CVE-2026-55688Network attack vector

Cross-domain cookie injection via unchecked Domain attribute

Published Jul 1, 2026 · Updated Jul 1, 2026

Cookie injection in Async Http Client 2.x before 2.16.0 and 3.x before 3.0.11 allows remote attackers to plant cross-domain cookies. ThreadSafeCookieStore.add stores a response cookie under its Domain attribute without verifying that the request host domain-matches that scope. Exploitation requires one default shared CookieStore to contact both an attacker-influenced host and a trusted host; planted cookies are sent to the trusted host, but its cookies are not disclosed.

CVSS severity4.0
Medium
EPSS probability0.33%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Cookie injection in Async Http Client 2.x before 2.16.0 and 3.x before 3.0.11 allows remote attackers to plant cross-domain cookies. ThreadSafeCookieStore.add stores a response cookie under its Domain attribute without verifying that the request host domain-matches that scope. Exploitation requires one default shared CookieStore to contact both an attacker-influenced host and a trusted host; planted cookies are sent to the trusted host, but its cookies are not disclosed.

The record

CVE
CVE-2026-55688
Published
Jul 1, 2026
Updated
Jul 1, 2026
Vendor
AsyncHttpClient
Product
Async Http Client
Classifications
CWE-1275
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Jul 1, 2026CVE publishedPublication date reported by the CVE source.
  2. Jul 1, 2026Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

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Is a vulnerable build present?

Compare these published version ranges with your installed build and any vendor patches.

  1. Affected versionversion=>= 2.0.0, < 2.16.0
  2. Affected versionversion=>= 3.0.0.Beta1, < 3.0.11

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

AsyncHttpClient · Async Http Clientversion=>= 2.0.0, < 2.16.0; version=>= 3.0.0.Beta1, < 3.0.11

Published CVSS scores

4.0GitHubCVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:C/C:N/I:L/A:N

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

Daily unique IPsNo honeypot observations are available for this CVE in the selected window.

No observations available

Sep 10, 2026Sep 16, 2026
Latest reporting daySep 16, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-1275Sensitive Cookie with Improper SameSite Attribute

Public exploit references

No public exploit references are available in this record.

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Technologies

Your stack

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Your stack

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