CVE-2026-55688 AsyncHttpClient: Cookie stored for an unrelated domain (cookie tossing) via ThreadSafeCookieStore
Attackers can inject cookies for unrelated domains via AsyncHttpClient, potentially bypassing security controls in applications sharing a client instance.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Over the internet
- Victim action needed
- Not needed
- Fix
- Available
What is CVE-2026-55688?
CVE-2026-55688 is a medium-severity vulnerability in AsyncHttpClient async-http-client, published on 1 Jul 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.
Official 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.
Weakness: CWE-1275
Which versions are affected by CVE-2026-55688?
4 open source packages ship an affected version, including org.asynchttpclient:async-http-client.
| Package | Affected | Fixed in |
|---|---|---|
org.asynchttpclient:async-http-client Maven | From 2.0.0 | 2.16.0 |
org.asynchttpclient:async-http-client Maven | From 2.0.0 | 2.16.0 |
org.asynchttpclient:async-http-client Maven | From 3.0.0.Beta1 | 3.0.11 |
org.asynchttpclient:async-http-client Maven | From 3.0.0.Beta1 | 3.0.11 |
How do I fix CVE-2026-55688?
Upgrade org.asynchttpclient:async-http-client to a fixed version for your release line: 2.16.0 or 3.0.11.
Is CVE-2026-55688 being exploited?
There is no known exploitation of CVE-2026-55688 in the wild and no public exploit code.
Sources
Also known as DEBIAN-CVE-2026-55688, ECHO-b895-5a76-be10, GHSA-m452-q8c9-rg2f, MINI-4w5m-f4hh-f9qh, MINI-58qp-7ffq-g6vq, MINI-f4gg-r526-v4fc and 3 more.