CVE-2022-32221: Haxx Curl Use-After-Free Vulnerability

CVE-2022-32221 Overview

CVE-2022-32221 is a critical vulnerability in libcurl affecting HTTP(S) transfers where the library may erroneously use the read callback (CURLOPT_READFUNCTION) to request data to send, even when the CURLOPT_POSTFIELDS option has been set. This condition occurs when the same handle was previously used to issue a PUT request that utilized that callback. The flaw can cause applications to misbehave, potentially sending incorrect data or triggering use-after-free conditions in subsequent POST requests.

Critical Impact

This vulnerability can lead to information disclosure, use-after-free memory corruption, and potential remote code execution through malformed HTTP request handling when reusing curl handles across PUT and POST operations.

Affected Products

• Haxx curl (versions prior to the security fix)
• NetApp Clustered Data ONTAP
• NetApp H300S, H500S, H700S, H410S Firmware
• Debian Linux 10.0 and 11.0
• Apple macOS
• Splunk Universal Forwarder

Discovery Timeline

• 2022-12-05 - CVE-2022-32221 published to NVD
• 2026-02-13 - Last updated in NVD database

Technical Details for CVE-2022-32221

Vulnerability Analysis

The vulnerability exists in the handle reuse logic within libcurl when transitioning between HTTP methods. When an application reuses a curl handle that was previously configured for a PUT request with a custom read callback (CURLOPT_READFUNCTION), and then reconfigures it for a POST request using CURLOPT_POSTFIELDS, libcurl may incorrectly continue to invoke the previously registered read callback instead of using the statically provided POST data.

This creates a dangerous state where the application's read callback function may be invoked unexpectedly, potentially accessing memory that has already been freed or returning unintended data. The vulnerability is classified under CWE-200 (Exposure of Sensitive Information to an Unauthorized Actor) and CWE-668 (Exposure of Resource to Wrong Sphere), reflecting its potential for both information disclosure and improper resource handling.

Root Cause

The root cause lies in improper state management when transitioning a reused curl handle from a PUT request to a POST request. The internal state tracking for the data source mechanism fails to properly reset or override the read callback configuration when CURLOPT_POSTFIELDS is set on a handle that previously used CURLOPT_READFUNCTION. This results in the library maintaining stale callback references that should have been cleared during the method transition.

Attack Vector

The attack vector is network-based and can be exploited without user interaction or authentication. An attacker could potentially exploit this vulnerability in scenarios where:

1. An application reuses curl handles for multiple HTTP operations (a common performance optimization)
2. The application performs PUT requests followed by POST requests on the same handle
3. The application uses custom read callbacks for PUT operations

The vulnerability manifests when the callback mechanism reads from freed memory regions or when sensitive data from unrelated memory regions is inadvertently included in HTTP requests. This could result in information leakage to remote servers or corruption of memory leading to arbitrary code execution.

The technical details of the exploitation are documented in the HackerOne Security Report #1704017, which provides the original vulnerability disclosure information.

Detection Methods for CVE-2022-32221

Indicators of Compromise

• Unexpected memory access patterns in applications using libcurl with handle reuse
• Anomalous HTTP POST request payloads that differ from expected application data
• Application crashes or segmentation faults during HTTP operations following PUT-to-POST handle transitions
• Memory corruption indicators in curl-dependent processes

Detection Strategies

• Monitor for curl library versions prior to the patched release across infrastructure
• Implement application-level logging to track curl handle reuse patterns and HTTP method transitions
• Deploy memory corruption detection tools (AddressSanitizer, Valgrind) in development and testing environments
• Analyze outbound HTTP traffic for unexpected or malformed POST request bodies

Monitoring Recommendations

• Enable verbose logging in applications using libcurl to capture handle lifecycle events
• Implement network traffic analysis to detect anomalous data patterns in HTTP requests
• Monitor system logs for segmentation faults or memory errors in processes using curl
• Use endpoint detection and response (EDR) solutions to identify exploitation attempts

How to Mitigate CVE-2022-32221

Immediate Actions Required

• Update libcurl to the latest patched version immediately across all systems
• Identify all applications and systems using affected curl versions
• Review application code for curl handle reuse patterns, particularly PUT-to-POST transitions
• Consider isolating systems running vulnerable versions until patches can be applied

Patch Information

Security patches have been released by multiple vendors. Organizations should apply the appropriate updates:

• Debian: Apply updates from Debian Security Advisory DSA-5330 and Debian LTS Security Announcement
• Gentoo: Apply Gentoo GLSA 2022-12-01
• NetApp: Refer to NetApp Security Advisory NTAP-20230110-0006 and NTAP-20230208-0002
• Apple macOS: Apply updates from Apple Support HT213604 and HT213605

Workarounds

• Avoid reusing curl handles between PUT and POST operations until patching is complete
• Create new curl handles for each HTTP request as a temporary mitigation
• Explicitly reset all options on curl handles before reuse using curl_easy_reset()
• Implement application-level validation of POST data before transmission

# Check curl version on Linux systems
curl --version

# Update curl on Debian/Ubuntu systems
sudo apt-get update && sudo apt-get upgrade curl libcurl4

# Update curl on RHEL/CentOS systems
sudo yum update curl libcurl