What is the CVSS score of CVE-2026-21663?

CVE-2026-21663 has a CVSS 3.0 base score of 6.1 (Medium). CVSS vector: CVSS:3.0/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N. EPSS exploitation probability: 0.0%.

Which versions of PHP are affected by CVE-2026-21663?

CVE-2026-21663 presents moderate security risk, a cross-site scripting vulnerability rated CVSS 6.1. Attackers could inject scripts to steal sessions or perform actions as authenticated users.

How to fix or mitigate CVE-2026-21663?

Within 30 days: Identify affected systems and apply vendor patches as part of regular patch cycle. Verify Content-Security-Policy and output encoding.

PHP CVE-2026-21663

MEDIUM

Cross-site Scripting (XSS) (CWE-79)

2026-01-20 support@hackerone.com

PHP XSS Revive Adserver

6.1

CVSS 3.0 · NVD

Severity by source

NVD PRIMARY

6.1 MEDIUM

AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N

Primary rating from NVD · only source for this CVE.

CVSS VectorNVD

CVSS:3.0/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N

Attack Vector

Network

Attack Complexity

Low

Privileges Required

None

User Interaction

Required

Scope

Changed

Confidentiality

Low

Integrity

Low

Availability

None

Lifecycle Timeline

Analysis Generated

Mar 12, 2026 - 21:54 vuln.today

CVE Published

Jan 20, 2026 - 21:16 nvd

MEDIUM 6.1

DescriptionCVE.org

HackerOne community member Patrick Lang (7yr) has reported a reflected XSS vulnerability in the banner-acl.php script of Revive Adserver. An attacker can craft a specific URL that includes an HTML payload in a parameter. If a logged in administrator visits the URL, the HTML is sent to the browser and malicious scripts would be executed.

AnalysisAI

Revive Adserver's banner-acl.php script contains a reflected cross-site scripting vulnerability that allows attackers to execute arbitrary scripts in the browsers of authenticated administrators through a crafted URL. An attacker can inject malicious HTML payloads into vulnerable parameters, which execute when an admin visits the malicious link, potentially compromising administrative sessions and server configuration. No patch is currently available for this vulnerability.

Technical ContextAI

Classified as CWE-79 (Cross-site Scripting (XSS)). Affects Revive Adserver. HackerOne community member Patrick Lang (7yr) has reported a reflected XSS vulnerability in the banner-acl.php script of Revive Adserver. An attacker can craft a specific URL that includes an HTML payload in a parameter. If a logged in administrator visits the URL, the HTML is sent to the browser and malicious scripts would be executed.

RemediationAI

Monitor vendor advisories for a patch. Implement output encoding and Content Security Policy headers. Restrict network access to the affected service where possible.