CVE-2020-13777 — GnuTLS 3.6.x before 3.6.14 uses incorrect cryptography for encrypting a session ticket (a loss of...
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.
Who exploits it and how urgent it is
A 0–100 score combining confirmed exploitation, ransomware and APT use, public exploits, EPSS and severity.
How the score was calculated
- EPSS 22.3% (30-day exploitation probability)+15
- Technical severity (high)+6
The score orders the patch queue; it does not replace your asset context (internet exposure, criticality, compensating controls).
Triage
Is it exploited, how likely is exploitation, what does it touch, and how severe do the sources call it.
Remediation
Fixes and mitigations documented by the sources — linked to the original advisory.
No fix documented by the sources we poll. That does not mean none exists: check the vendor advisory.
First 24 hours
Ordered from the record’s own fields — exposure first, because you cannot patch what you have not found. A rule-generated starting point.
- Identify exposed assets running the affected vendor/product/version combinations (Canonical Ubuntu Linux, Debian Debian Linux, Fedoraproject Fedora…).
- The attack is network-based and needs no privileges: restrict exposure (ACLs, VPN, WAF) until patched.
- No fix documented in the sources: reduce exposure and monitor the vendor advisory.
- EPSS ahead of 98% of scored CVEs: prioritize it in the patch queue.
- Search available logs for exploit probes matching the vulnerability class (cryptography), errors and authentication anomalies.
Affected scope
Vendor, product and versions as the sources word them.
| Vendor | Product | Versions | Status | Source |
|---|---|---|---|---|
| Canonical | Ubuntu Linux | version 19.10version 20.04 | Vulnerable | NIST National Vulnerability Database |
| Debian | Debian Linux | version 10.0 | Vulnerable | NIST National Vulnerability Database |
| Fedoraproject | Fedora | version 31version 32 | Vulnerable | NIST National Vulnerability Database |
| Gnu | Gnutls | ≥ 3.6.0 and < 3.6.14 | Vulnerable | NIST National Vulnerability Database |
Attack characteristics
The CVSS vector, decoded. It describes the attack, not your exposure to it.
Every base score collected
Sources score independently and may disagree; each row says who scored it and under which version.
| Score | Version | Severity | Expl. | Impact | Scored by |
|---|---|---|---|---|---|
| 7.4 | CVSS 3.1 | High | 2.2 | 5.2 | nvd@nist.gov via NIST National Vulnerability Database |
| 7.4 | CVSS 3.1 | High | — | — | GitHub, Inc. via GitHub Security Advisories |
| 5.8 | CVSS 2.0 | Medium | 8.6 | 4.9 | nvd@nist.gov via NIST National Vulnerability Database |
CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:N (score shown at the top: nvd@nist.gov) Weakness MITRE
Weakness class according to MITRE’s CWE catalog.
EPSS over time FIRST
Oct 13, 2026 → Oct 15, 2026 · 3 reading(s) · max 22.28%
Detection
Read off the CVSS vector and the weakness class. Starting points, not tested rules.
- Prioritize edge telemetry for the network-reachable component (proxy, WAF, IDS/IPS).
- Check TLS negotiations and unexpected certificates in the component’s traffic.
Timeline
What happened to this CVE, newest first.
- 2026
- Record published
- Affected products added · gnu/gnutls, fedoraproject/fedora, canonical/ubuntu linux, debian/debian linux
- CVSS changed · 7.4
- Source status changed · → Modified
- Record created in this database
- 2020
- CVE published
Source activity
Repeated readings are counted rather than listed.
- 2× References added · Oct 14, 2026 – Oct 14, 2026
- 1× Official description updated · Oct 14, 2026 – Oct 14, 2026
References
17 on the record
- gnutls.org/security-new.html
- usn.ubuntu.com/4384-1/
- lists.fedoraproject.org/archives/list/package-announce@lists.fedoraproject.org/message/VMB3UG
- lists.fedoraproject.org/archives/list/package-announce@lists.fedoraproject.org/message/6RTXZO
- lists.fedoraproject.org/archives/list/package-announce@lists.fedoraproject.org/message/RRQBFK
- www.debian.org/security/2020/dsa-4697
- lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/6C4D
- security.gentoo.org/glsa/202006-01
- lists.fedoraproject.org/archives/list/package-announce@lists.fedoraproject.org/message/6C4DHU
- lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/6RTX
- lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/VMB3
- security.netapp.com/advisory/ntap-20200619-0004/
- cert-portal.siemens.com/productcert/html/ssa-398330.html
- lists.opensuse.org/opensuse-security-announce/2020-06/msg00015.html
- github.com/advisories/GHSA-cv49-m792-xmjv
- nvd.nist.gov/vuln/detail/CVE-2020-13777
- lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/RRQB
Elsewhere on this site
Related CVEs (same products)
- High CVE-2026-12996 A use-after-free in OpenVPN 2.6.0 through 2.6.20 and 2.7_alpha1 through 2.7.4 allows remote... Jul 30, 2026
- Medium CVE-2026-14355 ext/openssl: Memory corruption in openssl_encrypt with AES-WRAP-PAD Jul 3, 2026
- Medium CVE-2026-56968 Use of Uninitialized Resource in Gnu Sasl Jun 23, 2026
- Medium CVE-2026-54231 Abrt: unsanitized systemd journal content written to dump directory files enables content injection Jun 13, 2026
- High CVE-2026-54230 Abrt: event handler scripts follow symlinks when writing output files, allowing arbitrary file overwrites Jun 13, 2026
- High CVE-2026-49975 Apache HTTP Server: mod_http2 denial of service Jun 8, 2026
Not in any source we poll
Listed rather than left blank: an empty field and an unmeasured one look identical on screen, and only one is a reason to look elsewhere.
- No fixed version, patch or mitigation documented.
- No CISA SSVC assessment.
- No confirmed IOCs, IP addresses, domains, file hashes, or malware artifacts supplied.
- No organization-specific asset inventory, compensating-control status, or patch deployment evidence supplied.
- No exploit packet captures, log samples, or incident case IDs supplied.
Answered from this record
Text assembled only from the fields above — no additional claims.
What should defenders know first?
CVE-2020-13777 is "GnuTLS 3.6.x before 3.6.14 uses incorrect cryptography for encrypting a session ticket (a loss of...", rated High. It affects Ubuntu Linux (Canonical); versions are in the scope table. It is not in CISA KEV, which does not rule out exploitation. CVSS 7.4 describes technical severity. EPSS 22.28% estimates the probability of exploitation in 30 days; neither replaces your asset context. First verify whether exposed or business-critical assets run the affected versions, apply vendor fixes or mitigations, and preserve logs for review.
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