# 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 authent - **Severity:** High 7.4 (`CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:N`) - **Exploited in the wild:** Not known - **Fix available:** Yes - **Published:** 4 Jun 2020 - **Updated:** 14 Oct 2026 - **Also known as:** ALPINE-CVE-2020-13777, DEBIAN-CVE-2020-13777, DSA-4697-1, GHSA-cv49-m792-xmjv, JLSEC-2026-518, MGASA-2020-0268, RHSA-2020:2637, RHSA-2020:2638, RHSA-2020:2639, SUSE-SU-2020:1584-1, UBUNTU-CVE-2020-13777, USN-4384-1, openSUSE-SU-2020:0790-1 ## What is CVE-2020-13777? CVE-2020-13777 is a high-severity vulnerability in Canonical Ubuntu Linux, published on 4 Jun 2020. ### Official description 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. Weakness: CWE-327 (Use of a Broken or Risky Cryptographic Algorithm) ## Which versions are affected by CVE-2020-13777? It affects 4 products. | Package | Ecosystem | Affected | Fixed in | | --- | --- | --- | --- | | `gnutls-c++` | Red Hat:enterprise_linux:8::appstream | All versions | 0:3.6.8-11.el8_2 | | `gnutls-c++-debuginfo` | Red Hat:enterprise_linux:8::appstream | All versions | 0:3.6.8-11.el8_2 | | `gnutls-dane` | Red Hat:enterprise_linux:8::appstream | All versions | 0:3.6.8-11.el8_2 | | `gnutls-dane-debuginfo` | Red Hat:enterprise_linux:8::appstream | All versions | 0:3.6.8-11.el8_2 | | `gnutls-debuginfo` | Red Hat:enterprise_linux:8::appstream | All versions | 0:3.6.8-11.el8_2 | | `gnutls-debugsource` | Red Hat:enterprise_linux:8::appstream | All versions | 0:3.6.8-11.el8_2 | | `gnutls-devel` | Red Hat:enterprise_linux:8::appstream | All versions | 0:3.6.8-11.el8_2 | | `gnutls-utils` | Red Hat:enterprise_linux:8::appstream | All versions | 0:3.6.8-11.el8_2 | | `gnutls-utils-debuginfo` | Red Hat:enterprise_linux:8::appstream | All versions | 0:3.6.8-11.el8_2 | | `gnutls` | Red Hat:enterprise_linux:8::baseos | All versions | 0:3.6.8-11.el8_2 | | `gnutls-c++-debuginfo` | Red Hat:enterprise_linux:8::baseos | All versions | 0:3.6.8-11.el8_2 | | `gnutls-dane-debuginfo` | Red Hat:enterprise_linux:8::baseos | All versions | 0:3.6.8-11.el8_2 | | `gnutls-debuginfo` | Red Hat:enterprise_linux:8::baseos | All versions | 0:3.6.8-11.el8_2 | | `gnutls-debugsource` | Red Hat:enterprise_linux:8::baseos | All versions | 0:3.6.8-11.el8_2 | | `gnutls-utils-debuginfo` | Red Hat:enterprise_linux:8::baseos | All versions | 0:3.6.8-11.el8_2 | | `gnutls-c++` | Red Hat:rhel_e4s:8.0::appstream | All versions | 0:3.6.5-3.el8_0 | | `gnutls-c++-debuginfo` | Red Hat:rhel_e4s:8.0::appstream | All versions | 0:3.6.5-3.el8_0 | | `gnutls-dane` | Red Hat:rhel_e4s:8.0::appstream | All versions | 0:3.6.5-3.el8_0 | | `gnutls-dane-debuginfo` | Red Hat:rhel_e4s:8.0::appstream | All versions | 0:3.6.5-3.el8_0 | | `gnutls-debuginfo` | Red Hat:rhel_e4s:8.0::appstream | All versions | 0:3.6.5-3.el8_0 | | `gnutls-debugsource` | Red Hat:rhel_e4s:8.0::appstream | All versions | 0:3.6.5-3.el8_0 | | `gnutls-devel` | Red Hat:rhel_e4s:8.0::appstream | All versions | 0:3.6.5-3.el8_0 | | `gnutls-utils` | Red Hat:rhel_e4s:8.0::appstream | All versions | 0:3.6.5-3.el8_0 | | `gnutls-utils-debuginfo` | Red Hat:rhel_e4s:8.0::appstream | All versions | 0:3.6.5-3.el8_0 | | `gnutls` | Red Hat:rhel_e4s:8.0::baseos | All versions | 0:3.6.5-3.el8_0 | | `gnutls-c++-debuginfo` | Red Hat:rhel_e4s:8.0::baseos | All versions | 0:3.6.5-3.el8_0 | | `gnutls-dane-debuginfo` | Red Hat:rhel_e4s:8.0::baseos | All versions | 0:3.6.5-3.el8_0 | | `gnutls-debuginfo` | Red Hat:rhel_e4s:8.0::baseos | All versions | 0:3.6.5-3.el8_0 | | `gnutls-debugsource` | Red Hat:rhel_e4s:8.0::baseos | All versions | 0:3.6.5-3.el8_0 | | `gnutls-utils-debuginfo` | Red Hat:rhel_e4s:8.0::baseos | All versions | 0:3.6.5-3.el8_0 | | `gnutls-c++` | Red Hat:rhel_eus:8.1::appstream | All versions | 0:3.6.8-9.el8_1 | | `gnutls-c++-debuginfo` | Red Hat:rhel_eus:8.1::appstream | All versions | 0:3.6.8-9.el8_1 | | `gnutls-dane` | Red Hat:rhel_eus:8.1::appstream | All versions | 0:3.6.8-9.el8_1 | | `gnutls-dane-debuginfo` | Red Hat:rhel_eus:8.1::appstream | All versions | 0:3.6.8-9.el8_1 | | `gnutls-debuginfo` | Red Hat:rhel_eus:8.1::appstream | All versions | 0:3.6.8-9.el8_1 | | `gnutls-debugsource` | Red Hat:rhel_eus:8.1::appstream | All versions | 0:3.6.8-9.el8_1 | | `gnutls-devel` | Red Hat:rhel_eus:8.1::appstream | All versions | 0:3.6.8-9.el8_1 | | `gnutls-utils` | Red Hat:rhel_eus:8.1::appstream | All versions | 0:3.6.8-9.el8_1 | | `gnutls-utils-debuginfo` | Red Hat:rhel_eus:8.1::appstream | All versions | 0:3.6.8-9.el8_1 | | `gnutls` | Red Hat:rhel_eus:8.1::baseos | All versions | 0:3.6.8-9.el8_1 | Products: Canonical Ubuntu Linux, Debian Debian Linux, Fedoraproject Fedora, Gnu Gnutls. ## How do I fix CVE-2020-13777? Upgrade to a fixed version. ## Is CVE-2020-13777 being exploited? There is no known exploitation of CVE-2020-13777 in the wild and no public exploit code. Public exploit code: - Zeek script to detect servers vulnerable to CVE-2020-13777 (github_poc): https://github.com/0xxon/cve-2020-13777 - Challange CVE-2020-13777 (github_poc): https://github.com/shigeki/challenge_CVE-2020-13777 - https://github.com/prprhyt/PoC_TLS1_3_CVE-2020-13777 (github_poc): https://github.com/prprhyt/PoC_TLS1_3_CVE-2020-13777 ## Other vulnerabilities in Canonical Ubuntu Linux - [CVE-2020-11651](https://insights.sbomify.com/CVE-2020-11651/): SaltStack Salt Authentication Bypass (critical 9.8, exploited in the wild) - [CVE-2020-7247](https://insights.sbomify.com/CVE-2020-7247/): OpenSMTPD Remote Code Execution (critical 9.8, exploited in the wild) - [CVE-2019-16928](https://insights.sbomify.com/CVE-2019-16928/): Exim Out-of-bounds Write (critical 9.8, exploited in the wild) - [CVE-2018-6789](https://insights.sbomify.com/CVE-2018-6789/): Exim Buffer Overflow (critical 9.8, exploited in the wild) - [CVE-2015-2590](https://insights.sbomify.com/CVE-2015-2590/): Oracle Java SE and Java SE Embedded Remote Code Execution (critical 9.8, exploited in the wild) ## Fix prompt for AI coding agents ```text Check this codebase for CVE-2020-13777 and fix it if it is affected. What it is: CVE-2020-13777 is a high-severity vulnerability in Canonical Ubuntu Linux, published on 4 Jun 2020. Exploitation: There is no known exploitation of CVE-2020-13777 in the wild and no public exploit code. Affected product: Canonical Ubuntu Linux. No package-level version data is available, so check the vendor advisory linked from the reference page. Task: 1. Search the dependency manifests and lockfiles (for example package.json, package-lock.json, requirements.txt, poetry.lock, uv.lock, pom.xml, build.gradle, go.mod, Cargo.lock, Gemfile.lock) and any Dockerfiles for the affected packages, including transitive dependencies. 2. If an affected version is in use, upgrade it to the fixed version for its release line with the project's package manager, so the lockfile is regenerated. Prefer the smallest upgrade that fixes it. 3. If there is no fix, or the upgrade would break the build, do not guess: explain the risk and the safest workaround instead. 4. Run the tests and summarise what changed and why. 5. If nothing in the project is affected, say so and change nothing. Reference: https://insights.sbomify.com/CVE-2020-13777/ (Markdown: https://insights.sbomify.com/CVE-2020-13777/index.md) ``` ## Sources - CVE record: https://www.cve.org/CVERecord?id=CVE-2020-13777 - NVD: https://nvd.nist.gov/vuln/detail/CVE-2020-13777 - OSV: https://osv.dev/vulnerability/CVE-2020-13777 --- From sbomify Insights: https://insights.sbomify.com/CVE-2020-13777/ Summaries are generated and may contain mistakes; the official description above is the record.