Answer in brief
CVE-2021-21342 records a Medium severity (CVSS 5.3) vulnerability in A Server-Side Forgery Request can be activated unmarshalling with XStream to access data streams from an arbitrary URL referencing a resource in an intranet or the local host. The current sources do not mark it as known exploited. The current feed maps x-stream/xstream (generic), com.thoughtworks.xstream:xstream (maven). Check affected ranges and fixed versions before updating.
Analysis pending evidence review
HOL Guard separates source facts from reviewed analysis. See the methodology.
CVSS is 5.3. The current sources do not mark it as known exploited. Treat this as a source-backed prioritization signal, not a statement about your environment.
Analysis status
Analysis pending evidence review
Factual feed record only; HOL analysis is not approved for indexing. Read the methodology.
The current feed maps x-stream/xstream (generic), com.thoughtworks.xstream:xstream (maven). Check affected ranges and fixed versions before updating.
| Package | Affected range | Fixed version |
|---|---|---|
| x-stream/xstreamgeneric | <1.4.16 | 1.4.16 |
| com.thoughtworks.xstream:xstreammaven | >=0 <1.4.16 | 1.4.16 |
Published upstream
Mar 22, 2021
Evidence: source:cvelist:source_dates:source-dates:recordSource modified
Oct 7, 2026
Evidence: source:cvelist:source_dates:source-dates:recordFirst seen by HOL
Aug 8, 2026
XStream is a Java library to serialize objects to XML and back again. In XStream before version 1.4.16, there is a vulnerability where the processed stream at unmarshalling time contains type information to recreate the formerly written objects. XStream creates therefore new instances based on these type information. An attacker can manipulate the processed input stream and replace or inject objects, that result in a server-side forgery request. No user is affected, who followed the recommendation to setup XStream's security framework with a whitelist limited to the minimal required types. If you rely on XStream's default blacklist of the Security Framework, you will have to use at least version 1.4.16.
Quoted source text, attributed separately from HOL analysis.