CVE-2021-20293Network attack vector

Reflected XSS via mishandled path-parameter encoding

Published Jun 10, 2021 · Updated Aug 3, 2024

Reflected XSS in Red Hat RESTEasy 4.6.0.Final and earlier allows remote attackers to execute script via crafted path parameters. When a resource uses @PathParam without declaring an @Produces media type, RESTEasy mishandles URL encoding before reflecting attacker-controlled path data into the response. Exploitation requires a crafted request to reach such an endpoint and user interaction with the reflected response, enabling script execution in the user's browser.

CVSS severity6.1
Medium
EPSS probability0.86%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
Coverage for this vulnerability

See if you're affected

Explore vulnerability checks for your environment with Hinoki.

Book a demo

Summary

What happened

Reflected XSS in Red Hat RESTEasy 4.6.0.Final and earlier allows remote attackers to execute script via crafted path parameters. When a resource uses @PathParam without declaring an @Produces media type, RESTEasy mishandles URL encoding before reflecting attacker-controlled path data into the response. Exploitation requires a crafted request to reach such an endpoint and user interaction with the reflected response, enabling script execution in the user's browser.

The record

CVE
CVE-2021-20293
Published
Jun 10, 2021
Updated
Aug 3, 2024
Vendor
Red Hat
Product
RESTEasy
Classifications
CWE-79, T1203
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Jun 10, 2021CVE publishedPublication date reported by the CVE source.
  2. Aug 3, 2024Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

Compare your product and version with the public record. A matching version still requires validation against your environment.

Is a vulnerable build present?

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

  1. Affected versionversion=All versions of RESTEasy up to 4.6.0.Final

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

Red Hat · RESTEasyversion=All versions of RESTEasy up to 4.6.0.Final

Published CVSS scores

4.3NIST NVDAV:N/AC:M/Au:N/C:N/I:P/A:N
6.1NIST NVDCVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/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-79Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting')
T1203Exploitation for Client Execution

Public exploit references

No public exploit references are available in this record.

Labels summarize the accepted research assessment. They do not indicate a test against your environment.

Technologies

Your stack

See the directory against your own environment.

Your stack

Check the software in your environment

Book a demo to see how Hinoki identifies affected software and validates exploitability in your environment.

Book a demo