Overview
CVE-2025-63938 is a medium-severity integer overflow vulnerability affecting Tinyproxy versions up to 1.11.2. This flaw resides within the strip_return_port() function in the src/reqs.c file. A malicious actor could potentially exploit this vulnerability to cause a denial-of-service (DoS) condition or, in more complex scenarios, achieve arbitrary code execution. It is crucial to understand the details of this vulnerability and apply the necessary mitigations to protect your Tinyproxy instances.
Technical Details
The vulnerability lies within the strip_return_port() function, which is responsible for parsing and processing the port number from a client’s request. Due to insufficient validation, a specially crafted request containing an excessively large port number can trigger an integer overflow. This overflow leads to unexpected behavior, potentially corrupting memory or causing the application to crash. The exact nature of the overflow and its impact are further documented in the provided references.
Specifically, the integer overflow occurs during the calculation of memory allocation size based on the provided port number. If the resulting calculated size wraps around due to the overflow, a smaller-than-expected buffer will be allocated. Subsequently, when data is written to this undersized buffer, a heap overflow occurs.
CVSS Analysis
- CVE ID: CVE-2025-63938
- Severity: MEDIUM
- CVSS Score: 6.5
A CVSS score of 6.5 indicates a medium severity vulnerability. While the vulnerability might not be directly exploitable for remote code execution in all environments, the potential for denial-of-service is significant. The attack complexity is moderate, requiring some degree of crafted input, and the potential impact includes loss of availability and potential data integrity issues.
Possible Impact
The exploitation of CVE-2025-63938 can lead to several negative consequences:
- Denial of Service (DoS): The most likely outcome is a crash of the Tinyproxy service, rendering it unavailable to legitimate users.
- Memory Corruption: The integer overflow can corrupt memory, potentially leading to unpredictable behavior and instability.
- Potential Code Execution (Less Likely): While less probable, a skilled attacker might be able to leverage the memory corruption to achieve arbitrary code execution, depending on the system architecture and configuration.
Mitigation and Patch Steps
The most effective mitigation is to upgrade your Tinyproxy installation to a version that includes the fix for CVE-2025-63938. This fix is available in versions greater than 1.11.2. Here are the steps you should take:
- Upgrade Tinyproxy: Download and install the latest version of Tinyproxy from the official website or your distribution’s package manager.
- Verify the Patch: Ensure that the version you install includes the commit 3c0fde94981b025271ffa1788ae425257841bf5a. This commit addresses the integer overflow vulnerability in
src/reqs.c. - Monitor Your System: Continuously monitor your Tinyproxy instance for any signs of anomalous behavior, such as crashes or unexpected resource consumption.
