CVE-2026-102740: AsyncHttpClient: Resumable download index store is created world-readable and follows a planted symlink
The AsyncHttpClient library allows Java applications to execute HTTP requests and asynchronously process HTTP responses. From 2.0.0 until 2.16.1 and 3.0.12, PropertiesBasedResumableProcessor stores resumable download state at the predictable shared path $java.io.tmpdir/ahc/ResumableAsyncHandler.properties with default permissions and link-following file operations. A local user who can read the shared store can see download URLs, including embedded user information or query tokens. A local user who can write within or pre-create the affected shared store directory can plant a symbolic link that the client follows when saving state, truncating and overwriting a target file writable by the client process. The filesystem path is used when ResumableAsyncHandler decorates another AsyncHandler, while the no-argument constructors use a no-op processor and are unaffected. This issue is fixed in versions 2.16.1 and 3.0.12.
Affected Software
Remediation
Recommended actions to resolve this vulnerability, in priority order.
- Upgrade
Upgrade
AsyncHttpClientto a version that resolves this vulnerability.Fixed in 2.16.1 - Upgrade
Upgrade
AsyncHttpClientto a version that resolves this vulnerability.Fixed in 3.0.12
Event History
Frequently Asked Questions
Which applications are exposed to this issue?
Applications are affected only when ResumableAsyncHandler is configured to decorate another AsyncHandler and therefore uses the filesystem-backed resumable state processor. The no-argument constructors use a no-op processor and are unaffected.
What access does an attacker need?
Exploitation requires local access. Reading the shared state store can expose download URLs and embedded credentials or query tokens; overwriting another file requires the local user to be able to write in, or pre-create, the affected shared-store directory and plant a symbolic link.
How can I determine whether an application may be affected?
Check whether the application uses PropertiesBasedResumableProcessor or a ResumableAsyncHandler configuration that persists state under $java.io.tmpdir/ahc/ResumableAsyncHandler.properties. Also review whether other local users can read that store or create/write entries in its directory.
What versions contain the fix?
The issue is fixed in AsyncHttpClient 2.16.1 and 3.0.12. Versions from 2.0.0 through the affected releases should be upgraded to the applicable fixed version.