# CVE-2020-17049: Kerberos KDC Security Feature Bypass Vulnerability > Attackers can bypass Kerberos Constrained Delegation restrictions by tampering with service tickets, requiring a compromised service configured for KCD. - **Severity:** Medium 6.6 (`CVSS:3.1/AV:N/AC:H/PR:H/UI:N/S:U/C:H/I:H/A:H/E:U/RL:O/RC:C`) - **Exploited in the wild:** Not known - **Login needed:** An administrator - **Attackable:** Over the internet - **Victim action needed:** Not needed - **Fix available:** Yes - **Published:** 11 Nov 2020 - **Updated:** 15 Nov 2024 - **Also known as:** ALSA-2023:2570, AZL-10661, AZL-36992, GHSA-g2p3-j47p-8cwj, RHSA-2023:2570, openSUSE-SU-2024:13200-1 ## What is CVE-2020-17049? CVE-2020-17049 is a medium-severity vulnerability in Microsoft Windows Server 2012, published on 11 Nov 2020. An attacker needs administrator access to exploit it, with no action from the victim. ### Official description A security feature bypass vulnerability exists in the way Key Distribution Center (KDC) determines if a service ticket can be used for delegation via Kerberos Constrained Delegation (KCD). To exploit the vulnerability, a compromised service that is configured to use KCD could tamper with a service ticket that is not valid for delegation to force the KDC to accept it. The update addresses this vulnerability by changing how the KDC validates service tickets used with KCD. Weakness: CWE-863 (Incorrect Authorization) ## Which versions are affected by CVE-2020-17049? It affects 4 products. | Package | Ecosystem | Affected | Fixed in | | --- | --- | --- | --- | | `krb5-devel` | AlmaLinux:9 | All versions | 1.20.1-8.el9 | | `krb5-libs` | AlmaLinux:9 | All versions | 1.20.1-8.el9 | | `krb5-pkinit` | AlmaLinux:9 | All versions | 1.20.1-8.el9 | | `krb5-server` | AlmaLinux:9 | All versions | 1.20.1-8.el9 | | `krb5-server-ldap` | AlmaLinux:9 | All versions | 1.20.1-8.el9 | | `krb5-workstation` | AlmaLinux:9 | All versions | 1.20.1-8.el9 | | `libkadm5` | AlmaLinux:9 | All versions | 1.20.1-8.el9 | | `krb5-devel` | Red Hat:enterprise_linux:9::appstream | All versions | 0:1.20.1-8.el9 | | `krb5` | Red Hat:enterprise_linux:9::baseos | All versions | 0:1.20.1-8.el9 | | `krb5-debuginfo` | Red Hat:enterprise_linux:9::baseos | All versions | 0:1.20.1-8.el9 | | `krb5-debugsource` | Red Hat:enterprise_linux:9::baseos | All versions | 0:1.20.1-8.el9 | | `krb5-libs` | Red Hat:enterprise_linux:9::baseos | All versions | 0:1.20.1-8.el9 | | `krb5-libs-debuginfo` | Red Hat:enterprise_linux:9::baseos | All versions | 0:1.20.1-8.el9 | | `krb5-pkinit` | Red Hat:enterprise_linux:9::baseos | All versions | 0:1.20.1-8.el9 | | `krb5-pkinit-debuginfo` | Red Hat:enterprise_linux:9::baseos | All versions | 0:1.20.1-8.el9 | | `krb5-server` | Red Hat:enterprise_linux:9::baseos | All versions | 0:1.20.1-8.el9 | | `krb5-server-debuginfo` | Red Hat:enterprise_linux:9::baseos | All versions | 0:1.20.1-8.el9 | | `krb5-server-ldap` | Red Hat:enterprise_linux:9::baseos | All versions | 0:1.20.1-8.el9 | | `krb5-server-ldap-debuginfo` | Red Hat:enterprise_linux:9::baseos | All versions | 0:1.20.1-8.el9 | | `krb5-workstation` | Red Hat:enterprise_linux:9::baseos | All versions | 0:1.20.1-8.el9 | | `krb5-workstation-debuginfo` | Red Hat:enterprise_linux:9::baseos | All versions | 0:1.20.1-8.el9 | | `libkadm5` | Red Hat:enterprise_linux:9::baseos | All versions | 0:1.20.1-8.el9 | | `libkadm5-debuginfo` | Red Hat:enterprise_linux:9::baseos | All versions | 0:1.20.1-8.el9 | Products: Microsoft Windows Server 2012, Microsoft Windows Server 2016, Microsoft Windows Server 2019, Samba Samba. ## How do I fix CVE-2020-17049? Apply the vendor's patch. ## Is CVE-2020-17049 being exploited? There is no known exploitation of CVE-2020-17049 in the wild and no public exploit code. ## Other vulnerabilities in Microsoft Windows Server 2012 - [CVE-2025-59287](https://insights.sbomify.com/CVE-2025-59287/): Microsoft Windows Server Update Service (WSUS) Deserialization of Untrusted Data (critical 9.8, exploited in the wild) - [CVE-2026-69595](https://insights.sbomify.com/CVE-2026-69595/): Windows Services for NFS ONCRPC XDR Driver Remote Code Execution Vulnerability (critical 9.8) - [CVE-2026-78445](https://insights.sbomify.com/CVE-2026-78445/): Windows Services for NFS ONCRPC XDR Driver Remote Code Execution Vulnerability (critical 9.8) - [CVE-2026-41089](https://insights.sbomify.com/CVE-2026-41089/): Windows Netlogon Remote Code Execution Vulnerability (critical 9.8) - [CVE-2024-43639](https://insights.sbomify.com/CVE-2024-43639/): Windows KDC Proxy Remote Code Execution Vulnerability (critical 9.8) ## Fix prompt for AI coding agents ```text Check this codebase for CVE-2020-17049 and fix it if it is affected. What it is: CVE-2020-17049 is a medium-severity vulnerability in Microsoft Windows Server 2012, published on 11 Nov 2020. An attacker needs administrator access to exploit it, with no action from the victim. Exploitation: There is no known exploitation of CVE-2020-17049 in the wild and no public exploit code. Affected product: Microsoft Windows Server 2012. 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-2020-17049/ (Markdown: https://insights.sbomify.com/CVE-2020-17049/index.md) ``` ## Sources - CVE record: https://www.cve.org/CVERecord?id=CVE-2020-17049 - NVD: https://nvd.nist.gov/vuln/detail/CVE-2020-17049 - OSV: https://osv.dev/vulnerability/CVE-2020-17049 --- From sbomify Insights: https://insights.sbomify.com/CVE-2020-17049/ Summaries are generated and may contain mistakes; the official description above is the record.