CVE-2021-28963Network attack vector

Phishing via query-overridden template placeholders

Published Mar 22, 2021 · Updated Aug 3, 2024

Content injection in Shibboleth Service Provider before 3.2.1 allows remote attackers to alter error and status pages via crafted URLs. Its primitive template engine permits query parameters to override internally supplied placeholders, while encoding blocks script injection. Unauthenticated URL manipulation can replace displayed email addresses, logos, style sheets, and support links, making phishing content appear trustworthy without executing scripts.

CVSS severity5.3
Medium
EPSS probability1.31%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Content injection in Shibboleth Service Provider before 3.2.1 allows remote attackers to alter error and status pages via crafted URLs. Its primitive template engine permits query parameters to override internally supplied placeholders, while encoding blocks script injection. Unauthenticated URL manipulation can replace displayed email addresses, logos, style sheets, and support links, making phishing content appear trustworthy without executing scripts.

The record

CVE
CVE-2021-28963
Published
Mar 22, 2021
Updated
Aug 3, 2024
Vendor
Unknown vendor
Product
Unknown product
Classifications
CWE-74, T1566
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Mar 22, 2021CVE 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

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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

5.3NIST National Vulnerability DatabaseCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:N
5.0NIST National Vulnerability DatabaseAV:N/AC:L/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-74Improper Neutralization of Special Elements in Output Used by a Downstream Component ('Injection')
T1566Phishing

Public exploit references

No public exploit references are available in this record.

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Technologies

Your stack

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Your stack

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