CVE-2025-55753 represents a high-severity vulnerability that allows an integer overflow in the Apache HTTP Server, specifically during failed ACME certificate renewals. This vulnerability is particularly critical as it can cause the backoff timer to reset to zero after a predefined number of failures, leading to continuous attempts to renew the certificate without any delays. This issue affects versions from 2.4.30 to before 2.4.66, making it essential for users to upgrade to version 2.4.66 or later to mitigate this risk.
The severity level of this vulnerability is classified as high, with a CVSS score of 7.5. This rating indicates that the potential impact on organizations can be significant, particularly for those relying on the Apache HTTP Server for secure communications. The vulnerability's exploitability is high, meaning attackers may leverage this flaw to disrupt services or bypass security measures.
Risk to organizations includes unauthorized access to sensitive data due to certificate renewal failures. As the vulnerability allows for repeated attempts without delays, it may lead to denial of service scenarios or expose the server to additional attacks during the renewal process. Given the potential impact, organizations should prioritize patching immediately.
Currently, there is no known public exploit for this vulnerability, and it has not been classified as actively exploited in the wild. However, the high exploitability score indicates that organizations should remain vigilant in applying the recommended updates and monitoring their systems.
Vulnerability Details
According to the official CVE description, this vulnerability allows an integer overflow during the ACME certificate renewal process. The issue arises when there are multiple failed attempts to renew the certificate, causing the backoff timer to reach zero, leading to an uncontrolled number of renewal attempts.
The affected product is the Apache HTTP Server, specifically versions prior to 2.4.66. The vulnerability has been assigned a CVSS score of 7.5, indicating high severity. The vulnerability was published on December 5, 2025, and affects systems that are configured with default settings.
Technical Analysis
The root cause of CVE-2025-55753 is an integer overflow in the ACME certificate renewal logic, which is primarily network-exploitable. The attack complexity is low, meaning that an attacker does not require elevated privileges to exploit this vulnerability. Furthermore, no user interaction is necessary for exploitation. The impact on confidentiality is high, as successful exploitation could lead to information disclosure or unauthorized access.
Risk & Impact Analysis
Real-world deployment risk associated with this vulnerability is significant, particularly for organizations using Apache HTTP Server for critical applications. Organizations that rely on digital certificates for secure communications could face severe consequences in the event of successful exploitation. The blast radius of this vulnerability can affect any service utilizing the affected versions of the server, potentially leading to widespread disruption.
Organizations should assess their risk based on the CVSS score and prioritize remediation in their patch management cycle. The urgency is high due to the potential for data exposure and service disruption.
Exploitation Status
Signal | Status |
|---|---|
Known Exploit | No |
Public PoC | No |
Actively Exploited | No |
Ransomware Use | No |
Affected Versions
The vulnerability affects Apache HTTP Server versions from 2.4.30 to before 2.4.66. Organizations should upgrade to version 2.4.66 or later to mitigate this risk.
Mitigation & Remediation
To remediate this vulnerability, organizations should apply the latest patches provided by Apache. Users are recommended to upgrade to version 2.4.66, which fixes the issue. If immediate patching is not possible, temporary workarounds may include monitoring the certificate renewal process more closely.
Organizations should validate remediation through penetration testing to ensure that the vulnerability has been effectively mitigated.
Detection Guidance
Organizations should monitor logs for unusual activities related to certificate renewals. Detection mechanisms should focus on identifying rapid succession of renewal attempts that may indicate exploitation of this vulnerability. Behavioral anomalies during the renewal process should also be logged for further investigation.
AppSecure Threat Intelligence Insight
The long-term significance of CVE-2025-55753 lies in its potential to disrupt secure communications for organizations that rely on the Apache HTTP Server. This vulnerability represents a critical flaw in the certificate renewal process, emphasizing the importance of robust validation mechanisms in security protocols. Security teams should prioritize regular assessments and updates to their systems to prevent similar vulnerabilities.
To further enhance security posture, organizations may consider implementing continuous security testing practices. Engaging in continuous penetration testing can help identify and remediate vulnerabilities proactively.
Furthermore, organizations should consider integrating application security assessments into their development lifecycle to ensure that similar weaknesses are identified early.
Lastly, organizations should stay informed of emerging threats and trends in security vulnerabilities to better prepare for future challenges. Regularly reviewing resources on vulnerability management programs can provide valuable insights into best practices for maintaining a secure infrastructure.
Disclaimer: This content was generated using AI. While we strive for accuracy, please verify critical information with official sources.
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