CVE-2026-38638 in relibc
Summary
by MITRE • 08/28/2026
An issue in the with_argv function (/unistd/mod.rs) of relibc commit 61f42d allows attackers to cause a Denial of Service (DoS) via a crafted input.
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Analysis
by VulDB Data Team • 08/28/2026
The vulnerability identified within the relibc project, specifically located in the with_argv function found in the unistd/mod.rs module at commit 61f42d, represents a critical reliability flaw that can be exploited to induce a Denial of Service condition. Relibc serves as a minimal C standard library implementation designed for use in environments where traditional libc dependencies are unavailable or undesirable, such as embedded systems, operating system kernels, and secure enclaves. The with_argv function is responsible for managing the argument vector passed to an application during its initialization phase. This component plays a pivotal role in ensuring that command-line arguments are correctly parsed, validated, and stored before execution begins. When this function processes input data without adequate bounds checking or validation logic, it creates a pathway for attackers to disrupt system availability through malformed inputs.
The technical root of the vulnerability lies in improper handling of memory allocation or pointer dereferencing within the with_argv implementation. Specifically, when an attacker provides crafted input that exceeds expected limits or contains structurally invalid sequences, the function fails to gracefully handle these anomalies. Instead of returning an error code or safely truncating the input, the flawed logic may lead to out-of-bounds reads or writes, stack buffer overflows, or infinite loops depending on the specific implementation details of commit 61f42d. This lack of robustness means that a single maliciously constructed argument string can corrupt memory state or consume excessive computational resources, ultimately causing the application or system relying on relibc to crash or become unresponsive. Such behavior is particularly dangerous in server-side applications or long-running daemons where availability is paramount and unexpected termination leads to service disruption for end-users.
From an operational perspective, this vulnerability allows remote attackers who have access to supply command-line arguments or environment variables influencing the argv vector to trigger a denial of service. In web services that parse user-supplied parameters into system calls or child processes, an attacker could inject specially crafted strings via HTTP headers, query parameters, or file uploads if those inputs are eventually passed as program arguments. The impact extends beyond simple application crashes; in multi-tenant environments or containerized deployments, a single successful exploit can consume significant CPU and memory resources on the host node, potentially affecting other workloads sharing the same infrastructure. This aligns with common attack patterns where resource exhaustion is used to degrade service quality without necessarily gaining unauthorized access to data.
This flaw maps directly to CWE-20 Improper Input Validation, as the core issue stems from the failure to adequately sanitize and validate external input before processing it within critical system functions. Furthermore, the exploitation technique corresponds to ATT&CK T1499 Endpoint Denial of Service, which involves techniques designed to make software or hardware resources unavailable to legitimate users. By leveraging this vulnerability, an adversary can effectively neutralize a target service without needing elevated privileges or complex exploit chains, relying solely on the ability to influence input parameters. This makes it a low-effort, high-impact threat vector that should be prioritized for remediation in any deployment of relibc where external inputs are processed through argv-related functions.
Mitigation strategies must focus on hardening the with_argv function against malformed data. Developers should implement strict length checks to ensure input strings do not exceed predefined buffer limits before allocation or copying operations occur. Additionally, incorporating bounds checking mechanisms and using safe string handling libraries can prevent memory corruption issues associated with overflows. It is also advisable to add explicit error handling paths that return appropriate failure codes rather than proceeding with invalid data structures. For organizations currently running affected versions of relibc, immediate patching to a version where this commit has been addressed or superseded by more robust implementations is essential. In the interim, deploying input validation filters at the network perimeter or application gateway level can help block malicious payloads before they reach the vulnerable component, providing an additional layer of defense against exploitation attempts targeting command-line argument processing mechanisms.