CVE-2025-29419 in CTFd
Summary
by MITRE • 08/26/2026
CTFd v3.7.6 was discovered to be vulnerable to a man-in-the-middle attack.
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Analysis
by VulDB Data Team • 08/26/2026
The vulnerability identified in CTFd version 3.7.6 represents a critical security flaw that undermines the integrity of communications between clients and the server, specifically facilitating man-in-the-middle attacks. As an open-source Capture The Flag platform widely used for cybersecurity competitions, education, and training exercises, maintaining the confidentiality and authenticity of data transmitted during these events is paramount. When this vulnerability is present, attackers positioned within the network path can intercept, read, or potentially alter the traffic exchanged between participants and the CTFd server without detection. This compromise erodes trust in the platform's ability to securely manage sensitive competition data, including user credentials, challenge submissions, and scoring information.
From a technical perspective, this vulnerability typically stems from improper implementation of transport layer security protocols or missing enforcement mechanisms that ensure encrypted connections are used exclusively. In many web applications, if HTTPS is not strictly enforced via secure headers such as Strict-Transport-Security (HSTS), or if the application allows fallback to unencrypted HTTP under certain conditions, it creates an opportunity for network-level attackers to perform protocol downgrade attacks. By intercepting initial requests that may be sent over plain text HTTP, an adversary can inject malicious scripts, modify challenge content in transit, or capture session cookies and authentication tokens. This is particularly dangerous in CTF environments where participants often use shared networks or public Wi-Fi, increasing the attack surface for such interception attempts.
The operational impact of this vulnerability extends beyond simple data leakage. In a competitive setting, an attacker could manipulate the outcome by altering challenge flags submitted by players before they reach the server, effectively changing scores and rankings without authorization. Furthermore, if session hijacking occurs through cookie theft via unencrypted channels, attackers can impersonate legitimate users to access administrative functions or other participants' private data. This not only compromises individual privacy but also undermines the fairness of the competition itself. For organizations using CTFd for internal security training, this flaw could expose proprietary methodologies and sensitive infrastructure details that are part of the exercise design, leading to broader organizational risk exposure beyond the immediate event scope.
To mitigate these risks, it is essential to enforce strict HTTPS usage across all endpoints within the CTFd deployment. Administrators should configure their reverse proxies or web servers to redirect all HTTP traffic to HTTPS and implement the Strict-Transport-Security header with a long max-age value to prevent protocol downgrade attacks. Additionally, ensuring that TLS configurations adhere to modern security standards by disabling outdated protocols like SSLv3 and TLS 1.0/1.1 is crucial. Regular updates to CTFd are necessary as newer versions likely address these cryptographic enforcement gaps. Security teams should also monitor network traffic for anomalies indicative of MITM attempts and consider implementing certificate pinning in client-side applications if applicable, although this is less common in standard web-based interfaces.
This vulnerability aligns with CWE-319, which classifies the use of a cleartext protocol susceptible to man-in-the-middle attacks as a significant weakness. It also maps closely to MITRE ATT&CK technique T1048, specifically subtechnique T1048.002 for Exfiltration Over Alternative Protocol, and potentially T1557 if the attacker is performing adversary-in-the-middle to capture credentials or session tokens during active logon processes. Understanding these mappings helps security professionals contextualize the threat within broader attack frameworks and prioritize remediation efforts accordingly. By addressing this flaw, organizations can restore confidence in the secure operation of their CTFd instances and protect both participant data and competitive integrity from network-based interception threats.