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AsyncHttpClient stores cookie for an unrelated domain (cookie tossing) via ThreadSafeCookieStore

Moderate severity GitHub Reviewed Published Jun 15, 2026 in AsyncHttpClient/async-http-client • Updated Aug 26, 2026

Package

maven org.asynchttpclient:async-http-client (Maven)

Affected versions

>= 3.0.0.Beta1, < 3.0.11
>= 2.0.0, < 2.16.0

Patched versions

3.0.11
2.16.0

Description

Impact

A cookie tossing / cookie injection issue (CWE-1275). 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 (RFC 6265 §5.3 step 6). 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.

Who is Impacted

Applications that use a single AsyncHttpClient instance - and thus the default, shared CookieStore - to reach both an attacker-influenced host and a trusted host. Typical exposure: crawlers, link-preview / webhook fetchers, SSRF-style "fetch this URL" features, multi-backend aggregators, or following redirects to an attacker-controlled host. The attacker can write a cookie the client presents to the victim host (session fixation, overwriting a session id / CSRF-token cookie); they cannot read the victim host's cookies. Applications that talk only to a fixed trusted backend, or that disable/scope the cookie store, are not exposed.

Patches

Fixed in 3.0.11 and 2.16.0

Workarounds

  • Disable the cookie store (setCookieStore(null)) when cookies are not needed; or
  • Use a separate AsyncHttpClient (separate cookie store) per trust domain so an attacker-influenced host and a trusted host never share a jar
  • Supply a custom CookieStore whose add(Uri, Cookie) rejects cookies whose Domain is not domain-matched by the request host.

References

@hyperxpro hyperxpro published to AsyncHttpClient/async-http-client Jun 15, 2026
Published by the National Vulnerability Database Jul 1, 2026
Published to the GitHub Advisory Database Aug 26, 2026
Reviewed Aug 26, 2026
Last updated Aug 26, 2026

Severity

Moderate

CVSS overall score

This score calculates overall vulnerability severity from 0 to 10 and is based on the Common Vulnerability Scoring System (CVSS).
/ 10

CVSS v3 base metrics

Attack vector
Network
Attack complexity
High
Privileges required
None
User interaction
None
Scope
Changed
Confidentiality
None
Integrity
Low
Availability
None

CVSS v3 base metrics

Attack vector: More severe the more the remote (logically and physically) an attacker can be in order to exploit the vulnerability.
Attack complexity: More severe for the least complex attacks.
Privileges required: More severe if no privileges are required.
User interaction: More severe when no user interaction is required.
Scope: More severe when a scope change occurs, e.g. one vulnerable component impacts resources in components beyond its security scope.
Confidentiality: More severe when loss of data confidentiality is highest, measuring the level of data access available to an unauthorized user.
Integrity: More severe when loss of data integrity is the highest, measuring the consequence of data modification possible by an unauthorized user.
Availability: More severe when the loss of impacted component availability is highest.
CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:C/C:N/I:L/A:N

EPSS score

Exploit Prediction Scoring System (EPSS)

This score estimates the probability of this vulnerability being exploited within the next 30 days. Data provided by FIRST.
(25th percentile)

Weaknesses

Sensitive Cookie with Improper SameSite Attribute

The SameSite attribute for sensitive cookies is not set, or an insecure value is used. Learn more on MITRE.

CVE ID

CVE-2026-55688

GHSA ID

GHSA-m452-q8c9-rg2f

Source code

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