# CVE-2025-21521: Denial of service in MySQL Server > Unauthenticated attackers can cause a complete denial of service in MySQL Server via network access, requiring immediate patching. - **Severity:** High 7.5 (`CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H`) - **Exploited in the wild:** Not known - **Login needed:** Not needed - **Attackable:** Over the internet - **Victim action needed:** Not needed - **Fix available:** Yes - **Published:** 21 Jan 2025 - **Updated:** 3 Nov 2025 - **Also known as:** AZL-63039, GHSA-2rgw-wmwq-m2w3, RHBA-2025:5321, RHSA-2025:1755, RHSA-2025:1756, RHSA-2025:1757, RHSA-2025:1766, RHSA-2025:1767, RHSA-2025:2882, RHSA-2025:2883, UBUNTU-CVE-2025-21521 ## What is CVE-2025-21521? CVE-2025-21521 is a high-severity denial of service vulnerability in Oracle Mysql Server, published on 21 Jan 2025. An attacker can exploit it over the internet without logging in, with no action from the victim. ### Official description Vulnerability in the MySQL Server product of Oracle MySQL (component: Server: Thread Pooling). Supported versions that are affected are 8.0.39 and prior, 8.4.2 and prior and 9.0.1 and prior. Easily exploitable vulnerability allows unauthenticated attacker with network access via multiple protocols to compromise MySQL Server. Successful attacks of this vulnerability can result in unauthorized ability to cause a hang or frequently repeatable crash (complete DOS) of MySQL Server. CVSS 3.1 Base Score 7.5 (Availability impacts). CVSS Vector: (CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H). Weakness: CWE-770 (Allocation of Resources Without Limits or Throttling) ## Which versions are affected by CVE-2025-21521? It affects 1 product. | Package | Ecosystem | Affected | Fixed in | | --- | --- | --- | --- | | `mysql8.4` | Red Hat:enterprise_linux:10.0 | All versions | 0:8.4.4-2.el10 | | `mysql8.4-common` | Red Hat:enterprise_linux:10.0 | All versions | 0:8.4.4-2.el10 | | `mysql8.4-debuginfo` | Red Hat:enterprise_linux:10.0 | All versions | 0:8.4.4-2.el10 | | `mysql8.4-debugsource` | Red Hat:enterprise_linux:10.0 | All versions | 0:8.4.4-2.el10 | | `mysql8.4-devel` | Red Hat:enterprise_linux:10.0 | All versions | 0:8.4.4-2.el10 | | `mysql8.4-devel-debuginfo` | Red Hat:enterprise_linux:10.0 | All versions | 0:8.4.4-2.el10 | | `mysql8.4-errmsg` | Red Hat:enterprise_linux:10.0 | All versions | 0:8.4.4-2.el10 | | `mysql8.4-libs` | Red Hat:enterprise_linux:10.0 | All versions | 0:8.4.4-2.el10 | | `mysql8.4-libs-debuginfo` | Red Hat:enterprise_linux:10.0 | All versions | 0:8.4.4-2.el10 | | `mysql8.4-server` | Red Hat:enterprise_linux:10.0 | All versions | 0:8.4.4-2.el10 | | `mysql8.4-server-debuginfo` | Red Hat:enterprise_linux:10.0 | All versions | 0:8.4.4-2.el10 | | `mysql8.4-test` | Red Hat:enterprise_linux:10.0 | All versions | 0:8.4.4-2.el10 | | `mysql8.4-test-data` | Red Hat:enterprise_linux:10.0 | All versions | 0:8.4.4-2.el10 | | `mysql8.4-test-debuginfo` | Red Hat:enterprise_linux:10.0 | All versions | 0:8.4.4-2.el10 | | `mecab` | Red Hat:rhel_aus:8.2::appstream | All versions | 0:0.996-1.module+el8.0.0+3898+e09bb8de.9 | | `mecab-debuginfo` | Red Hat:rhel_aus:8.2::appstream | All versions | 0:0.996-1.module+el8.0.0+3898+e09bb8de.9 | | `mecab-debugsource` | Red Hat:rhel_aus:8.2::appstream | All versions | 0:0.996-1.module+el8.0.0+3898+e09bb8de.9 | | `mecab-ipadic` | Red Hat:rhel_aus:8.2::appstream | All versions | 0:2.7.0.20070801-16.module+el8.0.0+3898+e09bb8de | | `mecab-ipadic-EUCJP` | Red Hat:rhel_aus:8.2::appstream | All versions | 0:2.7.0.20070801-16.module+el8.0.0+3898+e09bb8de | | `mysql` | Red Hat:rhel_aus:8.2::appstream | All versions | 0:8.0.40-1.module+el8.2.0+22898+0bdd8c5b.4 | | `mysql-common` | Red Hat:rhel_aus:8.2::appstream | All versions | 0:8.0.40-1.module+el8.2.0+22898+0bdd8c5b.4 | | `mysql-debuginfo` | Red Hat:rhel_aus:8.2::appstream | All versions | 0:8.0.40-1.module+el8.2.0+22898+0bdd8c5b.4 | | `mysql-debugsource` | Red Hat:rhel_aus:8.2::appstream | All versions | 0:8.0.40-1.module+el8.2.0+22898+0bdd8c5b.4 | | `mysql-devel` | Red Hat:rhel_aus:8.2::appstream | All versions | 0:8.0.40-1.module+el8.2.0+22898+0bdd8c5b.4 | | `mysql-devel-debuginfo` | Red Hat:rhel_aus:8.2::appstream | All versions | 0:8.0.40-1.module+el8.2.0+22898+0bdd8c5b.4 | | `mysql-errmsg` | Red Hat:rhel_aus:8.2::appstream | All versions | 0:8.0.40-1.module+el8.2.0+22898+0bdd8c5b.4 | | `mysql-libs` | Red Hat:rhel_aus:8.2::appstream | All versions | 0:8.0.40-1.module+el8.2.0+22898+0bdd8c5b.4 | | `mysql-libs-debuginfo` | Red Hat:rhel_aus:8.2::appstream | All versions | 0:8.0.40-1.module+el8.2.0+22898+0bdd8c5b.4 | | `mysql-server` | Red Hat:rhel_aus:8.2::appstream | All versions | 0:8.0.40-1.module+el8.2.0+22898+0bdd8c5b.4 | | `mysql-server-debuginfo` | Red Hat:rhel_aus:8.2::appstream | All versions | 0:8.0.40-1.module+el8.2.0+22898+0bdd8c5b.4 | | `mysql-test` | Red Hat:rhel_aus:8.2::appstream | All versions | 0:8.0.40-1.module+el8.2.0+22898+0bdd8c5b.4 | | `mysql-test-debuginfo` | Red Hat:rhel_aus:8.2::appstream | All versions | 0:8.0.40-1.module+el8.2.0+22898+0bdd8c5b.4 | | `mecab` | Red Hat:rhel_aus:8.4::appstream | All versions | 0:0.996-1.module+el8.0.0+3898+e09bb8de.9 | | `mecab-debuginfo` | Red Hat:rhel_aus:8.4::appstream | All versions | 0:0.996-1.module+el8.0.0+3898+e09bb8de.9 | | `mecab-debugsource` | Red Hat:rhel_aus:8.4::appstream | All versions | 0:0.996-1.module+el8.0.0+3898+e09bb8de.9 | | `mecab-ipadic` | Red Hat:rhel_aus:8.4::appstream | All versions | 0:2.7.0.20070801-16.module+el8.0.0+3898+e09bb8de | | `mecab-ipadic-EUCJP` | Red Hat:rhel_aus:8.4::appstream | All versions | 0:2.7.0.20070801-16.module+el8.0.0+3898+e09bb8de | | `mysql` | Red Hat:rhel_aus:8.4::appstream | All versions | 0:8.0.40-1.module+el8.4.0+22899+4f2ca788.1 | | `mysql-common` | Red Hat:rhel_aus:8.4::appstream | All versions | 0:8.0.40-1.module+el8.4.0+22899+4f2ca788.1 | | `mysql-debuginfo` | Red Hat:rhel_aus:8.4::appstream | All versions | 0:8.0.40-1.module+el8.4.0+22899+4f2ca788.1 | Products: Oracle Mysql Server. ## How do I fix CVE-2025-21521? Apply the vendor's patch. ## Is CVE-2025-21521 being exploited? There is no known exploitation of CVE-2025-21521 in the wild and no public exploit code. ## Other vulnerabilities in Oracle Mysql Server - [CVE-2023-21912](https://insights.sbomify.com/CVE-2023-21912/): Denial of service in MySQL Server (high 7.5) - [CVE-2026-22009](https://insights.sbomify.com/CVE-2026-22009/): Denial of service in MySQL Server (medium 6.5) - [CVE-2026-22017](https://insights.sbomify.com/CVE-2026-22017/): Denial of service in MySQL Server (medium 6.5) - [CVE-2026-34270](https://insights.sbomify.com/CVE-2026-34270/): Denial of service in MySQL Server (medium 6.5) - [CVE-2026-34271](https://insights.sbomify.com/CVE-2026-34271/): Denial of service in MySQL Server (medium 6.5) ## Fix prompt for AI coding agents ```text Check this codebase for CVE-2025-21521 and fix it if it is affected. What it is: CVE-2025-21521 is a high-severity denial of service vulnerability in Oracle Mysql Server, published on 21 Jan 2025. An attacker can exploit it over the internet without logging in, with no action from the victim. Exploitation: There is no known exploitation of CVE-2025-21521 in the wild and no public exploit code. Affected product: Oracle Mysql Server. 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-2025-21521/ (Markdown: https://insights.sbomify.com/CVE-2025-21521/index.md) ``` ## Sources - CVE record: https://www.cve.org/CVERecord?id=CVE-2025-21521 - NVD: https://nvd.nist.gov/vuln/detail/CVE-2025-21521 - OSV: https://osv.dev/vulnerability/CVE-2025-21521 --- From sbomify Insights: https://insights.sbomify.com/CVE-2025-21521/ Summaries are generated and may contain mistakes; the official description above is the record.