CVE-2021-33515

The submission service in Dovecot before 2.3.15 allows STARTTLS command injection in lib-smtp. Sensitive information can be redirected to an attacker-controlled address.

Published: 2021-06-28 Last update: 2024-11-21 Assigner: [email protected] Source: [email protected]
NVD Status：Modified，CVE State: published
View at NVD, CVE.org, EUVD

CVE-2021-33515 is rated Moderate Risk (45.9/100): CVSS Medium severity, with high exploitation likelihood (EPSS 5.86%, 91th percentile). EPSS ranks this CVE among the most likely to be exploited in the near term. High exploitation likelihood—assess exposure and prioritize 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-2021-33515

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 2026-04-05 11.35% 5.86% -5.49%
2 2026-04-03 9.84% 11.35% +1.51%
3 2026-03-12 — 9.84% —

Full EPSS history (56 records total)

Common vulnerability scoring system (CVSS) metrics for CVE-2021-33515

CVSS metrics for this CVE.

Base score Version Severity Vector Exploitability Impact Score source
4.8 3.1 MEDIUM
CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:L/I:L/A:N 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:H)
Even with access, the exploit needs extra luck, timing, or a fussy environment to actually work.
Privileges required (PR:N)
No account or special rights needed—anonymous or random user is enough.
User interaction (UI:N)
Nobody has to click “OK” or open a trap file; it can work without a victim helping.
Scope (S:U)
Damage stays in the same “trust bubble” as the broken component—no big spill into unrelated systems.
Confidentiality (C:L)
Some sensitive info could get out, but not a total data dump.
Integrity (I:L)
Attackers could change some data, but it’s limited—not everything goes.
Availability (A:N)
Service keeps running; no real outage angle.
 2.2 2.5 [email protected]
5.8 2.0 MEDIUM
AV:N/AC:M/Au:N/C:P/I:P/A:N 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:P)
Partial confidentiality impact.
Integrity impact (I:P)
Partial integrity impact.
Availability impact (A:N)
No availability impact.
 8.6 4.9 [email protected]

Weakness enumeration for CVE-2021-33515

OS Trackers for CVE-2021-33515

vendor priority summary link
alpine medium CVE-2021-33515: 1 source package rows (dovecot); 59 state rows across 9 repos (3.11-main, 3.12-main, 3.17-main, 3.18-main, 3.19-main, 3.20-main, 3.21-main, 3.22-main, edge-main); fixed 9, open 50. https://security.alpinelinux.org/vuln/CVE-2021-33515
debian not yet assigned CVE-2021-33515 not yet assigned priority: Debian including 1 source packages (dovecot), 5 status rows across 5 suites (bookworm, bullseye, forky, sid, trixie): resolved 5. https://security-tracker.debian.org/tracker/CVE-2021-33515
gentoo low CVE-2021-33515: 1 GLSA(s) (202107-41), 1 atom(s) (net-mail/dovecot); latest impact low. https://bugs.gentoo.org/buglist.cgi?quicksearch=CVE-2021-33515
redhat medium — https://access.redhat.com/security/cve/CVE-2021-33515
suse medium CVE-2021-33515 severity moderate: SUSE including 70 source package names (dovecot, dovecot-2.3.16-2.el8, …), 323 product×package rows across 53 product lines (HPE Helion OpenStack 8, SUSE CaaS Platform 4.0, … (53 product lines)): Fixed 227, Known Not Affected 96. https://www.suse.com/security/cve/CVE-2021-33515/
ubuntu medium CVE-2021-33515 medium priority: Ubuntu including 1 source packages (dovecot), 9 status rows across 9 suites (bionic, focal, groovy, hirsute, impish, jammy, trusty, upstream, xenial): released 6, not-affected 3. https://ubuntu.com/security/CVE-2021-33515

Affected software / configurations for CVE-2021-33515

Vendor Product Version Raw CPE
dovecot dovecot < 2.3.14.1 cpe:2.3:a:dovecot:dovecot:*:*:*:*:*:*:*:*
fedoraproject fedora 33 cpe:2.3:o:fedoraproject:fedora:33:*:*:*:*:*:*:*
fedoraproject fedora 34 cpe:2.3:o:fedoraproject:fedora:34:*:*:*:*:*:*:*
debian debian_linux 10.0 cpe:2.3:o:debian:debian_linux:10.0:*:*:*:*:*:*:*

References for CVE-2021-33515

cvelogic Threat Intelligence