CVE-2021-35300Network attack vector

Content spoofing via malformed 404 rendering

Published Jun 28, 2021 · Updated Aug 4, 2024

Content spoofing in Zammad 1.0.x through 4.0.0 allows remote attackers to direct users to an attacker-controlled page via a crafted URL. The custom 404 page renders specially crafted request URLs incorrectly, but Zammad has not disclosed the faulty rendering operation or input transformation. Exploitation requires a user to request the crafted URL and act on the misleading page; no direct data access or code execution is reported.

CVSS severity4.3
Medium
EPSS probability0.89%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Content spoofing in Zammad 1.0.x through 4.0.0 allows remote attackers to direct users to an attacker-controlled page via a crafted URL. The custom 404 page renders specially crafted request URLs incorrectly, but Zammad has not disclosed the faulty rendering operation or input transformation. Exploitation requires a user to request the crafted URL and act on the misleading page; no direct data access or code execution is reported.

The record

CVE
CVE-2021-35300
Published
Jun 28, 2021
Updated
Aug 4, 2024
Vendor
Unknown vendor
Product
Unknown product
Classifications
CWE-1021, T1204.001
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Jun 28, 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 privilegesunauthenticated

What is affected?

Affected products and versions are unavailable in this record.

Published CVSS scores

4.3NIST NVDCVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:L/A:N
4.3NIST NVDAV:N/AC:M/Au:N/C:N/I:P/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-1021Improper Restriction of Rendered UI Layers or Frames
T1204.001Malicious Link

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

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Your stack

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