-11-21 Assigner: [email protected] Source: [email protected]
NVD Status：Modified，CVE State: published
View at NVD, CVE.org, EUVD

CVE-2021-3181 is rated Moderate Risk (56/100): CVSS Medium severity, with medium exploitation likelihood (EPSS 2.80%). Review affected assets and schedule remediation.

Risk is dynamic; we continuously reassess and refresh what is shown on this page as upstream context changes.

Exploit prediction scoring system (EPSS) score for CVE-2021-3181

EPSS lead: Daily EPSS estimates relative likelihood of exploitation; percentile ranks this CVE among scored vulnerabilities (higher = more severe relative rank).

# Date Old EPSS score New EPSS score Delta (New - Old)
1 2026-05-28 3.00% 2.80% -0.20%
2 2025-12-28 2.54% 3.00% +0.46%
3 2025-12-27 — 2.54% —

Full EPSS history (25 records total)

Common vulnerability scoring system (CVSS) metrics for CVE-2021-3181

CVSS metrics for this CVE.

Base score Version Severity Vector Exploitability Impact Score source
6.5 3.1 MEDIUM
CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:N/A:H Click to expand
Attack vector (AV:N)
Could be attacked over the internet or any normal routed network—not just someone sitting at the machine.
Attack complexity (AC:L)
Once they can reach the bug, pulling it off is straightforward—no weird race conditions or rare setup.
Privileges required (PR:N)
No account or special rights needed—anonymous or random user is enough.
User interaction (UI:R)
A real person has to do something—click, install, enable—otherwise it doesn’t land.
Scope (S:U)
Damage stays in the same “trust bubble” as the broken component—no big spill into unrelated systems.
Confidentiality (C:N)
Doesn’t really leak secrets in a meaningful way.
Integrity (I:N)
Data isn’t meaningfully altered or forged.
Availability (A:H)
Could take the service down hard or make it unusable for people who depend on it.
 2.8 3.6 [email protected]
4.3 2.0 MEDIUM
AV:N/AC:M/Au:N/C:N/I:N/A:P Click to expand
Access vector (AV:N)
Can be exploited remotely over network reachability.
Access complexity (AC:M)
Exploitation needs some favorable conditions, but not exceptional ones.
Authentication (AU:N)
No authentication is required.
Confidentiality impact (C:N)
No confidentiality impact.
Integrity impact (I:N)
No integrity impact.
Availability impact (A:P)
Partial availability impact.
 8.6 2.9 [email protected]

Weakness enumeration for CVE-2021-3181

OS Trackers for CVE-2021-3181

vendor priority summary link
alpine medium CVE-2021-3181: 1 source package rows (mutt); 11 state rows across 7 repos (3.17-community, 3.18-community, 3.19-community, 3.20-community, 3.21-community, 3.22-community, edge-community); fixed 7, open 4. https://security.alpinelinux.org/vuln/CVE-2021-3181
debian not yet assigned CVE-2021-3181 not yet assigned priority: Debian including 1 source packages (mutt), 5 status rows across 5 suites (bookworm, bullseye, forky, sid, trixie): resolved 5. https://security-tracker.debian.org/tracker/CVE-2021-3181
gentoo normal CVE-2021-3181: 1 GLSA(s) (202101-25), 1 atom(s) (mail-client/mutt); latest impact normal. https://bugs.gentoo.org/buglist.cgi?quicksearch=CVE-2021-3181
redhat medium — https://access.redhat.com/security/cve/CVE-2021-3181
suse medium — https://www.suse.com/security/cve/CVE-2021-3181/
ubuntu medium CVE-2021-3181 medium priority: Ubuntu including 1 source packages (mutt), 6 status rows across 6 suites (bionic, focal, groovy, trusty, upstream, xenial): released 4, DNE 1, needs-triage 1. https://ubuntu.com/security/CVE-2021-3181

Affected software / configurations for CVE-2021-3181

Vendor Product Version Raw CPE
mutt mutt <= 2.0.4 cpe:2.3:a:mutt:mutt:*:*:*:*:*:*:*:*
debian debian_linux 9.0 cpe:2.3:o:debian:debian_linux:9.0:*:*:*:*:*:*:*
debian debian_linux 10.0 cpe:2.3:o:debian:debian_linux:10.0:*:*:*:*:*:*:*
fedoraproject fedora 32 cpe:2.3:o:fedoraproject:fedora:32:*:*:*:*:*:*:*
fedoraproject fedora 33 cpe:2.3:o:fedoraproject:fedora:33:*:*:*:*:*:*:*

References for CVE-2021-3181

URL Tags
http://www.openwall.com/lists/oss-security/2021/01/19/10 Mailing List Third Party Advisory
http://www.openwall.com/lists/oss-security/2021/01/27/3 Mailing List Third Party Advisory
https://gitlab.com/muttmua/mutt/-/commit/4a2becbdb4422aaffe3ce314991b9d670b7adf17 Patch Third Party Advisory
https://gitlab.com/muttmua/mutt/-/commit/939b02b33ae29bc0d642570c1dcfd4b339037d19 Patch Third Party Advisory
https://gitlab.com/muttmua/mutt/-/commit/d4305208955c5cdd9fe96dfa61e7c1e14e176a14 Patch Third Party Advisory
https://gitlab.com/muttmua/mutt/-/issues/323 Third Party Advisory
https://lists.debian.org/debian-lts-announce/2021/01/msg00017.html Mailing List Third Party Advisory
https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/DXGWXFO77HBCD3VYEIYHHYU33LYWWWNQ/
https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/P2OMLQKAOHPYQA4GI7ZUO6UKCPUHLYO7/
https://security.gentoo.org/glsa/202101-25 Third Party Advisory
https://www.debian.org/security/2021/dsa-4838 Third Party Advisory
cvelogic Threat Intelligence