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February 6, 2025
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How to Fix CVE-2025-0665: A Critical Resource Management Vulnerability in libcurl?
libcurl, a widely used library for transferring data with URLs, has recently been found to contain a critical vulnerability that could lead to resource management issues and system instability. This flaw, identified as CVE-2025-0665, involves a double close of the same eventfd file descriptor, potentially causing applications to crash or become unresponsive. This article provides security professionals with a comprehensive guide on understanding, detecting, and mitigating this vulnerability to protect their systems and applications. We will delve into the technical details, affected versions, and practical steps to address this issue effectively.
A Short Introduction to libcurl
libcurl is a free and open-source client-side URL transfer library supporting various protocols, including HTTP, HTTPS, FTP, and many others. It is designed to be highly portable and is used in a wide range of applications across different platforms and operating systems. Security professionals in DevSecOps, application security, and vulnerability management rely on libcurl for its robust features and widespread integration in their products and services. Understanding libcurl and its vulnerabilities is crucial for maintaining a secure software ecosystem.
Summary of CVE-2025-0665
CVE ID: CVE-2025-0665
Description: libcurl would wrongly close the same eventfd file descriptor twice when taking down a connection channel after having completed a threaded name resolve.
CVSS Score: 9.8 (Critical)
CVSS Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
This vulnerability arises from a flaw in libcurl's handling of eventfd file descriptors during the shutdown of connection channels after a threaded name resolution. Specifically, the same eventfd file descriptor is inadvertently closed twice. This double close can lead to unpredictable behavior and potentially severe consequences, making it a critical issue that demands immediate attention. The flaw is triggered when libcurl is built with the threaded resolver and eventfd support, typically on 64-bit architectures. An #ifdef mistake resulted in the superfluous close() call remaining active, leading to the double free.
Impact of CVE-2025-0665
The impact of CVE-2025-0665 can be significant. Closing the same file descriptor twice may result in resource management issues or system instability. This could lead to application crashes, making services unavailable or even lead to denial-of-service conditions. In certain scenarios, it could also lead to information leakage or the potential exploitation of system resources. Although there is no evidence of active exploitation, the high CVSS score indicates the potential for severe impact, and security teams should prioritize remediation. The ability to cause crashes or potentially leak information makes this a critical vulnerability that needs to be addressed promptly to prevent potential attacks and maintain system integrity.
Products Affected by CVE-2025-0665
The following table summarizes the versions of curl affected by CVE-2025-0665:
|
Product
|
Version(s) Affected
|
Version(s) Not Affected
|
|---|---|---|
|
curl
|
8.11.1
|
< 8.11.1, >= 8.12.0
|
It is important to note that libcurl is used by numerous applications, often without explicit advertisement. Therefore, security professionals should assess all applications using libcurl to determine potential vulnerability. The vulnerability is introduced by a specific commit (92124838c6b7e09e3f35f) and fixed by another commit (ff5091aa9f73802e894b1cbdf).
How to Check Your Product is Vulnerable?
Identifying whether your systems are vulnerable to CVE-2025-0665 involves several steps:
Check libcurl Version: Determine the version of libcurl used in your applications or systems. You can typically find this information through package managers, build scripts, or by querying the library directly via command-line tools.
Configuration Analysis: Verify if libcurl is built with the threaded resolver and eventfd support. This is commonly enabled on 64-bit architectures.
Application Behavior: Monitor applications using libcurl for unusual behavior, such as crashes or unresponsiveness, especially after DNS resolutions are completed.
Logging and Monitoring: Implement security logging to detect any double
close()calls on eventfd file descriptors. Look for any resource management-related errors that could indicate the vulnerability being triggered.Dependency Scanning: Tools like Software Composition Analysis (SCA) can scan your project dependencies and highlight the usage of vulnerable versions of libcurl.
How to Fix the Vulnerability?
Addressing CVE-2025-0665 requires a multi-faceted approach, including upgrading libcurl, implementing workarounds, and monitoring for potential exploitation.
Primary Remediation:
Upgrade libcurl: The most effective solution is to upgrade to libcurl version 8.12.0 or later. This version contains the fix that addresses the double close issue.
Apply the Patch: If upgrading is not immediately feasible, apply the patch (ff5091aa9f73802e894b1cbdf) to your current version of libcurl and rebuild the library.
Workarounds (If patching is not immediately possible):
Disable eventfd Use: If possible, disable eventfd support in your libcurl build. This will prevent the vulnerable code from being executed.
Use the c-ares Resolver Backend: Consider using the c-ares resolver backend as an alternative to the threaded resolver, as it does not rely on eventfd.
Additional Error Handling: Implement additional error handling and resource management checks in applications that use libcurl to mitigate potential crashes or instability.
Limit Threaded Name Resolves: If possible, limit the use of threaded name resolves in libcurl until a patch is confirmed.
Monitoring and Detection:
Implement Proper Logging and Monitoring: Set up comprehensive logging and vulnerability assessments to detect any unusual behavior or crashes related to this issue.
Monitor Security Advisories: Stay informed about any new developments or patches related to this vulnerability by monitoring official libcurl channels and security advisories.
By taking these steps, security professionals can effectively mitigate the risk posed by CVE-2025-0665 and ensure the stability and security of their applications and systems. It is crucial to prioritize patching and follow up with continuous monitoring to maintain a robust security posture.
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Arun KL
Arun KL is a cybersecurity professional with 15+ years of experience in IT infrastructure, cloud security, vulnerability management, Penetration Testing, security operations, and incident response. He is adept at designing and implementing robust security solutions to safeguard systems and data. Arun holds multiple industry certifications including CCNA, CCNA Security, RHCE, CEH, and AWS Security.
