Bug 2553624 (CVE-2026-102740)

Summary: CVE-2026-102740 org.asynchttpclient/async-http-client: AsyncHttpClient: Arbitrary file overwrite via insecure temporary file handling
Product: [Other] Security Response Reporter: OSIDB Bzimport <bzimport>
Component: vulnerabilityAssignee: Product Security DevOps Team <prodsec-dev>
Status: NEW --- QA Contact:
Severity: medium Docs Contact:
Priority: medium    
Version: unspecifiedCC: gmalinko, janstey, pdelbell, rstepani
Target Milestone: ---Keywords: Security
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Hardware: All   
OS: Linux   
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A flaw was found in AsyncHttpClient. Resumable download state is stored in a predictable shared temporary directory with insecure permissions and link-following file operations. A local attacker can exploit this issue by placing a symbolic link in the shared location to overwrite arbitrary files writable by the application process, or by reading the state file to obtain sensitive download URLs and authentication tokens.
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Description OSIDB Bzimport 2026-10-15 17:32:09 UTC 
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.