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RedisDatabase / datastore

CVE-2025-21605

HIGH · 7.5 CVSS v3.1 Published 2025-04-23
Fix available
A fix is available. Upgrade to 6.2.18 / 7.2.8 or later.
See remediation →
84/100
Remediation priority · High
Remotely reachable No privileges Zero-click

Official description Straight from the sourceThe vendor's or NVD's own wording, published unedited. Authoritative, but often terse — it says what broke, rarely what to do.

NVD · unedited
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.

Technical summary Written by usOur analysis, written from the advisory, the CVSS vector and the affected-version data. It adds context the advisory leaves out, and never invents facts that are not in the source.

dbcve analysis · high confidence

Unauthenticated Redis clients can cause unlimited growth of output buffers by triggering large responses (including NOAUTH authentication error messages), leading to memory exhaustion. Versions 2.6 through 7.4.2 are affected; the default client-output-buffer-limit configuration allows normal clients to grow buffers without restriction.

MitigationUpgrade Redis to version 7.4.3 or later, which includes the patch for this vulnerability. As a compensating control, implement network-level access restrictions (firewalls, iptables, or TLS with client certificate authentication) to block unauthenticated access.

Verify against the referenced sources before acting — the references below are authoritative for this CVE, this summary is not.

Affected products & versions What the vendor confirmedThe version ranges the vendor confirmed as vulnerable. If your version sits inside a range here, treat yourself as exposed until you have upgraded.

NVD · CPE data
RedisDatabase / datastore
Affected:>= 2.6.0, < 6.2.18>= 7.0, < 7.2.8>= 7.4.0, < 7.4.3
Debian LinuxOperating system
Affected:= 11.0
ValkeyApplication
Affected:>= 7.2.4, < 7.2.9>= 8.0.0, < 8.0.3>= 8.1.0, < 8.1.1

CVSS breakdown How the score is builtThe industry scoring standard. It rates how the flaw is reached, what it takes to exploit, and what an attacker gains — the score is derived from those, not the other way round.

From the vector
Attack vector
Network
Complexity
Low
Privileges
None
User interaction
None
Scope
Unchanged
Confidentiality
None
Integrity
None
Availability
High

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

Am I affected? How to checkSteps we derive from the advisory and the affected-version data, so you can decide whether this CVE reaches your setup. They are a guide, not a scan — your own configuration is the authority.

dbcve checks

Work through these to decide whether this CVE applies to you.

  1. Identify the installed Redis or Valkey version
    Run `redis-server --version` or `valkey-server --version` to see the exact version number
    Affected if The version falls within any of these ranges: >= 2.6.0 and < 6.2.18, >= 7.0 and < 7.2.8, >= 7.4.0 and < 7.4.3 (for Redis); >= 7.2.4 and < 7.2.9, >= 8.0.0 and < 8.0.3, >= 8.1.0 and < 8.1.1 (for Valkey)
  2. Check if the server is reachable without authentication
    Run `redis-cli ping` or `nc -zv <host> 6379` from an untrusted network location, or check the `protected-mode` and `bind` settings in the config file
    Affected if The server responds to unauthenticated connections (protected-mode is set to no, or bind allows external access without requirepass being set)
  3. Inspect the client-output-buffer-limit configuration
    Run `redis-cli CONFIG GET client-output-buffer-limit` to see the current buffer limit settings
    Affected if The default limits are in use and allow normal clients to grow buffers without restriction (limits are set to 0 or very high values)
  4. Verify memory usage growth pattern
    Monitor the Redis process memory usage over time with `redis-cli INFO memory` or system tools like `ps` or `top` while allowing unauthenticated connections
    Affected if Memory usage continuously grows without bound when clients connect and trigger responses, including authentication error messages

You are affected if you run a vulnerable Redis/Valkey version (2.6.0 to 7.4.2 for Redis, 7.2.4 to 8.1.1 for Valkey) AND the server accepts unauthenticated connections, allowing clients to trigger unbounded output buffer growth leading to memory exhaustion.

Generated from the published advisory. Verify against your own configuration.

Check your environment

Paste your version and any relevant configuration and it will be compared against the affected criteria above. Do not include secrets or credentials.

AI-assisted, checked against the advisory. Informational, not a guarantee.

Remediation Closing itWhat it takes to close this. Where a vendor fix exists we point at it; where none exists we say so plainly, and can build one. Effort estimates are scoped from the advisory, not from your codebase.

dbcve · scoped
Upgrade available Upgrade to 6.2.18 / 7.2.8 / 7.2.9 or later
Fixed in 6.2.187.2.87.2.9
Interim mitigation

Upgrade Redis to version 7.4.3 or later, which includes the patch for this vulnerability. As a compensating control, implement network-level access restrictions (firewalls, iptables, or TLS with client certificate authentication) to block unauthenticated access.

Recommended fix High confidence

Redis: 6.2.18, 7.2.8, or 7.4.3 depending on current branch; Valkey: 7.2.9, 8.0.3, or 8.1.1 depending on current branch; Debian: install latest redis security updates

  1. 1. Identify current Redis or Valkey version by running 'redis-server --version' or 'valkey-server --version'
  2. 2. For Redis users: If version is < 6.2.18, upgrade to 6.2.18 or later; if 7.0-7.2.x, upgrade to 7.2.8 or later; if 7.4.0-7.4.2, upgrade to 7.4.3
  3. 3. For Valkey users: If version is 7.2.4-7.2.8, upgrade to 7.2.9; if 8.0.0-8.0.2, upgrade to 8.0.3; if 8.1.0, upgrade to 8.1.1
  4. 4. For Debian 11 systems: Apply Debian security updates for the redis package via 'apt update && apt upgrade redis-server'
  5. 5. After upgrade, verify the new version is running: 'redis-server --version' or 'valkey-server --version'
  6. 6. Restart the Redis/Valkey service: 'systemctl restart redis-server' or 'systemctl restart valkey-server'
  7. 7. If immediate patching is not possible, mitigate by restricting network access: configure firewall/iptables to allow only trusted IPs on Redis port (default 6379), or enable requirepass and TLS client certificates
Caveat Review release notes for your version branch for any potential breaking changes before upgrading in production; test upgrade in staging environment first

Generated from the published advisory — verify against the referenced sources before acting.

Fix this in Redis Scoped from the published advisory
  • Consultation2.0 h
  • Implementation4.0 h
  • Testing3.0 h
  • Review / QA1.0 h
10.0 hours of engineering $1,750
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References Go to the primary sourcePrimary sources — vendor advisories, patches and trackers. Where our summary and a reference disagree, the reference wins.

Primary sources

Practitioner notes

Contributed

Peer-ranked notes from engineers who’ve handled CVE-2025-21605 in production — separate from our analysis above.

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What this is

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What belongs here
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