CVE-2018-16839 in cURL
Summary
by MITRE
Curl versions 7.33.0 through 7.61.1 are vulnerable to a buffer overrun in the SASL authentication code that may lead to denial of service.
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Analysis
by VulDB Data Team • 06/04/2023
The vulnerability identified as CVE-2018-16839 represents a critical buffer overrun flaw within the curl library's Simple Authentication and Security Layer implementation. This issue affects curl versions ranging from 7.33.0 through 7.61.1, creating a significant security risk that could be exploited to disrupt service availability. The buffer overrun occurs specifically within the SASL authentication code path, where improper input validation and memory management practices create opportunities for malicious actors to manipulate the authentication process.
The technical flaw manifests when curl processes SASL authentication mechanisms, particularly during the handling of authentication credentials or negotiation sequences. The vulnerability stems from inadequate bounds checking in the buffer management routines that process authentication data, allowing attackers to provide specially crafted inputs that exceed allocated buffer boundaries. This condition can result in memory corruption that may manifest as program termination, stack corruption, or potentially arbitrary code execution depending on the specific environment and exploitation vector. The flaw aligns with CWE-121, which describes stack-based buffer overflow conditions, and CWE-122, which covers heap-based buffer overflow scenarios that can occur during dynamic memory allocation.
From an operational impact perspective, this vulnerability creates substantial risks for systems relying on curl for network communications, particularly those handling authentication with external services. The denial of service aspect means that adversaries could disrupt legitimate service operations by triggering the buffer overrun through crafted authentication requests, effectively preventing authorized users from accessing network resources. This vulnerability is particularly concerning in environments where curl is used extensively for automated processes, web scraping, or API communications where authentication is frequently required. The impact extends beyond simple service disruption to potentially compromise the integrity of authentication flows that rely on curl's SASL implementation.
The exploitation of this vulnerability requires minimal privileges and can be executed through standard network-based attacks targeting services that utilize curl for authentication. Attackers need only craft specific authentication requests that trigger the buffer overrun condition within the SASL code path. This makes the vulnerability particularly dangerous as it can be exploited by attackers with limited access to the network, potentially leading to widespread service disruption across multiple systems that depend on curl for network operations. Organizations should consider this vulnerability in their threat modeling and incident response planning, as it represents a straightforward path to service disruption that could be weaponized in larger attack campaigns.
Mitigation strategies for CVE-2018-16839 primarily involve immediate patching of affected curl installations to versions that contain the necessary buffer overflow protections and input validation improvements. System administrators should prioritize updating curl libraries across all affected systems, particularly those handling external authentication or network communications. Additional mitigations include implementing network segmentation to limit exposure of systems using curl for authentication, monitoring network traffic for suspicious authentication patterns, and deploying intrusion detection systems that can identify potential exploitation attempts. Organizations should also consider temporary workarounds such as disabling SASL authentication mechanisms when not required, though this approach may impact legitimate service functionality. The remediation process should follow standard security patch management procedures, including testing patches in controlled environments before widespread deployment to ensure compatibility with existing applications and services that depend on curl functionality.