CVE-2021-35478Public exploitNetwork attack vector

Reflected XSS via unencoded audit-log filters

Published Jul 27, 2021 · Updated Aug 4, 2024

Reflected XSS in Nagios Log Server before 2.1.9 allows remote authenticated users to run scripts in another user's browser. The audit-log and alert-history dropdown reflects the time, start, end, type, and search filter parameters into HTML without correct encoding. A victim must open a crafted link or third-party page, enabling script execution in the Nagios origin that can steal cookies or redirect the browser.

CVSS severity5.4
Medium
EPSS probability76.62%
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 Log Server before 2.1.9 allows remote authenticated users to run scripts in another user's browser. The audit-log and alert-history dropdown reflects the time, start, end, type, and search filter parameters into HTML without correct encoding. A victim must open a crafted link or third-party page, enabling script execution in the Nagios origin that can steal cookies or redirect the browser.

The record

CVE
CVE-2021-35478
Published
Jul 27, 2021
Updated
Aug 4, 2024
Vendor
Unknown vendor
Product
Unknown product
Classifications
CWE-79, T1204.001
Attack vector
network
Privileges
authenticated

Timeline

How it unfolded

  1. Jul 27, 2021CVE 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

4.6NCC GroupCVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:U/C:L/I:L/A:N
3.5NIST NVDAV:N/AC:M/Au:S/C:N/I:P/A:N
5.4NIST NVDCVSS:3.1/AV:N/AC:L/PR:L/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')
T1204.001Malicious Link

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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