CVE-2026-21664VulnerabilityPublished 20 Jan 2026

CVE-2026-21664: Revive Adserver · Cross-site Scripting

Affects Revive AdserverSource CVE Database V5

Not known to be exploited · CVSS 6.1 Medium.

Data as of 26 Oct 2026, 06:26 UTC

CVSS 3.0 base score

6.1Medium

How severe the flaw is on the 0–10 CVSS scale.

EPSS: 0.2% chance of exploitation in 30 days – higher than 9% of CVEsExploit Prediction Scoring System: the likelihood attackers will use this flaw soon.

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

Bold values are the worst case: easiest to exploit or largest impact.

Attack Vector: Network: The vulnerable component is bound to the network stack and the set of possible attackers extends beyond the other options listed, up to and including the entire Internet. Such a vulnerability is often termed 'remotely exploitable' and can be thought of as an attack being exploitable at the protocol level one or more network hops away (e.g., across one or more routers).
Attack Complexity: Low: Specialized access conditions or extenuating circumstances do not exist. An attacker can expect repeatable success against the vulnerable component.
Privileges Required: None: The attacker is unauthorized prior to attack, and therefore does not require any access to settings or files to carry out an attack.
User Interaction: Required: Successful exploitation of this vulnerability requires a user to take some action before the vulnerability can be exploited.
Scope: Changed: An exploited vulnerability can affect resources beyond the security scope managed by the security authority of the vulnerable component. In this case, the vulnerable component and the impacted component are different and managed by different security authorities.
Confidentiality: Low: There is some loss of confidentiality. Access to some restricted information is obtained, but the attacker does not have control over what information is obtained, or the amount or kind of loss is limited. The information disclosure does not cause a direct, serious loss to the impacted component.
Integrity: Low: Modification of data is possible, but the attacker does not have control over the consequence of a modification, or the amount of modification is limited. The data modification does not have a direct, serious impact on the impacted component.
Availability: None: There is no impact to availability within the impacted component.

Definitions: FIRST CVSS v3.1 specification.

Exploitation evidence

Disclosed: evidence found.
CVE published 20 Jan 2026
Detectable: no evidence on record.
No public nuclei template indexed
Weaponised: no evidence on record.
No public exploit code indexed in Metasploit or Exploit-DB
Exploited in the wildExploited: no evidence on record.
Not in CISA KEV and no source reports exploitation
Observed by OffSeq MirageSeen by Mirage: no evidence on record.
No attack traffic recorded by OffSeq Mirage sensors

A missing step is not evidence of safety. Sources: cve.org (opens in a new tab), the Metasploit, Exploit-DB and nuclei-templates index as of 2026-10-26.

Disclosed: The CVE record is public on cve.org. Its publication is t = 0.
Detectable: A public nuclei template can find exposed instances, for defenders and attackers alike.
Weaponised: Public exploit code exists in Metasploit or Exploit-DB, or CISA SSVC reports a public proof of concept.
Exploited in the wild: CISA KEV lists it, CISA SSVC rates exploitation active, or a source reports attacks.
Observed by OffSeq Mirage: OffSeq Mirage honeypot sensors recorded attack traffic for this CVE, or found exposed hosts without attack traffic.

Moments are spaced evenly, not to scale; a dashed line marks a gap of six months or more. Deltas count from t = 0. Sources that give only a date (CISA KEV, Exploit-DB, or a time of exactly 00:00Z) read “same day” rather than hours. Metasploit modules carry the flaw’s disclosure date, not their release date, and nuclei templates carry no date, so both appear above but not on the timeline.

What to do

Affected software

Product	Affected	Fixed in
ReviveRevive Adserver	Affected >=6 <=6.0.4	Fixed in–

AI-suggested

European organizations should immediately review their use of Revive Adserver version 6 and monitor for any vendor patches or updates addressing CVE-2026-21664. In the absence of an official patch, implement input validation and output encoding on the afr.php script parameters to neutralize malicious payloads. Deploy Content Security Policy (CSP) headers to restrict the execution of unauthorized scripts in the browser context. Educate administrators on the risks of clicking unsolicited or suspicious URLs, especially those purporting to relate to adserver management. Employ multi-factor authentication (MFA) for administrator accounts to reduce the impact of session hijacking. Monitor web server logs for unusual URL access patterns that may indicate exploitation attempts. Consider isolating the adserver administration interface behind VPN or IP whitelisting to limit exposure. Regularly back up configuration and campaign data to enable recovery in case of compromise.

Description

CVE-2026-21664 is a reflected Cross-Site Scripting (XSS) vulnerability in the afr.php delivery script of Revive Adserver version 6. An attacker can craft a malicious URL containing an HTML payload that, when visited by a logged-in administrator, executes arbitrary scripts in the administrator's browser. This vulnerability requires user interaction and affects confidentiality and integrity but not availability. No known exploits are currently in the wild. The vulnerability has a CVSS 3.0 score of 6.1, indicating medium severity. European organizations using Revive Adserver 6 should prioritize patching or mitigating this issue to prevent potential administrative account compromise or session hijacking. Countries with significant digital advertising sectors and high usage of Revive Adserver are at greater risk.

Impact

For European organizations, this vulnerability can lead to unauthorized access to administrative functions within Revive Adserver, potentially allowing attackers to manipulate ad campaigns, steal sensitive data, or pivot to other internal systems. Given that Revive Adserver is widely used by digital marketing agencies, media companies, and publishers across Europe to manage online advertising, exploitation could disrupt advertising operations and damage brand reputation. The confidentiality of administrator credentials and session tokens is at risk, which could lead to broader compromise if attackers leverage stolen credentials elsewhere. While availability is not directly impacted, the integrity of advertising content and reporting data could be compromised, affecting business decisions and revenue. Organizations with strict data protection regulations, such as GDPR, must consider the implications of such breaches on personal data processed via the platform. The requirement for administrator interaction reduces the likelihood of mass exploitation but targeted spear-phishing or social engineering attacks could be effective.

CWE-79Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting') (opens in a new tab)
Base weaknessLikelihood of exploit: HighCWE Top 25 (2025): #1OWASP Top 10 A05:2025: Injection (opens in a new tab)
The product does not neutralize or incorrectly neutralizes user-controllable input before it is placed in output that is used as a web page that is served to other users.
Architecture and Design · Libraries or Frameworks
Use a vetted library or framework that does not allow this weakness to occur or provides constructs that make this weakness easier to avoid.
Implementation · Architecture and Design
Understand the context in which your data will be used and the encoding that will be expected. This is especially important when transmitting data between different components, or when generating outputs that can contain multiple encodings at the same time, such as web pages or multi-part mail messages.
Architecture and Design · Implementation · Attack Surface Reduction
Understand all the potential areas where untrusted inputs can enter your software: parameters or arguments, cookies, anything read from the network, environment variables, reverse DNS lookups, query results, request headers, URL components, e-mail, files, filenames, databases, and any external systems that provide…
OWASP Cheat Sheets
Cross Site Scripting Prevention (opens in a new tab)
DOM based XSS Prevention (opens in a new tab)
Injection Prevention (opens in a new tab)
Abuse Case (opens in a new tab)
Deserialization (opens in a new tab)
OWASP ASVS 4.0.3
V5.3.3 (opens in a new tab)
V1.5.1 (opens in a new tab)
Attack patterns
XSS Using MIME Type Mismatch (opens in a new tab)
DOM-Based XSS (opens in a new tab)
Reflected XSS (opens in a new tab)
Stored XSS (opens in a new tab)
Cross-Site Scripting (XSS) (opens in a new tab)
From MITRE CWE, MITRE CAPEC and OWASP (Top 10, OpenCRE).

References

hackerone.com/reports/3468169 (opens in a new tab)

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Exploitation evidence

What to do

Affected software

Description

AI analysisMachine-generated, updated 28 Jan 2026, 20:22 UTC

WeaknessesCWE-79

Technical details

References

Community reviews

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