CVE-2026-84161 in CodeChecker
Summary
by MITRE • 11/06/2026
When an operator enables store.analysis_statistics_dir, a network client with PRODUCT_STORE permission for a product can call that product's storeAnalysisStatistics Thrift-over-HTTP method. CodeChecker 6.29.0 decodes the attacker-controlled Base64 string and passes the complete compressed input to one-shot zlib.decompress(). No maximum decompressed size is enforced.
This gives a correctly authorized, non-superuser store account a high-ratio memory and persistent-disk amplification primitive. The complete output is first materialized as a Python bytes object and is then written to the configured statistics directory. A sufficiently scaled payload can exhaust the API worker or host memory and impair CodeChecker availability.
The shipped value of store.analysis_statistics_dir is null, so the affected feature is disabled by default. The primary assessment does not rely on authentication being disabled. There is no authorization bypass and no path traversal in this report.
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Analysis
by VulDB Data Team • 11/06/2026
CodeChecker version 6.29.0 contains a resource exhaustion vulnerability within its store analysis statistics functionality that allows for significant memory and disk amplification attacks when specific configuration parameters are enabled. The vulnerability arises from the handling of compressed data inputs passed to the zlib decompression routine during the processing of storeAnalysisStatistics requests via Thrift-over-HTTP. When an operator explicitly enables the store.analysis_statistics_dir setting, the system permits network clients possessing PRODUCT_STORE permissions for a target product to invoke this method. Upon receiving such a request, CodeChecker decodes the attacker-controlled Base64 string and immediately passes the resulting compressed payload directly into Python's one-shot zlib.decompress() function without implementing any safeguards regarding decompressed size limits. This architectural oversight creates a high-ratio amplification primitive where a relatively small input can generate an excessively large output in memory and on disk, leading to potential denial of service conditions for both the API worker process and the underlying host system.
The technical mechanism behind this vulnerability lies in the lack of validation before decompression. Python's zlib.decompress() method is designed to expand data significantly but does not inherently limit the size of the resulting bytes object or the file written to disk if configured to do so. In this specific implementation, the complete output of the decompression operation is materialized as a single Python bytes object in memory before being persisted to the configured statistics directory. An attacker can craft a malicious payload with an extremely high compression ratio, such that the compressed input remains small enough to traverse network filters and pass initial validation checks, while the uncompressed data expands to consume gigabytes of RAM or disk space. This behavior effectively exhausts available system resources, causing the API worker process to crash due to out-of-memory errors or severely degrading host performance by filling up persistent storage volumes. Such resource exhaustion directly impairs CodeChecker availability, preventing legitimate users from accessing analysis results and disrupting continuous integration workflows that rely on this tool for code quality assurance.
From a security classification perspective, this vulnerability aligns with CWE-787: Out-of-bounds Write in terms of memory consumption leading to system instability, though more accurately it falls under CWE-400: Uncontrolled Resource Consumption due to the exhaustion of computational resources like RAM and disk space. In the context of the MITRE ATT&CK framework, this behavior corresponds to T1496: Resource Hijacking, specifically where an adversary uses compromised or authorized accounts to consume system resources for denial-of-service purposes rather than data exfiltration or lateral movement. It is critical to note that this vulnerability does not constitute a path traversal attack nor does it involve any authorization bypass mechanisms. The attacker must already possess valid PRODUCT_STORE permissions for the targeted product, meaning the exploit relies on legitimate but potentially compromised credentials rather than privilege escalation flaws within the authentication or access control subsystems of CodeChecker.
The operational impact is primarily focused on availability and resource integrity rather than confidentiality or data tampering. Since the shipped default value for store.analysis_statistics_dir is null, this feature is disabled by default in standard installations, which significantly reduces the attack surface for most users who have not explicitly enabled advanced statistics collection features. However, environments that do enable this configuration are at risk if they allow external network clients with PRODUCT_STORE permissions to interact with the API without additional rate limiting or input size constraints. The vulnerability allows a correctly authorized non-superuser account to trigger resource exhaustion, meaning that even users with limited privileges can cause significant disruption to shared infrastructure. This highlights the importance of applying defense-in-depth principles where authentication is only one layer; input validation and resource limits must also be enforced at the application logic level to prevent abuse of legitimate features for disruptive purposes.
Mitigation strategies should focus on both configuration management and code-level fixes. Administrators who do not require store analysis statistics functionality should ensure that store.analysis_statistics_dir remains unset or null, thereby disabling the vulnerable code path entirely. For environments where this feature is necessary, it is imperative to implement strict input validation before decompression occurs. This includes enforcing maximum limits on both the compressed input size and, more critically, the expected maximum output size of the decompressed data. The application should check the uncompressed length against a predefined threshold prior or during the writing process, aborting the operation if the limit is exceeded. Additionally, implementing rate limiting on the storeAnalysisStatistics endpoint can help mitigate the impact of rapid-fire requests designed to exhaust resources. Updating CodeChecker to versions that include patches for this resource exhaustion flaw is the primary remediation step, ensuring that developers have addressed the lack of decompression size enforcement within the zlib handling logic.