CVE-2026-21640 is a low-severity vulnerability discovered in the Revive Adserver by member Faraz Ahmed (PakCyberbot) of the HackerOne community. This vulnerability allows for a format string injection that can lead to a fatal PHP error when specific character combinations are utilized in the settings. As a result, the admin user console may become disabled, affecting the management capabilities of the application.
The vulnerability has a CVSS score of 2.7, indicating its low severity. While the risk of exploitation is minimal, it is crucial for organizations to be aware of this issue as it can lead to administrative disruptions. The vulnerability was published on January 20, 2026, and has been analyzed for potential impacts.
Organizations utilizing the affected version of Revive Adserver should prioritize the application of patches or updates. Even though the exploitability is rated low, timely remediation is essential to maintain operational integrity and security.
As of the last update, no public exploit has been confirmed, and the vulnerability is not included in the Known Exploited Vulnerabilities (KEV) catalog. Organizations should remain vigilant and monitor for any new developments regarding this vulnerability.
Urgency for defenders is moderate, and organizations should address this vulnerability in their regular patch cycles.
Vulnerability Details
The official CVE description states: "HackerOne community member Faraz Ahmed (PakCyberbot) has reported a format string injection in the Revive Adserver settings. When specific character combinations are used in a setting, the admin user console could be disabled due to a fatal PHP error."
The vulnerability is classified under CWE-134, which pertains to format string vulnerabilities. According to the CVSS 3.1 score, the attack vector is network-based, and it requires high privileges to exploit, with no user interaction necessary. This indicates that an attacker with administrative access could trigger the vulnerability without needing to involve other users.
The confidentiality impact is rated as none, while the integrity impact is low, and there is no impact on availability. This aligns with the overall low severity classification of the vulnerability.
Technical Analysis
The root cause of this vulnerability stems from improper handling of user input in the settings configuration of Revive Adserver. Specifically, certain character combinations can lead to format string injection, resulting in fatal errors that disable the admin user console.
This attack vector is classified as network, meaning it can be exploited remotely. The attack complexity is low, indicating that an attacker could exploit this vulnerability without significant effort, provided they have the necessary administrative privileges. User interaction is not required, further exacerbating the risk.
Consequently, the integrity impact is low, as the attacker does not gain unauthorized access to sensitive data but can disrupt the management functionalities of the application.
Risk & Impact Analysis
Risk to organizations includes potential administrative disruptions if the admin user console becomes disabled due to exploitation. While the severity is low, any disruption in management capabilities can lead to operational inefficiencies and hinder incident response capabilities.
The blast radius for this vulnerability is limited, as it primarily affects the administrative interface of Revive Adserver. However, organizations should assess their deployment to ensure adequate measures are in place to mitigate any potential impact.
Urgency assessment based on the CVSS score signifies that organizations should schedule remediation during their patch cycles. This vulnerability may not pose an immediate threat but should not be neglected.
Exploitation Status
Signal | Status |
|---|---|
Known Exploit | No |
Public PoC | No |
Actively Exploited | No |
Ransomware Use | No |
Affected Versions
The affected product is Revive Adserver, specifically versions 6.0.0 to 6.0.4. Organizations using these versions should prioritize updating to the latest patched version to mitigate the risk associated with this vulnerability.
Mitigation & Remediation
Organizations should apply the latest patches provided by Aquaplatform for Revive Adserver. If a patch is unavailable, consider implementing workarounds such as disabling specific settings that could trigger the vulnerability. Additionally, organizations should evaluate configuration hardening practices to minimize exposure.
Monitoring for unusual behavior in the application logs can help identify potential exploitation attempts. Regular security testing, including penetration testing, should be conducted to uncover vulnerabilities before they can be exploited.
Detection Guidance
Organizations should monitor logs for error messages that may indicate the exploitation of this vulnerability. Behavioral anomalies in user activity, especially in admin interfaces, should be scrutinized. Network signatures that highlight unusual requests to the Revive Adserver can also provide useful indicators.
AppSecure Threat Intelligence Insight
The long-term significance of CVE-2026-21640 lies in its representation of the potential risks associated with improper input handling in applications. As organizations increasingly rely on web-based platforms, understanding and mitigating such vulnerabilities becomes critical.
This vulnerability highlights the importance of rigorous security testing protocols, such as penetration testing methodology, to uncover potential weaknesses before they can be exploited.
Organizations should also consider integrating continuous security practices, such as continuous penetration testing, to maintain security resilience against evolving threats.
In conclusion, while the immediate risk posed by CVE-2026-21640 is low, organizations should take proactive measures to safeguard their systems against potential exploitation.
Disclaimer: This content was generated using AI. While we strive for accuracy, please verify critical information with official sources.
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