CVE-2020-15917

common/session.c in Claws Mail before 3.17.6 has a protocol violation because suffix data after STARTTLS is mishandled.

Published: 2020-07-23 Last update: 2024-11-21 Assigner: [email protected] Source: [email protected]
NVD Status：Modified，CVE State: published
View at NVD, CVE.org, EUVD

CVE-2020-15917 is rated High Risk (67.8/100): CVSS Critical severity, with medium exploitation likelihood (EPSS 2.23%). 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-2020-15917

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 2025-11-21 3.00% 2.23% -0.77%
2 2025-11-18 2.23% 3.00% +0.77%
3 2025-03-30 — 2.23% —

Full EPSS history (16 records total)

Common vulnerability scoring system (CVSS) metrics for CVE-2020-15917

CVSS metrics for this CVE.

Base score Version Severity Vector Exploitability Impact Score source
9.8 3.1 CRITICAL
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/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: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:H)
Serious risk that confidential data gets exposed in a big way.
Integrity (I:H)
They could widely tamper with or forge data—trust in the data is badly hurt.
Availability (A:H)
Could take the service down hard or make it unusable for people who depend on it.
 3.9 5.9 [email protected]
7.5 2.0 HIGH
AV:N/AC:L/Au:N/C:P/I:P/A:P Click to expand
Access vector (AV:N)
Can be exploited remotely over network reachability.
Access complexity (AC:L)
Exploitation conditions are straightforward and predictable.
Authentication (AU:N)
No authentication is required.
Confidentiality impact (C:P)
Partial confidentiality impact.
Integrity impact (I:P)
Partial integrity impact.
Availability impact (A:P)
Partial availability impact.
 10.0 6.4 [email protected]

Weakness enumeration for CVE-2020-15917

OS Trackers for CVE-2020-15917

vendor priority summary link
alpine critical CVE-2020-15917: 1 source package rows (claws-mail); 7 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 0. https://security.alpinelinux.org/vuln/CVE-2020-15917
debian not yet assigned CVE-2020-15917 not yet assigned priority: Debian including 1 source packages (claws-mail), 5 status rows across 5 suites (bookworm, bullseye, forky, sid, trixie): resolved 5. https://security-tracker.debian.org/tracker/CVE-2020-15917
gentoo normal CVE-2020-15917: 1 GLSA(s) (202007-56), 1 atom(s) (mail-client/claws-mail); latest impact normal. https://bugs.gentoo.org/buglist.cgi?quicksearch=CVE-2020-15917
ubuntu low CVE-2020-15917 low priority: Ubuntu including 1 source packages (claws-mail), 16 status rows across 16 suites (bionic, focal, groovy, hirsute, impish, jammy, kinetic, lunar, mantic, noble, oracular, plucky, questing, trusty, upstream, xenial): not-affected 11, needs-triage 3, DNE 1, released 1. https://ubuntu.com/security/CVE-2020-15917

Affected software / configurations for CVE-2020-15917

Vendor Product Version Raw CPE
claws-mail claws-mail < 3.17.6 cpe:2.3:a:claws-mail:claws-mail:*:*:*:*:*:*:*:*
fedoraproject fedora 31 cpe:2.3:o:fedoraproject:fedora:31:*:*:*:*:*:*:*
fedoraproject fedora 32 cpe:2.3:o:fedoraproject:fedora:32:*:*:*:*:*:*:*
opensuse backports_sle 15.0 cpe:2.3:a:opensuse:backports_sle:15.0:sp1:*:*:*:*:*:*
opensuse backports_sle 15.0 cpe:2.3:a:opensuse:backports_sle:15.0:sp2:*:*:*:*:*:*
opensuse leap 15.1 cpe:2.3:o:opensuse:leap:15.1:*:*:*:*:*:*:*
opensuse leap 15.2 cpe:2.3:o:opensuse:leap:15.2:*:*:*:*:*:*:*

References for CVE-2020-15917

URL Tags
http://lists.opensuse.org/opensuse-security-announce/2020-07/msg00090.html Mailing List Third Party Advisory
http://lists.opensuse.org/opensuse-security-announce/2020-08/msg00002.html Broken Link Mailing List Third Party Advisory
http://lists.opensuse.org/opensuse-security-announce/2020-08/msg00060.html Broken Link Mailing List Third Party Advisory
http://lists.opensuse.org/opensuse-security-announce/2020-09/msg00051.html Broken Link Mailing List Third Party Advisory
http://lists.opensuse.org/opensuse-security-announce/2020-11/msg00013.html Broken Link Mailing List Third Party Advisory
https://git.claws-mail.org/?p=claws.git%3Ba=blob%3Bf=RELEASE_NOTES
https://git.claws-mail.org/?p=claws.git%3Ba=commit%3Bh=fcc25329049b6f9bd8d890f1197ed61eb12e14d5
https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/6YVQB7NRBHO67Q74RS7RZCMW4ENRVBB4/
https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/G7UX65342HRVDQML4G4GEVEUB764EUM5/
https://security.gentoo.org/glsa/202007-56 Third Party Advisory
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