CVE-2020-10821Public exploitNetwork attack vector

Authenticated script execution via unsanitized theme parameter

Published Mar 22, 2020 · Updated Aug 4, 2024

Reflected XSS in Nagios XI 5.6.11 allows remote authenticated users to execute script in another user’s browser via a crafted theme value. The account/main.php page processes the theme query parameter without sufficient neutralization, causing attacker-supplied markup to execute when a victim follows the crafted request. An authenticated account and victim interaction are required; exploitation can read or modify browser-accessible data in the victim’s session.

CVSS severity4.8
Medium
EPSS probability71.13%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Reflected XSS in Nagios XI 5.6.11 allows remote authenticated users to execute script in another user’s browser via a crafted theme value. The account/main.php page processes the theme query parameter without sufficient neutralization, causing attacker-supplied markup to execute when a victim follows the crafted request. An authenticated account and victim interaction are required; exploitation can read or modify browser-accessible data in the victim’s session.

The record

CVE
CVE-2020-10821
Published
Mar 22, 2020
Updated
Aug 4, 2024
Vendor
Unknown vendor
Product
Unknown product
Classifications
CWE-79, T1203
Attack vector
network
Privileges
authenticated

Timeline

How it unfolded

  1. Mar 22, 2020CVE publishedPublication date reported by the CVE source.
  2. Aug 4, 2024Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

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Is a vulnerable build present?

Affected buildAffected product and version details are unavailable.

What conditions does exploitation require?

Attack vectornetwork
Required privilegesauthenticated

What is affected?

Affected products and versions are unavailable in this record.

Published CVSS scores

3.5NIST NVDAV:N/AC:M/Au:S/C:N/I:P/A:N
4.8NIST NVDCVSS:3.1/AV:N/AC:L/PR:H/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 exploitPublished

Weakness, pattern, technique

CWE-79Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting')
T1203Exploitation for Client Execution

Public exploit references

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

Technologies

Your stack

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Your stack

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