CVE-2025-13836 is a medium-severity vulnerability affecting the Python programming language. This vulnerability allows a malicious server to exploit the default behavior of the HTTP client when reading server responses. If no specific read amount is defined, the client defaults to using the Content-Length header. As a result, the client may read excessive amounts of data into memory, which can lead to out-of-memory (OOM) conditions or other denial-of-service (DoS) issues.
The CVSS score for this vulnerability is 6.3, indicating a medium severity level. It is crucial for organizations using Python in their applications to understand the potential risks associated with this vulnerability, as it may lead to service disruptions and affect overall system stability.
As of now, there is no known public exploit for CVE-2025-13836, and it is not classified as actively exploited. However, the absence of exploitation does not diminish the importance of addressing this vulnerability promptly. Organizations should prioritize remediation efforts to prevent potential impacts, especially in environments where Python is widely utilized.
Organizations should address this vulnerability in their priority patch cycle.
Vulnerability Details
The official description indicates that the vulnerability resides in the HTTP client of Python. When reading an HTTP response from a server without specifying a read amount, the default behavior utilizes the Content-Length header, which can be manipulated by a malicious server. This could lead to excessive data being read into memory.
The CVSS 4.0 vector string for CVE-2025-13836 is: CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:N/VI:N/VA:L/SC:N/SI:N/SA:L/E:X/CR:X/IR:X/AR:X. This indicates a network attack vector with low complexity and no privileges required for exploitation.
The vulnerability impacts all versions of Python prior to the vendor patch, specifically affecting versions like 3.14.0 and 3.15.0 alpha 1 and 2.
Technical Analysis
The root cause of CVE-2025-13836 stems from improper handling of the Content-Length header in HTTP responses. When a server response lacks a specified read amount, the HTTP client defaults to reading data based solely on the Content-Length. This misconfiguration can be exploited by a malicious server to craft responses that cause the client to read an excessive volume of data.
The attack vector for this vulnerability is classified as network-based, meaning an attacker could exploit it remotely over the internet. The attack complexity is low, and no privileges are required to exploit this vulnerability. Additionally, user interaction is not necessary, as the exploitation can occur without any actions from the user.
Regarding the impact, the confidentiality impact is none, while the integrity impact is also none. However, there is a low availability impact due to the potential for OOM scenarios that can disrupt the service.
Risk & Impact Analysis
Organizations using Python should assess their deployment to understand the potential risks associated with CVE-2025-13836. The ability of a malicious server to manipulate the Content-Length header and cause excessive memory consumption is a significant concern, particularly in environments where the application handles untrusted input from the network.
The blast radius for this vulnerability can vary based on the environment and the extent to which Python is relied upon. In cases where Python applications are integral to business operations, the risk of service disruption could have cascading effects on availability and user trust.
Given the CVSS score of 6.3, organizations should schedule remediation as part of their patch management strategy. While no active exploitation has been reported, the potential for future exploitation necessitates a proactive approach to security.
Exploitation Status
Signal | Status |
|---|---|
Known Exploit | No |
Public PoC | No |
Actively Exploited | No |
Ransomware Use | No |
Affected Versions
All versions of Python prior to the vendor patch are affected by this vulnerability. Specific versions known to be vulnerable include Python 3.14.0 and Python 3.15.0 alpha 1 and 2.
Mitigation & Remediation
Organizations should prioritize patching by upgrading to the latest version of Python that addresses CVE-2025-13836. If patches are unavailable, consider implementing workarounds such as setting a read amount when processing HTTP responses. Additionally, security configurations should be reviewed and hardened to limit exposure to potentially malicious servers.
For further information on secure coding practices, organizations can refer to the secure coding practices guide.
Detection Guidance
To detect potential exploitation of CVE-2025-13836, organizations should monitor logs for unusual HTTP response sizes and patterns that deviate from normal behavior. Additionally, behavioral anomalies in application performance could indicate attempts to exploit this vulnerability.
AppSecure Threat Intelligence Insight
CVE-2025-13836 highlights the importance of robust error handling and input validation in web applications. As organizations increasingly rely on third-party libraries, understanding the implications of vulnerabilities such as this one becomes crucial. Security teams should prioritize regular security assessments and implement continuous monitoring to detect potential weaknesses.
To further enhance security posture, organizations may consider engaging in penetration testing services that specifically evaluate the security of their applications.
Additionally, organizations should adopt a proactive approach to vulnerability management by establishing a vulnerability management program that focuses on timely patching and remediation strategies.
Finally, the significance of CVE-2025-13836 serves as a reminder for organizations to stay vigilant and informed about vulnerabilities in their software dependencies.
Disclaimer: This content was generated using AI. While we strive for accuracy, please verify critical information with official sources.
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