# CVE-2020-26117: Security feature bypass in n/a > TigerVNC viewers mishandle TLS certificate exceptions, allowing certificate owners to impersonate servers after a user adds an exception. - **Severity:** High 8.1 (`CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:N`) - **Exploited in the wild:** Not known - **Login needed:** Not needed - **Attackable:** Over the internet - **Victim action needed:** A user has to click or open something - **Fix available:** Yes - **Published:** 27 Sep 2020 - **Updated:** 4 Aug 2024 - **Also known as:** DEBIAN-CVE-2020-26117, DLA-2396-1, GHSA-cx25-8g49-fx7q, MGASA-2020-0388, RHSA-2021:1783, RLSA-2021:1783, SUSE-SU-2020:2880-1, SUSE-SU-2020:2881-1, SUSE-SU-2020:2882-1, SUSE-SU-2020:2898-1, UBUNTU-CVE-2020-26117, USN-5965-1, openSUSE-SU-2020:1666-1, openSUSE-SU-2020:1841-1 ## What is CVE-2020-26117? CVE-2020-26117 is a high-severity vulnerability in Debian Debian Linux, published on 27 Sep 2020. An attacker can exploit it over the internet without logging in, and only if a user opens a file or follows a link. ### Official description In rfb/CSecurityTLS.cxx and rfb/CSecurityTLS.java in TigerVNC before 1.11.0, viewers mishandle TLS certificate exceptions. They store the certificates as authorities, meaning that the owner of a certificate could impersonate any server after a client had added an exception. Weakness: CWE-295 (Improper Certificate Validation) ## Which versions are affected by CVE-2020-26117? It affects 3 products. | Package | Ecosystem | Affected | Fixed in | | --- | --- | --- | --- | | `tigervnc` | Red Hat:enterprise_linux:8::appstream | All versions | 0:1.11.0-6.el8 | | `tigervnc-debuginfo` | Red Hat:enterprise_linux:8::appstream | All versions | 0:1.11.0-6.el8 | | `tigervnc-debugsource` | Red Hat:enterprise_linux:8::appstream | All versions | 0:1.11.0-6.el8 | | `tigervnc-icons` | Red Hat:enterprise_linux:8::appstream | All versions | 0:1.11.0-6.el8 | | `tigervnc-license` | Red Hat:enterprise_linux:8::appstream | All versions | 0:1.11.0-6.el8 | | `tigervnc-selinux` | Red Hat:enterprise_linux:8::appstream | All versions | 0:1.11.0-6.el8 | | `tigervnc-server` | Red Hat:enterprise_linux:8::appstream | All versions | 0:1.11.0-6.el8 | | `tigervnc-server-debuginfo` | Red Hat:enterprise_linux:8::appstream | All versions | 0:1.11.0-6.el8 | | `tigervnc-server-minimal` | Red Hat:enterprise_linux:8::appstream | All versions | 0:1.11.0-6.el8 | | `tigervnc-server-minimal-debuginfo` | Red Hat:enterprise_linux:8::appstream | All versions | 0:1.11.0-6.el8 | | `tigervnc-server-module` | Red Hat:enterprise_linux:8::appstream | All versions | 0:1.11.0-6.el8 | | `tigervnc-server-module-debuginfo` | Red Hat:enterprise_linux:8::appstream | All versions | 0:1.11.0-6.el8 | | `tigervnc` | Rocky Linux:8 | All versions | 0:1.11.0-6.el8 | | `tigervnc` | SUSE:Enterprise Storage 5 | All versions | 1.6.0-27.1 | | `tigervnc` | SUSE:HPE Helion OpenStack 8 | All versions | 1.6.0-27.1 | | `tigervnc` | SUSE:Linux Enterprise High Performance Computing 15-ESPOS | All versions | 1.8.0-13.14.1 | | `tigervnc` | SUSE:Linux Enterprise High Performance Computing 15-LTSS | All versions | 1.8.0-13.14.1 | | `tigervnc` | SUSE:Linux Enterprise Module for Basesystem 15 SP1 | All versions | 1.9.0-19.9.1 | | `tigervnc` | SUSE:Linux Enterprise Module for Basesystem 15 SP2 | All versions | 1.9.0-19.9.1 | | `tigervnc` | SUSE:Linux Enterprise Module for Desktop Applications 15 SP1 | All versions | 1.9.0-19.9.1 | | `tigervnc` | SUSE:Linux Enterprise Module for Desktop Applications 15 SP2 | All versions | 1.9.0-19.9.1 | | `tigervnc` | SUSE:Linux Enterprise Server 12 SP2-BCL | All versions | 1.6.0-27.1 | | `tigervnc` | SUSE:Linux Enterprise Server 12 SP2-LTSS | All versions | 1.6.0-27.1 | | `tigervnc` | SUSE:Linux Enterprise Server 12 SP3-BCL | All versions | 1.6.0-27.1 | | `tigervnc` | SUSE:Linux Enterprise Server 12 SP3-LTSS | All versions | 1.6.0-27.1 | | `tigervnc` | SUSE:Linux Enterprise Server 12 SP4-LTSS | All versions | 1.6.0-22.17.1 | | `tigervnc` | SUSE:Linux Enterprise Server 12 SP5 | All versions | 1.6.0-22.17.1 | | `tigervnc` | SUSE:Linux Enterprise Server 15-LTSS | All versions | 1.8.0-13.14.1 | | `tigervnc` | SUSE:Linux Enterprise Server for SAP Applications 12 SP2 | All versions | 1.6.0-27.1 | | `tigervnc` | SUSE:Linux Enterprise Server for SAP Applications 12 SP3 | All versions | 1.6.0-27.1 | | `tigervnc` | SUSE:Linux Enterprise Server for SAP Applications 12 SP4 | All versions | 1.6.0-22.17.1 | | `tigervnc` | SUSE:Linux Enterprise Server for SAP Applications 12 SP5 | All versions | 1.6.0-22.17.1 | | `tigervnc` | SUSE:Linux Enterprise Server for SAP Applications 15 | All versions | 1.8.0-13.14.1 | | `tigervnc` | SUSE:OpenStack Cloud 7 | All versions | 1.6.0-27.1 | | `tigervnc` | SUSE:OpenStack Cloud 8 | All versions | 1.6.0-27.1 | | `tigervnc` | SUSE:OpenStack Cloud 9 | All versions | 1.6.0-22.17.1 | | `tigervnc` | SUSE:OpenStack Cloud Crowbar 8 | All versions | 1.6.0-27.1 | | `tigervnc` | SUSE:OpenStack Cloud Crowbar 9 | All versions | 1.6.0-22.17.1 | | `tigervnc` | openSUSE:Leap 15.1 | All versions | 1.9.0-lp151.4.9.1 | | `tigervnc` | openSUSE:Leap 15.2 | All versions | 1.9.0-lp152.7.3.1 | Products: Debian Debian Linux, Opensuse Leap, Tigervnc Tigervnc. ## How do I fix CVE-2020-26117? Upgrade to a fixed version. ## Is CVE-2020-26117 being exploited? There is no known exploitation of CVE-2020-26117 in the wild and no public exploit code. ## Other vulnerabilities in Debian Debian Linux - [CVE-2015-3306](https://insights.sbomify.com/CVE-2015-3306/): ProFTPD Improper Access Control (critical 10.0, exploited in the wild) - [CVE-2025-49113](https://insights.sbomify.com/CVE-2025-49113/): RoundCube Webmail Deserialization of Untrusted Data (critical 9.9, exploited in the wild) - [CVE-2026-24061](https://insights.sbomify.com/CVE-2026-24061/): GNU InetUtils Argument Injection (critical 9.8, exploited in the wild) - [CVE-2025-39682](https://insights.sbomify.com/CVE-2025-39682/): Linux Kernel Improper Check for Unusual or Exceptional Conditions (critical 9.8, exploited in the wild) - [CVE-2024-9680](https://insights.sbomify.com/CVE-2024-9680/): Mozilla Firefox Use-After-Free (critical 9.8, exploited in the wild) ## Fix prompt for AI coding agents ```text Check this codebase for CVE-2020-26117 and fix it if it is affected. What it is: CVE-2020-26117 is a high-severity vulnerability in Debian Debian Linux, published on 27 Sep 2020. An attacker can exploit it over the internet without logging in, and only if a user opens a file or follows a link. Exploitation: There is no known exploitation of CVE-2020-26117 in the wild and no public exploit code. Affected product: Debian Debian 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-2020-26117/ (Markdown: https://insights.sbomify.com/CVE-2020-26117/index.md) ``` ## Sources - CVE record: https://www.cve.org/CVERecord?id=CVE-2020-26117 - NVD: https://nvd.nist.gov/vuln/detail/CVE-2020-26117 - OSV: https://osv.dev/vulnerability/CVE-2020-26117 --- From sbomify Insights: https://insights.sbomify.com/CVE-2020-26117/ Summaries are generated and may contain mistakes; the official description above is the record.