Summary
AsyncHttpClient: Cookie Domain attribute is not checked against the public suffix list, so a cookie can be set for co.uk
Affected versions
- 3.x: up to and including 3.0.12
- 2.x: up to and including 2.16.0
Relationship to CVE-2026-55688
CVE-2026-55688 (GHSA-m452-q8c9-rg2f) covered the direct form of this, where a host sets a Domain naming an unrelated host, and that form is genuinely fixed: attacker.co.uk can no longer set Domain=bank.co.uk, and this was verified as a control. What that fix did not add is the public suffix test, so setting Domain=co.uk still reaches bank.co.uk. This advisory covers only the residual.
Workarounds
Do not share one CookieStore across origins that are not mutually trusted. Supplying a CookieStore implementation that rejects Domain values which are public suffixes also avoids it.
Details
ThreadSafeCookieStore.domainsMatch is requestDomain.equals(cookieDomain) || requestDomain.endsWith('.' + cookieDomain). It is used both to accept a Domain on storage and to select cookies for a request, and neither call site consults a public suffix list. A search of the client for any public suffix or effective TLD handling returns nothing.
Impact
The cookie store decides whether a Domain attribute may be accepted using only the domain-matching rule of RFC 6265 Section 5.1.3, which asks whether the request host is the domain or ends with a dot followed by it. Section 5.3 step 5, which additionally requires rejecting a Domain that is a public suffix, is not implemented anywhere in the client.
So a host under a multi-label public suffix can set a cookie for the suffix itself, and the store then hands it to every other host under that suffix:
attacker.co.uk -> Set-Cookie: SID=attacker-value; Domain=co.uk; Path=/
bank.co.uk -> Cookie: SID=attacker-value
Domain=uk works the same way. The attacker needs only a site under the same suffix as the victim, which for suffixes such as co.uk, com.au, or github.io is trivially obtainable.
Depending on what the application does with the cookie, this is session fixation, or it overwrites a session the victim site set, or it lets the attacker plant a value the victim site trusts.
Affected versions
Security releases
Kodem intelligence
Severity tells you how bad this could be in the worst case. It does not tell you whether you are exposed. Exploitability and impact are functions of runtime truth: whether the vulnerable code is present, reachable, and actually executes in your application. A vulnerable package can sit in your dependency tree and never run.
Kodem, an Intelligent Application Security platform, uses runtime intelligence to reveal which vulnerabilities actually execute in production, so teams prioritize the ones that genuinely matter. Kodem's runtime-powered SCA identifies whether this CVE is reachable in your applications.
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Fixed in 3.0.13 on the 3.x line. The ICANN section of the Mozilla public suffix list is bundled with the client and a Domain matching it is rejected, honouring the list's wildcard and exception rules. The list is data and goes stale, so a suffix added upstream after a release is not recognised until the bundled copy is refreshed. The 2.x line is not yet fixed.
Frequently Asked Questions
- What is CVE-2026-107280? CVE-2026-107280 is a medium-severity security vulnerability in org.asynchttpclient:async-http-client (maven), affecting versions >= 3.0.0, <= 3.0.12. It is fixed in 3.0.13, 2.16.1.
- Which versions of org.asynchttpclient:async-http-client are affected by CVE-2026-107280? org.asynchttpclient:async-http-client (maven) versions >= 3.0.0, <= 3.0.12 is affected.
- Is there a fix for CVE-2026-107280? Yes. CVE-2026-107280 is fixed in 3.0.13, 2.16.1. Upgrade to this version or later.
- Is CVE-2026-107280 exploitable, and should I be worried? Whether CVE-2026-107280 is exploitable in your environment depends on whether the vulnerable code is present and reachable. A CVSS score is a worst-case rating; it does not account for your specific deployment, configuration, or usage patterns. Kodem, an Intelligent Application Security platform, uses runtime intelligence to show which vulnerabilities actually execute in production, so you can focus on the ones that represent real risk. Get a demo
- What actually determines whether CVE-2026-107280 is exploitable, and how bad it is? Exploitability and impact are not fixed properties of a CVE. They depend on runtime truth: whether the vulnerable code is present, reachable, and actually executes in your application. A high CVSS score on a dependency that never runs is not the same as real risk. Kodem, an Intelligent Application Security platform, uses runtime intelligence to reveal which vulnerabilities actually execute in production, so teams prioritize the ones that genuinely matter.
- How do I fix CVE-2026-107280?
- Upgrade
org.asynchttpclient:async-http-clientto 3.0.13 or later - Upgrade
org.asynchttpclient:async-http-clientto 2.16.1 or later
- Upgrade