CVE-2025-21605
What it is
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.
At a glance
- Exploitability
- Can be exploited over the network without logging in. High risk of service disruption.
- Exploit odds
- 0.9% chance of exploitation in the next 30 days (EPSS).
- Fix
- A patch, advisory or fixed version is referenced. Upgrade or apply it.
Timeline
- PublishedDisclosed publicly on CVE.org and NVD
- Last updatedMost recent change to the record
Why it ranks here
- Exploited in the wild: no, CISA does not list it.
- Exploit odds: 0.9% in the next 30 days (EPSS).
- Severity: 7.5 HIGH (CVSS).
- Fix: a patch or advisory is linked.
Details
- Published
- Last modified
- Exploit probability
- 0.9% · EPSS, next 30 days
- Weakness
- CWE-770 · Allocation without limits
- Record status
- Modified
Affected
- Redis < 6.2.18
- Redis < 7.2.8
- Redis < 7.4.3
- Lfprojects Valkey < 7.2.9
- Lfprojects Valkey < 8.0.3
- Lfprojects Valkey < 8.1.1
- Debian Linux 11.0
Attack profile CVSS 3.1 · 7.5
- Attack vector
- Network
- Complexity
- Low
- Privileges needed
- None
- User interaction
- None
- Scope
- Unchanged
- Confidentiality
- None
- Integrity
- None
- Availability
- High
Raw vector
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
Is it in your code?
Hand this to your coding agent. It searches your project for the affected products and checks versions. Nothing leaves your machine.
Read https://cve-list.com/agent/cve/CVE-2025-21605.md and follow it. Check whether this project is affected by CVE-2025-21605. Read only. Don't change anything and don't upload my code. Tell me yes, no or not sure, with the file as proof.
Fix and advisories
- https://github.com/redis/redis/releases/tag/7.4.3
- https://github.com/redis/redis/security/advisories/GHSA-r67f-p999-2gff
- https://github.com/valkey-io/valkey/releases/tag/8.1.1
References
- https://github.com/redis/redis/releases/tag/7.4.3
- https://github.com/redis/redis/security/advisories/GHSA-r67f-p999-2gff
- https://github.com/valkey-io/valkey/releases/tag/8.1.1
- https://lists.debian.org/debian-lts-announce/2025/05/msg00014.html
- https://www.vicarius.io/vsociety/posts/cve-2025-21605-detection-script-memory-exhaustion-vulnerability-in-redis-database
- https://www.vicarius.io/vsociety/posts/cve-2025-21605-mitigation-script-memory-exhaustion-vulnerability-in-redis-database