CVE-2023-28322: Haxx Curl Information Disclosure Flaw

CVE-2023-28322 Overview

An information disclosure vulnerability exists in curl versions prior to v8.1.0 when performing HTTP(S) transfers. The vulnerability occurs when libcurl erroneously uses the read callback (CURLOPT_READFUNCTION) to request data to send, even when the CURLOPT_POSTFIELDS option has been set. This behavior manifests when the same handle was previously used to issue a PUT request that utilized that callback. The flaw may cause applications to misbehave, potentially sending incorrect data or accessing memory after it has been freed in subsequent transfers.

Critical Impact

Applications reusing curl handles for HTTP method transitions from PUT to POST may inadvertently leak sensitive data or experience use-after-free conditions due to improper callback handling.

Affected Products

• Haxx curl (versions prior to 8.1.0)
• Apple macOS
• Fedora (versions 37, 38)
• NetApp Clustered Data ONTAP
• NetApp ONTAP Antivirus Connector
• NetApp H300S, H500S, H700S, H410S (firmware and hardware)

Discovery Timeline

• 2023-05-26 - CVE-2023-28322 published to NVD
• 2024-11-21 - Last updated in NVD database

Technical Details for CVE-2023-28322

Vulnerability Analysis

This vulnerability represents an information disclosure issue (CWE-200) that stems from improper state management in libcurl's handle reuse logic. When a curl handle is reused across multiple HTTP requests, the library must properly reset and reconfigure internal state to match the new request type. The flaw occurs specifically in the transition from a PUT request to a POST request when certain callback options are involved.

The problem manifests when an application first performs a PUT request using CURLOPT_READFUNCTION to provide the request body data via a callback, then subsequently reuses the same handle for a POST request configured with CURLOPT_POSTFIELDS to provide static data. Due to the logic error, libcurl may incorrectly invoke the read callback from the previous PUT request instead of using the configured POST fields data.

Root Cause

The root cause lies in the handle reuse logic within libcurl that fails to properly clear or override the read callback configuration when transitioning between HTTP methods. When a handle is configured for a PUT request with CURLOPT_READFUNCTION, this callback registration persists even when the handle is reconfigured for a POST request with CURLOPT_POSTFIELDS. The internal state machine does not properly prioritize the CURLOPT_POSTFIELDS setting over the previously registered callback.

Attack Vector

The vulnerability requires network access and specific application behavior to exploit. An attacker would need to identify applications that:

1. Reuse curl handles across multiple HTTP requests
2. Transition from PUT requests using read callbacks to POST requests using post fields
3. Process the potentially corrupted or leaked data in a security-sensitive context

The exploitation scenario involves the application inadvertently sending data from the wrong source, which could include:

• Sending stale or freed memory contents as request data
• Leaking sensitive information from previous requests
• Causing application crashes due to use-after-free conditions

Since exploitation requires specific application behavior patterns and the vulnerability does not allow direct attacker control, the attack complexity is high. The issue primarily affects confidentiality through potential information exposure.

Detection Methods for CVE-2023-28322

Indicators of Compromise

• Unexpected HTTP POST request bodies that do not match intended CURLOPT_POSTFIELDS content
• Application crashes or memory errors during HTTP request processing involving handle reuse
• Anomalous data patterns in outbound HTTP POST requests following PUT operations

Detection Strategies

• Monitor applications using libcurl for unexpected memory access patterns during HTTP request handling
• Implement application-level logging to track curl handle reuse patterns, especially PUT to POST transitions
• Deploy runtime memory analysis tools to detect potential use-after-free conditions in applications using curl
• Audit application code for patterns that reuse curl handles across different HTTP methods with mixed callback configurations

Monitoring Recommendations

• Enable verbose logging in curl-dependent applications to trace HTTP method transitions and callback invocations
• Implement network-level inspection to detect anomalous or malformed POST request bodies
• Set up alerts for application errors related to curl handle operations or memory access violations
• Review system logs for crash reports associated with applications that heavily use libcurl for HTTP operations

How to Mitigate CVE-2023-28322

Immediate Actions Required

• Upgrade curl to version 8.1.0 or later where this vulnerability has been addressed
• Audit applications for patterns that reuse curl handles across PUT and POST requests
• Consider using separate curl handles for different HTTP methods as a temporary mitigation
• Review and apply vendor-specific patches from Apple, NetApp, Fedora, and other affected vendors

Patch Information

The vulnerability was fixed in curl version 8.1.0. Multiple vendors have released security updates addressing this issue:

• Apple: Security updates available via Apple Support Article HT213843, HT213844, and HT213845
• Fedora: Package updates available through Fedora Package Announcement
• NetApp: Advisory NTAP-20230609-0009 provides guidance for affected products
• Gentoo: Security advisory GLSA 202310-12 addresses this vulnerability
• Debian: Updates available per Debian LTS Announcement

Additional technical details are available in the HackerOne Report #1954658.

Workarounds

• Avoid reusing curl handles when transitioning between PUT and POST requests; create fresh handles for each request type
• Explicitly reset curl handles using curl_easy_reset() before reconfiguring for a different HTTP method
• Clear all callback-related options before setting CURLOPT_POSTFIELDS on a reused handle
• Consider implementing application-level validation to verify request body content matches intended data before transmission

# Verification: Check installed curl version
curl --version

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

# Update curl on RHEL/Fedora systems
sudo dnf update curl libcurl

# Update curl on macOS via Homebrew
brew upgrade curl