CVE-2021-22872Public exploitNetwork attack vector

Legacy-browser script execution via unescaped destination slash

Published Jan 21, 2021 · Updated Aug 3, 2024

Reflected XSS in Revive Adserver 5.0.5 and earlier allows remote attackers to execute script via public afr.php requests in legacy browsers. The afr.php delivery code embeds the destination parameter in JavaScript after double escaping that omits forward slashes, allowing closing and opening script tags. A victim must follow a crafted link in a browser that does not automatically URL-encode parameters; JavaScript cannot read the session cookie.

CVSS severity4.3
Medium
EPSS probability3.45%
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 Revive Adserver 5.0.5 and earlier allows remote attackers to execute script via public afr.php requests in legacy browsers. The afr.php delivery code embeds the destination parameter in JavaScript after double escaping that omits forward slashes, allowing closing and opening script tags. A victim must follow a crafted link in a browser that does not automatically URL-encode parameters; JavaScript cannot read the session cookie.

The record

CVE
CVE-2021-22872
Published
Jan 21, 2021
Updated
Aug 3, 2024
Vendor
Revive Adserver Project
Product
Revive Adserver
Classifications
CWE-79, T1189
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Jan 21, 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?

Compare these published version ranges with your installed build and any vendor patches.

  1. Affected versionversion=Fixed in 5.1.0

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

Revive Adserver Project · Revive Adserverversion=Fixed in 5.1.0

Published CVSS scores

6.1NIST National Vulnerability DatabaseCVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N
4.3Revive Adserver Project TeamCVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:L/I:N/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 exploitPublished

Weakness, pattern, technique

CWE-79Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting')
T1189Drive-by Compromise

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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