CVE-2021-4257Network attack vector

Stored cross-site scripting via unescaped display names

Published Dec 18, 2022 · Updated Aug 3, 2024

Stored cross-site scripting in Ctrlo Lenio's task handler allows remote authenticated users to inject script through saved display names. The task.tt template inserts organization, site, and check names directly into HTML, and the fix applies the Template Toolkit html filter to those fields. Exploitation requires permission to save a crafted name and a user to open the affected task page; the script then runs in that user's browser context.

CVSS severity6.1
Medium
EPSS probability0.39%
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

Stored cross-site scripting in Ctrlo Lenio's task handler allows remote authenticated users to inject script through saved display names. The task.tt template inserts organization, site, and check names directly into HTML, and the fix applies the Template Toolkit html filter to those fields. Exploitation requires permission to save a crafted name and a user to open the affected task page; the script then runs in that user's browser context.

The record

CVE
CVE-2021-4257
Published
Dec 18, 2022
Updated
Aug 3, 2024
Vendor
Ctrlo
Product
Lenio
Classifications
CWE-79, CWE-707, T1203
Attack vector
network
Privileges
authenticated

Timeline

How it unfolded

  1. Dec 18, 2022CVE 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=n/a

What conditions does exploitation require?

Attack vectornetwork
Required privilegesauthenticated

What is affected?

Ctrlo · Lenioversion=n/a

Published CVSS scores

3.5VulDBCVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:U/C:N/I:L/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
Privilegesauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-79Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting')
CWE-707Improper Neutralization
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