CVE-2021-4296 | w3c Unicorn ValidatorNuMessage.java ValidatorNuMessage cross site scripting

A vulnerability, which was classified as problematic, has been found in w3c Unicorn. This issue affects the function ValidatorNuMessage of the file src/org/w3c/unicorn/response/impl/ValidatorNuMessage.java. The manipulation of the argument message leads to cross site scripting. The attack may be initiated remotely. The name of the patch is 51f75c31f7fc33859a9a571311c67ae4e95d9c68. It is recommended to apply a patch to fix this issue. The associated identifier of this vulnerability is VDB-217019.

Published: 2022-12-29 Last update: 2024-11-21 Assigner: [email protected] Source: [email protected]
NVD Status：Modified，CVE State: published
View at NVD, CVE.org, EUVD

CVE-2021-4296 is rated Low Risk (31.5/100): CVSS Low severity, with medium exploitation likelihood (EPSS 0.27%). Monitor for updates and reassess as exploit intelligence or EPSS changes.

Risk is dynamic; we continuously reassess and refresh what is shown on this page as upstream context changes.

Exploit prediction scoring system (EPSS) score for CVE-2021-4296

EPSS lead: Daily EPSS estimates relative likelihood of exploitation; percentile ranks this CVE among scored vulnerabilities (higher = more severe relative rank).

# Date Old EPSS score New EPSS score Delta (New - Old)
1 2026-01-07 0.39% 0.27% -0.12%
2 2025-12-30 0.09% 0.39% +0.30%
3 2025-11-21 — 0.09% —

Full EPSS history (7 records total)

Common vulnerability scoring system (CVSS) metrics for CVE-2021-4296

CVSS metrics for this CVE.

Base score Version Severity Vector Exploitability Impact Score source
3.5 3.1 LOW
CVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:U/C:N/I:L/A:N Click to expand
Attack vector (AV:N)
Could be attacked over the internet or any normal routed network—not just someone sitting at the machine.
Attack complexity (AC:L)
Once they can reach the bug, pulling it off is straightforward—no weird race conditions or rare setup.
Privileges required (PR:L)
A normal user session is enough; they don’t have to be admin.
User interaction (UI:R)
A real person has to do something—click, install, enable—otherwise it doesn’t land.
Scope (S:U)
Damage stays in the same “trust bubble” as the broken component—no big spill into unrelated systems.
Confidentiality (C:N)
Doesn’t really leak secrets in a meaningful way.
Integrity (I:L)
Attackers could change some data, but it’s limited—not everything goes.
Availability (A:N)
Service keeps running; no real outage angle.
 2.1 1.4 [email protected]
6.1 3.1 MEDIUM
CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N Click to expand
Attack vector (AV:N)
Could be attacked over the internet or any normal routed network—not just someone sitting at the machine.
Attack complexity (AC:L)
Once they can reach the bug, pulling it off is straightforward—no weird race conditions or rare setup.
Privileges required (PR:N)
No account or special rights needed—anonymous or random user is enough.
User interaction (UI:R)
A real person has to do something—click, install, enable—otherwise it doesn’t land.
Scope (S:C)
Breaking this can reach past the original component and bite other resources—bigger blast radius.
Confidentiality (C:L)
Some sensitive info could get out, but not a total data dump.
Integrity (I:L)
Attackers could change some data, but it’s limited—not everything goes.
Availability (A:N)
Service keeps running; no real outage angle.
 2.8 2.7 [email protected]

Weakness enumeration for CVE-2021-4296

OS Trackers for CVE-2021-4296

vendor priority summary link
alpine — CVE-2021-4296: 1 source package rows (unicorn); 1 state rows across 1 repos (edge-community); fixed 0, open 1. https://security.alpinelinux.org/vuln/CVE-2021-4296

Affected software / configurations for CVE-2021-4296

Vendor Product Version Raw CPE
w3 unicorn < 2021-06-03 cpe:2.3:a:w3:unicorn:*:*:*:*:*:*:*:*

References for CVE-2021-4296

cvelogic Threat Intelligence