# CVE-2025-21605: Redis DoS Vulnerability due to unlimited growth of output buffers abused by unauthenticated client > Unauthenticated clients can exhaust server memory by causing unlimited output buffer growth, leading to service denial. - **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:** 23 Apr 2025 - **Updated:** 10 Feb 2026 - **Also known as:** ALPINE-CVE-2025-21605, ALSA-2025:7429, ALSA-2025:7438, ALSA-2025:7509, ALSA-2025:7686, AZL-60939, BELL-CVE-2025-21605, BIT-keydb-2025-21605, BIT-redis-2025-21605, BIT-valkey-2025-21605, CLEANSTART-2026-MU78346, CLSA-2025-1750785864, DEBIAN-CVE-2025-21605, DLA-4162-1, ECHO-0928-6c8a-5d18, GHSA-r67f-p999-2gff, MGASA-2025-0171, MINI-49r7-mvrc-24jg, MINI-97hc-3f7m-cf56, MINI-mm5q-qq63-f9mq, OESA-2025-1474, RHSA-2025:4441, RHSA-2025:4561, RHSA-2025:4577, RHSA-2025:4607, RHSA-2025:4788, RHSA-2025:4789, RHSA-2025:7429, RHSA-2025:7438, RHSA-2025:7509, RHSA-2025:7538, RHSA-2025:7630, RHSA-2025:7686, RLSA-2025:7429, RLSA-2025:7438, RLSA-2025:7509, RLSA-2025:7686, SUSE-SU-2025:02010-1, SUSE-SU-2025:1419-1, SUSE-SU-2025:1420-1, SUSE-SU-2025:1432-1, SUSE-SU-2025:1433-1, SUSE-SU-2025:1566-1, UBUNTU-CVE-2025-21605, openSUSE-SU-2025:15035-1 ## What is CVE-2025-21605? CVE-2025-21605 is a high-severity denial of service vulnerability in Debian Debian Linux, published on 23 Apr 2025. An attacker can exploit it over the internet without logging in, with no action from the victim. ### Official description Redis is an open source, in-memory database that persists on disk. In versions starting at 2.6 and prior to 7.4.3, An unauthenticated client can cause unlimited growth of output buffers, until the server runs out of memory or is killed. By default, the Redis configuration does not limit the output buffer of normal clients (see client-output-buffer-limit). Therefore, the output buffer can grow unlimitedly over time. As a result, the service is exhausted and the memory is unavailable. When password authentication is enabled on the Redis server, but no password is provided, the client can still cause the output buffer to grow from "NOAUTH" responses until the system will run out of memory. This issue has been patched in version 7.4.3. An additional workaround to mitigate this problem without patching the redis-server executable is to block access to prevent unauthenticated users from connecting to Redis. This can be done in different ways. Either using network access control tools like firewalls, iptables, security groups, etc, or enabling TLS and requiring users to authenticate using client side certificates. Weakness: CWE-770 (Allocation of Resources Without Limits or Throttling) ## Which versions are affected by CVE-2025-21605? 3 open source packages ship an affected version, including keydb, redis and valkey. It affects 3 products. | Package | Ecosystem | Affected | Fixed in | | --- | --- | --- | --- | | `keydb` | Bitnami | From 2.6.0 | 6.2.18, 7.2.8, 7.4.3 | | `redis` | Bitnami | From 2.6.0 | 6.2.18, 7.2.8, 6.2.18, 7.2.8, 7.4.3 | | `valkey` | Bitnami | All versions | 7.2.9, 8.0.3, 8.1.1 | | `valkey` | AlmaLinux:10 | All versions | 8.0.3-1.el10_0 | | `valkey-devel` | AlmaLinux:10 | All versions | 8.0.3-1.el10_0 | | `redis` | AlmaLinux:8 | All versions | 6.2.18-1.module_el8.10.0+3994+c2cc5395 | | `redis-devel` | AlmaLinux:8 | All versions | 6.2.18-1.module_el8.10.0+3994+c2cc5395 | | `redis-doc` | AlmaLinux:8 | All versions | 6.2.18-1.module_el8.10.0+3994+c2cc5395 | | `redis` | AlmaLinux:9 | All versions | 6.2.18-1.el9_6 | | `redis` | AlmaLinux:9 | All versions | 7.2.8-1.module_el9.6.0+168+b8d8e900 | | `redis-devel` | AlmaLinux:9 | All versions | 6.2.18-1.el9_6 | | `redis-devel` | AlmaLinux:9 | All versions | 7.2.8-1.module_el9.6.0+168+b8d8e900 | | `redis-doc` | AlmaLinux:9 | All versions | 6.2.18-1.el9_6 | | `redis-doc` | AlmaLinux:9 | All versions | 7.2.8-1.module_el9.6.0+168+b8d8e900 | | `discovery-cli` | Red Hat:discovery:1.0::el8 | All versions | 0:1.14.0-1.el8 | | `discovery-installer` | Red Hat:discovery:1.0::el8 | All versions | 0:1.14.1-1.el8 | | `discovery-cli` | Red Hat:discovery:1.0::el9 | All versions | 0:1.14.0-1.el9 | | `discovery-installer` | Red Hat:discovery:1.0::el9 | All versions | 0:1.14.1-1.el9 | | `valkey` | Red Hat:enterprise_linux:10.0 | All versions | 0:8.0.3-1.el10_0 | | `valkey-debuginfo` | Red Hat:enterprise_linux:10.0 | All versions | 0:8.0.3-1.el10_0 | | `valkey-debugsource` | Red Hat:enterprise_linux:10.0 | All versions | 0:8.0.3-1.el10_0 | | `valkey-devel` | Red Hat:enterprise_linux:10.0 | All versions | 0:8.0.3-1.el10_0 | | `redis` | Red Hat:enterprise_linux:8::appstream | All versions | 0:6.2.18-1.module+el8.10.0+23050+05ea4e95 | | `redis-debuginfo` | Red Hat:enterprise_linux:8::appstream | All versions | 0:6.2.18-1.module+el8.10.0+23050+05ea4e95 | | `redis-debugsource` | Red Hat:enterprise_linux:8::appstream | All versions | 0:6.2.18-1.module+el8.10.0+23050+05ea4e95 | | `redis-devel` | Red Hat:enterprise_linux:8::appstream | All versions | 0:6.2.18-1.module+el8.10.0+23050+05ea4e95 | | `redis-doc` | Red Hat:enterprise_linux:8::appstream | All versions | 0:6.2.18-1.module+el8.10.0+23050+05ea4e95 | | `redis` | Red Hat:enterprise_linux:9::appstream | All versions | 0:6.2.18-1.el9_6 | | `redis` | Red Hat:enterprise_linux:9::appstream | All versions | 0:7.2.8-1.module+el9.6.0+23049+8374f320 | | `redis-debuginfo` | Red Hat:enterprise_linux:9::appstream | All versions | 0:6.2.18-1.el9_6 | | `redis-debuginfo` | Red Hat:enterprise_linux:9::appstream | All versions | 0:7.2.8-1.module+el9.6.0+23049+8374f320 | | `redis-debugsource` | Red Hat:enterprise_linux:9::appstream | All versions | 0:6.2.18-1.el9_6 | | `redis-debugsource` | Red Hat:enterprise_linux:9::appstream | All versions | 0:7.2.8-1.module+el9.6.0+23049+8374f320 | | `redis-devel` | Red Hat:enterprise_linux:9::appstream | All versions | 0:6.2.18-1.el9_6 | | `redis-devel` | Red Hat:enterprise_linux:9::appstream | All versions | 0:7.2.8-1.module+el9.6.0+23049+8374f320 | | `redis-doc` | Red Hat:enterprise_linux:9::appstream | All versions | 0:6.2.18-1.el9_6 | | `redis-doc` | Red Hat:enterprise_linux:9::appstream | All versions | 0:7.2.8-1.module+el9.6.0+23049+8374f320 | | `redis` | Red Hat:rhel_aus:8.4::appstream | All versions | 0:6.0.9-5.module+el8.4.0+23067+0d16e377.2 | | `redis-debuginfo` | Red Hat:rhel_aus:8.4::appstream | All versions | 0:6.0.9-5.module+el8.4.0+23067+0d16e377.2 | | `redis-debugsource` | Red Hat:rhel_aus:8.4::appstream | All versions | 0:6.0.9-5.module+el8.4.0+23067+0d16e377.2 | Products: Debian Debian Linux, Lfprojects Valkey, Redis Redis. ## How do I fix CVE-2025-21605? Upgrade keydb to a fixed version for your release line: 6.2.18, 7.2.8 or 7.4.3. ## Is CVE-2025-21605 being exploited? There is no known exploitation of CVE-2025-21605 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-2025-21605 and fix it if it is affected. What it is: CVE-2025-21605 is a high-severity denial of service vulnerability in Debian Debian Linux, published on 23 Apr 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-2025-21605 in the wild and no public exploit code. Affected packages and fixed versions: - keydb (Bitnami): affected from 2.6.0; fixed in 6.2.18, 7.2.8, 7.4.3 - redis (Bitnami): affected from 2.6.0; fixed in 6.2.18, 7.2.8, 6.2.18, 7.2.8, 7.4.3 - valkey (Bitnami): affected all versions; fixed in 7.2.9, 8.0.3, 8.1.1 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-2025-21605/ (Markdown: https://insights.sbomify.com/CVE-2025-21605/index.md) ``` ## Sources - CVE record: https://www.cve.org/CVERecord?id=CVE-2025-21605 - NVD: https://nvd.nist.gov/vuln/detail/CVE-2025-21605 - OSV: https://osv.dev/vulnerability/CVE-2025-21605 --- From sbomify Insights: https://insights.sbomify.com/CVE-2025-21605/ Summaries are generated and may contain mistakes; the official description above is the record.