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Revive Adserver CVE-2026-50745

| EUVDEUVD-2026-39605 MEDIUM
Cross-site Scripting (XSS) (CWE-79)
2026-06-26 hackerone GHSA-8xrw-qpv5-m4qm
6.1
CVSS 3.1 · NVD
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Attack ChainAIDerived

Hypothetical attack flow derived from CVE metadata – not a confirmed exploit chain

  1. Access
    Identify stats-video.php endpoint
  2. Delivery
    Craft URL with unsanitized XSS payload
  3. Exploit
    Social engineer victim into clicking link
  4. Execution
    Victim browser requests malicious URL
  5. Persist
    Smarty url() reflects payload unescaped
  6. Impact
    JavaScript executes in victim browser under adserver origin

Vulnerability Assessment

Weakness
CWE
OWASP Top 10:2025
A05:2025 - Injection
ASVS 5.0
V1 - Encoding and Sanitization Output encoding, context-aware escaping
MITRE ATT&CK

2 techniques across 2 tactics: Initial Access, Execution

The technique list with ATT&CK links and the kill-chain view is part of the Basic plan and up.

Exploitation Conditions

Exploitation requires the victim to interact with a specially crafted URL pointing to the stats-video.php script (UI:R per CVSS vector). The attacker does not need any authentication credentials (PR:N). The description notes that URL construction for this script did not follow best practices, implying specific URL parameter patterns are needed - the exact parameter name is not disclosed in available data. Exploitation is limited by: (1) victim must actively follow or be redirected to the crafted URL; (2) the vulnerable script must be publicly accessible (i.e., the adserver's stats-video.php endpoint is reachable from the attacker's network); (3) AC:H in the original CVSS vector suggests some URL crafting complexity, possibly related to how the script expects URL structure. There is no indication of a non-default configuration requirement - the vulnerability appears present in the standard deployment of the stats-video.php endpoint.

Impact

The NVD-assigned CVSS 3.0 score is 4.7 (Medium) with vector AV:N/AC:H/PR:N/UI:R/S:C/C:L/I:L/A:N. The Scope:Changed designation reflects that exploitation crosses from the web application into the victim's browser security context, which is correct for reflected XSS. The AC:H rating in the original vector likely captures the specific URL construction constraints described, though this analyst assesses AC:L as more representative once the vulnerable parameter is identified (see assessed vector). No EPSS data was provided in the input; no KEV listing exists; no confirmed public exploit code has been identified. Taken together, the real-world risk is moderate: while reflected XSS typically requires social engineering to deliver the crafted link (UI:R), the lack of any authentication requirement (PR:N) means any internet user could be targeted. The primary limiting factor is victim interaction, not attacker capability. This is a genuine security issue but not an emergency patch priority absent active exploitation evidence.

Exploit ScenarioDerived

An attacker identifies the vulnerable parameter in the stats-video.php URL and crafts a link embedding a JavaScript payload (e.g., a cookie-stealing script) that passes through the Smarty url helper without encoding. The attacker then delivers this URL to a victim - typically via email, chat, or a compromised third-party page - and when the victim's browser requests the URL, the adserver reflects the payload back in the response, executing it in the victim's browser session under the adserver's origin. No public exploit code has been identified at time of analysis, but reflected XSS of this type is straightforward to exploit manually.

This Month Plan within 30 days. Why: MEDIUM severity (CVSS 4.0-6.9).
No patch listed yet 0.1% exploitation probability (EPSS)

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AnalysisAIv1 – Jun 26, 2026

Reflected cross-site scripting in Revive Adserver's stats-video.php script allows remote attackers to inject arbitrary JavaScript into victim browsers by delivering a crafted URL. The Smarty template engine's custom url helper function emits attacker-controlled values without HTML encoding or sanitization, and the URL construction pattern for this endpoint exposes user input directly in rendered output. No active exploitation has been confirmed (not in CISA KEV), but the vulnerability is reachable without authentication and requires only victim interaction with a malicious link.

RemediationAI

The primary fix is to apply output encoding to all values emitted by the Smarty url custom helper function in stats-video.php, and to audit other Smarty helper outputs for the same pattern. Refer to the vendor disclosure at https://hackerone.com/reports/3793243 for the precise patch or commit. No specific patched release version was confirmed in the available input data - monitor the Revive Adserver project for an official release addressing this report. As a compensating control prior to patching, operators can implement a Content Security Policy (CSP) header that restricts inline script execution (script-src 'self'), which will block most reflected XSS payloads from executing even if the parameter remains unsanitized; note that overly broad CSP policies may break legitimate adserver functionality and require testing. Web application firewall rules targeting XSS signatures on the stats-video.php endpoint can also reduce exposure, though WAF bypass is always possible for a determined attacker.

Affected VersionsENISA

Adserver 0 ≤6.0.7

Affected Packages

euvd adserver no fix

Source: OSV (Open Source Vulnerabilities)

Affects your stack

Affects 1 package in euvd

Checking this CVE against your own stacks and servers is part of the Basic plan and up.

Technical ContextAI · show details

Revive Adserver is a PHP-based open-source ad serving platform that uses the Smarty templating engine. The affected component is stats-video.php, which relies on a custom Smarty helper function named url to construct output URLs. CWE-79 (Improper Neutralization of Input During Web Page Generation / XSS) identifies the root cause: user-supplied values passed through this helper are reflected directly into the HTTP response without context-aware HTML encoding. CPE cpe:2.3:a:revive:adserver:*:*:*:*:*:*:*:* covers all versions of the adserver product, indicating no version range has been explicitly bounded in NVD data. The vulnerability class is classic reflected (Type 1) XSS - no persistence on the server is required; the payload travels in the request and is echoed back in the response.

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  • Exploit and PoC references, threat intelligence from 22 sources

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Severity by source

Vendor (hackerone) PRIMARY MEDIUM
NVD 6.1 MEDIUM
AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N
vuln.today AI 6.1 MEDIUM

Reflected XSS via crafted URL requires no auth and is low complexity once the parameter is known; scope changes to victim browser; no availability impact.

3.1 AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N
4.0 AV:N/AC:L/AT:N/PR:N/UI:A/VC:N/VI:N/VA:N/SC:L/SI:L/SA:N

Primary rating from Vendor (hackerone).

CVSS VectorNVD

Attack Vector
Network
Attack Complexity
Low
Privileges Required
None
User Interaction
Required
Scope
Changed
Confidentiality
Low
Integrity
Low
Availability
None

Lifecycle Timeline

1
CVSS changed
Jun 29, 2026 - 20:22 NVD
4.7 (MEDIUM) 6.1 (MEDIUM)

DescriptionNVD

A missing sanitisation vulnerability exists with user input in the stats-video.php script. The way URLs to this script were constructed did not follow best practices, and the output of the Smarty custom helper function url was neither properly encoded nor sanitised, allowing user‑supplied input to be reflected without escaping.

Threat Intelligence Overview

EPSS Score
0.1%
Top 97% exploitable
Prevalence
Low
open-source adserver with limited enterprise adoption
Social Media
1
Sightings
Data Quality
5 sources
Confidence: Medium

How this decision was reached

The engine reads each signal below and applies a fixed list of rules from top to bottom. The first rule that matches sets the recommended action – like a statement, every line is shown.

SignalValue
Severity MEDIUM
CISA KEV No
Public POC No
EPSS 0.1%
Patch available No
Active threat No
Deciding rule
MEDIUM severity (CVSS 4.0-6.9)
What every action level means
Emergency Immediate action required. Criteria: CRITICAL + in CISA KEV (actively exploited) without patch, OR CRITICAL + EPSS > 30% without patch, OR CRITICAL + active threat signals without patch.
Act Now Prioritize within 24-48h. Criteria: in KEV with patch available, OR CRITICAL + public POC, OR HIGH + EPSS > 10%, OR CRITICAL + active threat, OR any CRITICAL severity.
This Week Schedule remediation this week. Criteria: HIGH severity (CVSS 7.0-8.9). Patch within normal change window.
This Month Plan within 30 days. Criteria: MEDIUM severity (CVSS 4.0-6.9), lower exploitation probability. Include in regular patch cycle.
Monitor Track and reassess. Criteria: LOW severity (CVSS 0.1-3.9), minimal exploitation risk. No immediate action needed.

SSVC AssessmentENISA

SSVC Decision· derived
Scheduled
Exploitation
None
System Exposure· derived
Open
Automatable
No
Human Impact· derived
Medium
Technical Impact
Partial

Priority Score

30
Low Medium High Critical
KEV: 0
EPSS: 0
CVSS: +30
PoC: 0
Weaponized: 0
Threat intel: 0
Gov advisory: 0

Attack Technique

Cross-Site Scripting occurs when an application accepts untrusted data and sends it to a web browser without proper validation or encoding.

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