FedoraOperating system · Fedoraproject
CVE-2020-13777
Official description Straight from the sourceThe vendor's or NVD's own wording, published unedited. Authoritative, but often terse — it says what broke, rarely what to do.
NVD · uneditedGnuTLS 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.
Technical summary Written by usOur analysis, written from the advisory, the CVSS vector and the affected-version data. It adds context the advisory leaves out, and never invents facts that are not in the source.
dbcve analysis · high confidenceGnuTLS versions 3.6.x before 3.6.14 contain a critical cryptographic flaw where session tickets are encrypted with incorrect key material instead of an application-derived encryption key. This vulnerability, introduced in a September 2018 commit, causes loss of confidentiality in TLS 1.2 connections and enables authentication bypass in TLS 1.3 until the first key rotation occurs.
Verify against the referenced sources before acting — the references below are authoritative for this CVE, this summary is not.
Affected products & versions What the vendor confirmedThe version ranges the vendor confirmed as vulnerable. If your version sits inside a range here, treat yourself as exposed until you have upgraded.
NVD · CPE data
FedoraOperating system
= 31= 32
Ubuntu LinuxOperating system
= 19.10= 20.04
Debian LinuxOperating system
= 10.0>= 3.6.0, < 3.6.14CVSS breakdown How the score is builtThe industry scoring standard. It rates how the flaw is reached, what it takes to exploit, and what an attacker gains — the score is derived from those, not the other way round.
From the vector- Attack vector
- Network
- Complexity
- High
- Privileges
- None
- User interaction
- None
- Scope
- Unchanged
- Confidentiality
- High
- Integrity
- High
- Availability
- None
CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:N
Am I affected? How to checkSteps we derive from the advisory and the affected-version data, so you can decide whether this CVE reaches your setup. They are a guide, not a scan — your own configuration is the authority.
dbcve checksWork through these to decide whether this CVE applies to you.
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Identify installed GnuTLS versionRun 'gnutls-cli --version' or check the package manager (rpm -q gnutls, dpkg -l libgnutls30)Affected if The version is 3.6.x where x is 0 through 13 (any version >= 3.6.0 but < 3.6.14)
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Confirm the library version in useIf GnuTLS is used by a specific application, inspect the linked library version with 'ldd <executable> | grep gnutls' or check /usr/lib/x86_64-linux-gnu/libgnutls*.so*Affected if The linked library version falls within the vulnerable 3.6.0 to 3.6.13 range
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Determine if TLS session tickets are enabledInspect the application or server configuration for TLS session ticket settings (look for session tickets, session resumption, or TLS ticket keywords in config files or running processes)Affected if Session tickets are enabled - this is the vulnerable feature that uses the incorrect key material
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Verify TLS usage in the environmentReview active TLS connections or server configs to confirm TLS 1.2 or TLS 1.3 is in useAffected if TLS 1.2 or TLS 1.3 connections are active - TLS 1.2 loses confidentiality, TLS 1.3 allows authentication bypass until first key rotation
You are affected if GnuTLS version 3.6.0 through 3.6.13 is installed AND TLS session tickets are enabled in your TLS configuration.
Generated from the published advisory. Verify against your own configuration.
Remediation Closing itWhat it takes to close this. Where a vendor fix exists we point at it; where none exists we say so plainly, and can build one. Effort estimates are scoped from the advisory, not from your codebase.
From vendor data3.6.14
Upgrade GnuTLS to version 3.6.14 or later to obtain the correct cryptographic implementation for session ticket encryption. Prioritize systems using TLS 1.3 given the authentication bypass impact.
Fix this in Fedora
Scoped from the published advisory
- Consultation6.0 h
- Implementation8.0 h
- Testing8.0 h
- Review / QA4.0 h
An estimate, not a bill — we confirm scope with you before any work starts. Need it this week? Rush from $7,296.
Scan for this in your stack
Free · runs locallyCheck whether your project pulls in CVE-2020-13777 — or any other known-vulnerable package — straight from your lock files. Free and open source; it runs locally and uploads nothing.
References Go to the primary sourcePrimary sources — vendor advisories, patches and trackers. Where our summary and a reference disagree, the reference wins.
Primary sourcesPractitioner notes
ContributedPeer-ranked notes from engineers who’ve handled CVE-2020-13777 in production — separate from our analysis above.
The advisory tells you what broke. It rarely tells you what actually worked. If you’ve dealt with this one, that detail is what the next engineer is searching for.
- The version that genuinely resolved it — not the one the vendor claimed
- A config change or rule that shut the vector down
- A gotcha in the upgrade path that cost you an afternoon
No notes yet
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- Version or environment caveats, and links to real fixes
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