CVE-2020-13777

GnuTLS 3.6.x before 3.6.14 uses incorrect cryptography for encrypting a session ticket (a loss of confidentiality in TLS 1.2, and an authentication bypass in TLS 1.3). The earliest affected version is 3.6.4 (2018-09-24) because of an error in a 2018-09-18 commit. Until the first key rotation, the TLS server always uses wrong data in place of an encryption key derived from an application.

Published: 2020-06-04 Last update: 2026-06-16 Assigner: [email protected] Source: [email protected]
NVD Status：Modified，CVE State: published
View at NVD, CVE.org, EUVD

CVE-2020-13777 is rated High Risk (68.5/100): CVSS High severity, with high exploitation likelihood (EPSS 17.51%, 97th percentile). EPSS ranks this CVE among the most likely to be exploited in the near term. EPSS rose +16.29% over the last day, indicating growing attacker interest. 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-2020-13777

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 2026-06-15 1.21% 17.51% +16.29%
2 2026-05-27 1.52% 1.21% -0.31%
3 2026-04-12 — 1.52% —

Full EPSS history (26 records total)

Common vulnerability scoring system (CVSS) metrics for CVE-2020-13777

CVSS metrics for this CVE.

Base score Version Severity Vector Exploitability Impact Score source
7.4 3.1 HIGH
CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/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: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:N)
Service keeps running; no real outage angle.
 2.2 5.2 [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-2020-13777

OS Trackers for CVE-2020-13777

vendor priority summary link
alpine high CVE-2020-13777: 1 source package rows (gnutls); 19 state rows across 9 repos (3.10-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 10. https://security.alpinelinux.org/vuln/CVE-2020-13777
debian not yet assigned CVE-2020-13777 not yet assigned priority: Debian including 1 source packages (gnutls28), 5 status rows across 5 suites (bookworm, bullseye, forky, sid, trixie): resolved 5. https://security-tracker.debian.org/tracker/CVE-2020-13777
gentoo normal CVE-2020-13777: 1 GLSA(s) (202006-01), 1 atom(s) (net-libs/gnutls); latest impact normal. https://bugs.gentoo.org/buglist.cgi?quicksearch=CVE-2020-13777
redhat high — https://access.redhat.com/security/cve/CVE-2020-13777
suse high CVE-2020-13777 severity important: SUSE including 381 source package names (0.1.0:libgnutls30-3.6.7-6.29.1, 0.1.75:libgnutls30-3.6.7-6.29.1, …), 477 product×package rows across 85 product lines (Container caasp/v4/389-ds, Container caasp/v4/busybox, … (85 product lines)): Fixed 259, Known Affected 157, Known Not Affected 61. https://www.suse.com/security/cve/CVE-2020-13777/
ubuntu high CVE-2020-13777 high priority: Ubuntu including 1 source packages (gnutls28), 6 status rows across 6 suites (bionic, eoan, focal, trusty, upstream, xenial): released 3, not-affected 2, DNE 1. https://ubuntu.com/security/CVE-2020-13777

Affected software / configurations for CVE-2020-13777

Vendor Product Version Raw CPE
gnu gnutls >= 3.6.0, < 3.6.14 cpe:2.3:a:gnu:gnutls:*:*:*:*:*:*:*:*
fedoraproject fedora 31 cpe:2.3:o:fedoraproject:fedora:31:*:*:*:*:*:*:*
fedoraproject fedora 32 cpe:2.3:o:fedoraproject:fedora:32:*:*:*:*:*:*:*
canonical ubuntu_linux 19.10 cpe:2.3:o:canonical:ubuntu_linux:19.10:*:*:*:*:*:*:*
canonical ubuntu_linux 20.04 cpe:2.3:o:canonical:ubuntu_linux:20.04:*:*:*:lts:*:*:*
debian debian_linux 10.0 cpe:2.3:o:debian:debian_linux:10.0:*:*:*:*:*:*:*

References for CVE-2020-13777

URL Tags
http://lists.opensuse.org/opensuse-security-announce/2020-06/msg00015.html Broken Link
https://gnutls.org/security-new.html#GNUTLS-SA-2020-06-03 Vendor Advisory
https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/6C4DHUKV6M6SJ5CV6KVHZNHNF7HCUE5P/
https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/6RTXZOXC4MHTFE2HKY6IAZMF2WHD2WMV/
https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/RRQBFK3UZ7SV76IYDTS4PS6ABS2DSJHK/
https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/VMB3UGI5H5RCFRU6OGRPMNUCNLJGEN7Y/
https://security.gentoo.org/glsa/202006-01 Third Party Advisory
https://security.netapp.com/advisory/ntap-20200619-0004/ Third Party Advisory
https://usn.ubuntu.com/4384-1/ Third Party Advisory
https://www.debian.org/security/2020/dsa-4697 Third Party Advisory
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