CVE-2025-21605
Redis DoS Vulnerability due to unlimited growth of output buffers abused by unauthenticated client
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.
INFO
Published Date :
April 23, 2025, 4:15 p.m.
Last Modified :
Sept. 5, 2025, 2:31 p.m.
Remotely Exploit :
Yes !
Source :
[email protected]
Affected Products
The following products are affected by CVE-2025-21605
vulnerability.
Even if cvefeed.io is aware of the exact versions of the
products
that
are
affected, the information is not represented in the table below.
CVSS Scores
| Score | Version | Severity | Vector | Exploitability Score | Impact Score | Source |
|---|---|---|---|---|---|---|
| CVSS 3.1 | HIGH | [email protected] |
Solution
- Update Redis to version 7.4.3 or later.
- Block unauthenticated access to Redis.
- Enable TLS and client certificate authentication.
- Configure network access controls for Redis.
References to Advisories, Solutions, and Tools
Here, you will find a curated list of external links that provide in-depth
information, practical solutions, and valuable tools related to
CVE-2025-21605.
| URL | Resource |
|---|---|
| https://github.com/redis/redis/releases/tag/7.4.3 | Release Notes |
| https://github.com/redis/redis/security/advisories/GHSA-r67f-p999-2gff | Third Party Advisory |
| https://github.com/valkey-io/valkey/releases/tag/8.1.1 | Release Notes |
| https://lists.debian.org/debian-lts-announce/2025/05/msg00014.html | Mailing List |
CWE - Common Weakness Enumeration
While CVE identifies
specific instances of vulnerabilities, CWE categorizes the common flaws or
weaknesses that can lead to vulnerabilities. CVE-2025-21605 is
associated with the following CWEs:
Common Attack Pattern Enumeration and Classification (CAPEC)
Common Attack Pattern Enumeration and Classification
(CAPEC)
stores attack patterns, which are descriptions of the common attributes and
approaches employed by adversaries to exploit the CVE-2025-21605
weaknesses.
We scan GitHub repositories to detect new proof-of-concept exploits. Following list is a collection of public exploits and proof-of-concepts, which have been published on GitHub (sorted by the most recently updated).
Results are limited to the first 15 repositories due to potential performance issues.
The following list is the news that have been mention
CVE-2025-21605 vulnerability anywhere in the article.
-
Cyber Security News
Redis DoS Vulnerability: Attackers Can Exhaust Server Memory or Cause Crashes
A high-severity vulnerability in Redis, the popular open-source in-memory data structure store, that could allow unauthenticated attackers to cause denial-of-service conditions by exhausting server me ... Read more
-
Daily CyberSecurity
Redis Vulnerability Exposes Servers to Denial-of-Service Attacks
A high-severity vulnerability has been discovered in Redis, the popular open-source in-memory data structure store, which could allow unauthenticated users to exhaust server memory and cause a Denial- ... Read more
The following table lists the changes that have been made to the
CVE-2025-21605 vulnerability over time.
Vulnerability history details can be useful for understanding the evolution of a vulnerability, and for identifying the most recent changes that may impact the vulnerability's severity, exploitability, or other characteristics.
-
Initial Analysis by [email protected]
Sep. 05, 2025
Action Type Old Value New Value Added CPE Configuration OR *cpe:2.3:a:redis:redis:*:*:*:*:*:*:*:* versions from (including) 2.6.0 up to (excluding) 7.4.3 Added CPE Configuration OR *cpe:2.3:a:lfprojects:valkey:*:*:*:*:*:*:*:* versions from (including) 8.0.0 up to (excluding) 8.0.3 *cpe:2.3:a:lfprojects:valkey:*:*:*:*:*:*:*:* versions from (including) 8.1.0 up to (excluding) 8.1.1 *cpe:2.3:a:lfprojects:valkey:*:*:*:*:*:*:*:* versions from (including) 7.2.4 up to (excluding) 7.2.9 Added CPE Configuration OR *cpe:2.3:o:debian:debian_linux:11.0:*:*:*:*:*:*:* Added Reference Type GitHub, Inc.: https://github.com/redis/redis/releases/tag/7.4.3 Types: Release Notes Added Reference Type GitHub, Inc.: https://github.com/redis/redis/security/advisories/GHSA-r67f-p999-2gff Types: Third Party Advisory Added Reference Type CVE: https://github.com/valkey-io/valkey/releases/tag/8.1.1 Types: Release Notes Added Reference Type CVE: https://lists.debian.org/debian-lts-announce/2025/05/msg00014.html Types: Mailing List -
CVE Modified by af854a3a-2127-422b-91ae-364da2661108
Jun. 02, 2025
Action Type Old Value New Value Added Reference https://github.com/valkey-io/valkey/releases/tag/8.1.1 -
CVE Modified by af854a3a-2127-422b-91ae-364da2661108
May. 12, 2025
Action Type Old Value New Value Added Reference https://lists.debian.org/debian-lts-announce/2025/05/msg00014.html -
New CVE Received by [email protected]
Apr. 23, 2025
Action Type Old Value New Value Added 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. Added CVSS V3.1 AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H Added CWE CWE-770 Added Reference https://github.com/redis/redis/releases/tag/7.4.3 Added Reference https://github.com/redis/redis/security/advisories/GHSA-r67f-p999-2gff