Horizon Alert
Summary of the vulnerability and why it matters
A flaw in the widely used libcurl data transfer library could allow applications to send incorrect data or encounter memory issues when reusing a connection handle. This occurs under specific conditions where a previous PUT request using a read callback is followed by a POST request. While the library is common, the specific scenario needed to trigger this vulnerability means its direct impact on publicly accessible services is unlikely, though it could affect internal applications.
- Incorrect data or memory issues in data transfers.
- Concerns about how applications reuse connection handles.
- Confirm relevance and exposure within internal systems.
Attack Path
How an attacker could exploit the issue
An attacker could exploit this vulnerability by tricking an application that uses a specific version of the curl library into reusing a network connection handle. If this handle was previously used for a PUT request that utilized a read callback function, and is later reused for a POST request without the read callback, the application might mistakenly use the callback to send data. This misbehavior could lead to the transmission of incorrect data or memory corruption issues.
- Application must reuse a network handle.
- Handle must transition from PUT with callback to POST.
- Incorrect data sent or memory corruption.
Live Threat
Current exploitation, exposure, and threat context
When a libcurl handle is reused for a POST request after a PUT request that used a read callback, it could erroneously use the read callback to send data, potentially leading to the transmission of incorrect information or memory corruption. This occurs due to a flaw in the handle's state management when transitioning between request types.
- Sensitive data or system information may be exposed.
- Incorrect data sent or memory corruption.
- Application misbehavior or data leakage.
Operational Fix
Recommended remediation, mitigation, and detection steps
This vulnerability is likely to impact applications that utilize the libcurl library for HTTP(S) transfers, particularly those that reuse handles across different request methods (PUT to POST) and employ custom read callbacks. Application owners, development teams, and potentially platform or infrastructure teams responsible for managing dependencies are the primary actors. The first practical step involves identifying all deployments of affected applications, verifying if they are externally reachable or handle critical data, and confirming the responsible ownership for each instance before planning remediation.
- Application owners should address this issue.
- Verify external reachability and data criticality.
- Plan remediation considering application dependencies.
