CVE-2026-67297 in FreeRDP
Summary
by MITRE • 08/01/2026
FreeRDP before 3.29.0 fails to enforce the RESPONSE_SIZE_LIMIT when processing Transfer-Encoding: chunked HTTP responses in http_response_recv_body(). Attackers controlling a malicious RD Gateway endpoint can send oversized chunked response bodies to exhaust client memory resources without triggering the configured size limit.
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Analysis
by VulDB Data Team • 08/01/2026
This vulnerability exists within FreeRDP versions prior to 3.29.0 where the software fails to properly enforce the RESPONSE_SIZE_LIMIT parameter when handling Transfer-Encoding: chunked HTTP responses through the http_response_recv_body() function. The flaw allows attackers who control a malicious RD Gateway endpoint to craft oversized chunked response bodies that can exhaust client memory resources without triggering the configured size limits, potentially leading to denial of service conditions or resource exhaustion attacks. The issue stems from improper validation of chunked transfer encoding boundaries and lack of proper size enforcement during HTTP response processing.
The technical implementation of this vulnerability involves the failure to validate chunked response sizes against configured limits during HTTP body reception. When FreeRDP processes chunked HTTP responses, it should enforce the RESPONSE_SIZE_LIMIT to prevent memory exhaustion attacks by limiting the total size of received data. However, the http_response_recv_body() function does not properly check chunk boundaries or accumulate chunk sizes against the configured limit, allowing attackers to send multiple chunks that collectively exceed the intended memory constraints without triggering any size violation checks.
This vulnerability has significant operational impact on systems using FreeRDP clients, particularly those connecting through RD Gateway services where attackers can potentially compromise client systems through memory exhaustion attacks. The flaw enables remote attackers to consume excessive memory resources on client machines, leading to system instability, application crashes, or complete denial of service conditions that prevent legitimate users from accessing remote desktop services. Organizations relying on FreeRDP for remote access may face service disruption and increased attack surface exposure.
The vulnerability aligns with CWE-400 which addresses unrestricted resource consumption, specifically targeting memory exhaustion issues in network protocol implementations. From an ATT&CK framework perspective, this represents a denial of service technique that can be leveraged as part of initial access or persistence phases where attackers seek to compromise system availability. The flaw also connects to CWE-129 which covers improper validation of length before using data in memory operations, since the software fails to validate chunked response lengths against configured security boundaries.
Mitigation strategies should include immediate upgrade to FreeRDP version 3.29.0 or later where the RESPONSE_SIZE_LIMIT enforcement has been properly implemented for chunked HTTP responses. Organizations should also consider implementing network-level controls such as rate limiting and connection monitoring to detect unusual patterns of chunked response processing. Additional defensive measures include configuring stricter memory limits on client systems, enabling intrusion detection systems to monitor for abnormal chunked transfer activity, and implementing proper input validation at multiple layers of the network stack to prevent oversized data from being processed by vulnerable components.
The fix implemented in FreeRDP 3.29.0 addresses the core issue by ensuring that chunked response processing properly enforces configured size limits through enhanced validation logic in the http_response_recv_body() function. This update implements proper cumulative size tracking for chunked responses and ensures that any attempt to exceed the RESPONSE_SIZE_LIMIT triggers appropriate error handling rather than allowing memory exhaustion to occur. The patch also includes additional checks for malformed chunk boundaries and improved resource management during HTTP response processing.
Organizations should conduct comprehensive security assessments of their FreeRDP deployments to identify systems running vulnerable versions and ensure proper patching procedures are followed across all client installations. Regular monitoring of network traffic patterns can help detect potential exploitation attempts, while maintaining updated threat intelligence feeds will provide early warning of similar vulnerabilities in related software components. The vulnerability highlights the importance of proper input validation in protocol implementations and demonstrates how seemingly minor implementation flaws in HTTP handling code can lead to significant security implications in remote access systems.
This issue represents a classic example of how insufficient boundary checking in network protocol implementations can create exploitable conditions for memory exhaustion attacks, particularly in client-side applications that process untrusted network data. The vulnerability underscores the necessity of implementing robust size validation mechanisms and proper resource management in all components handling external data streams, especially those operating in security-sensitive environments where denial of service conditions can have serious operational consequences.