What is CVE-2021-3181?

CVE-2021-3181 is a medium-severity vulnerability in Mutt, classified under Missing Release of Memory after Effective Lifetime. CVSS score: 6.5/10. Published 2021-01-19.

How severe is CVE-2021-3181?

Medium severity. CVSS v3 base score is 6.5 out of 10.

Vulnerability in Mutt

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 modified 2026-06-17.

CVSS v3 metric

CVSS v3 base score 6.5 (Medium). Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:N/A:H.

EPSS exploit prediction

EPSS: 0.028 (86.4th percentile), scored 2026-10-19.

Low probability of exploitation in the next 30 days, but still tracked. 86th percentile — 86.4% of CVEs in the catalogue have a lower EPSS than this one. How to read EPSS.

EPSS over last 30 days · oldest: 0.028 · newest: 0.028 · change: +0.000

Affected products

Mutt
Debian Linux — versions 9.0, 10.0
Fedoraproject Fedora — versions 32, 33

Weakness classification (CWE)

CWE-401 — Missing Release of Memory after Effective Lifetime

References

gitlab.com/muttmua/mutt/-/issues/323 (Third Party Advisory)
gitlab.com/muttmua/mutt/-/commit/4a2becbdb4422aaffe3ce314991b9d670b7adf17 (Patch, Third Party Advisory)
gitlab.com/muttmua/mutt/-/commit/939b02b33ae29bc0d642570c1dcfd4b339037d19 (Patch, Third Party Advisory)
gitlab.com/muttmua/mutt/-/commit/d4305208955c5cdd9fe96dfa61e7c1e14e176a14 (Patch, Third Party Advisory)
www.openwall.com/lists/oss-security/2021/01/19/10 (mailing-list, Mailing List, Third Party Advisory)
lists.debian.org/debian-lts-announce/2021/01/msg00017.html (mailing-list, Mailing List, Third Party Advisory)
security.gentoo.org/glsa/202101-25 (vendor-advisory, Third Party Advisory)
www.debian.org/security/2021/dsa-4838 (vendor-advisory, Third Party Advisory)
www.openwall.com/lists/oss-security/2021/01/27/3 (mailing-list, Mailing List, Third Party Advisory)
lists.fedoraproject.org/archives/list/package-announce@lists.fedoraproject.org/… (vendor-advisory)

Frequently asked questions

What is CVE-2021-3181?: CVE-2021-3181 is a medium-severity vulnerability in Mutt, classified under Missing Release of Memory after Effective Lifetime. CVSS score: 6.5/10. Published 2021-01-19.
How severe is CVE-2021-3181?: Medium severity. CVSS v3 base score is 6.5 out of 10.