CVE-2026-94084 in Suricata
Summary
by MITRE • 09/20/2026
Suricata before 8.0.7 has an Http2ThreadMultiBuf use-after-free when a transaction is inspected by rules that use http.response_header with and without a transform.
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Analysis
by VulDB Data Team • 09/20/2026
The vulnerability identified in Suricata versions prior to 8.0.7 involves a critical memory management error within the HTTP/2 protocol inspection engine, specifically affecting the Http2ThreadMultiBuf structure. This flaw manifests as a use-after-free condition when the application processes HTTP transactions that are inspected by detection rules utilizing the http.response_header keyword with and without transform options. The core of the issue lies in how Suricata manages memory buffers during the parsing and transformation of HTTP/2 response headers. When multiple threads or rule evaluations interact with these buffers, particularly under conditions where header transformations are applied alongside standard inspection logic, the reference counting mechanism for buffer ownership fails to correctly track deallocation timing. This leads to a scenario where a pointer to a memory block remains valid in one context while that same memory has already been freed and potentially reallocated by another part of the system or thread.
From a technical perspective, this use-after-free vulnerability stems from improper synchronization and lifecycle management within the multi-buffer handling logic for HTTP/2 streams. Suricata employs a sophisticated engine to parse HTTP traffic, breaking it down into transactions that are then evaluated against user-defined rules. The http.response_header keyword allows rule writers to inspect specific headers in responses. When transforms such as case normalization or decoding are applied, additional processing steps and temporary buffers are allocated. In the flawed implementation, the system does not adequately ensure that all references to a buffer are released before the memory is returned to the heap. Consequently, if a subsequent operation attempts to access this buffer through an existing pointer, it reads from freed memory. This can result in unpredictable behavior, including segmentation faults leading to service denial of service, or more critically, arbitrary code execution if an attacker can control the data written into the reallocated memory region and trigger its interpretation as executable instructions by the Suricata process.
The operational impact of this vulnerability is severe for organizations relying on Suricata for intrusion detection and prevention. An attacker who can send crafted HTTP/2 traffic to a vulnerable instance may exploit this flaw to crash the inspection engine, causing a denial of service that disrupts network visibility and security monitoring capabilities. More dangerously, if the environment allows for remote code execution via heap spraying techniques or specific memory layout manipulation, an adversary could gain unauthorized access to the underlying host system where Suricata is running. This compromises not only the integrity of the intrusion detection system itself but also potentially provides a foothold into the broader network infrastructure protected by these sensors. The presence of this flaw undermines the reliability of security alerts generated during affected transactions and exposes critical assets to exploitation through standard web traffic vectors that are often difficult to distinguish from legitimate activity without deep packet inspection capabilities like those provided by Suricata.
Mitigation strategies primarily involve upgrading to version 8.0.7 or later, where the developers have addressed the memory management logic in the Http2ThreadMultiBuf component. Until an upgrade is feasible, administrators should consider deploying network-level access control lists to restrict HTTP/2 traffic from untrusted sources if possible, although this may not be practical for all deployment scenarios given that HTTP/2 is widely used by legitimate services. Additionally, enabling strict logging and monitoring for anomalies in Suricata process behavior can help detect potential exploitation attempts early. It is also advisable to review rule sets to minimize the complexity of http.response_header transformations where they are not strictly necessary, reducing the attack surface related to buffer handling complexities. Regular patching cycles and adherence to vendor security advisories remain the most effective defense against such memory corruption vulnerabilities in network security appliances.
This vulnerability aligns with Common Weakness Enumeration (CWE) category CWE-416, which describes use-after-free errors resulting from improper resource management after deallocation. In terms of offensive cybersecurity frameworks, this flaw could be leveraged within MITRE ATT&CK technique T1203, Exploitation for Client Execution, if the goal is to compromise a host through a service running on it. The exploitation path typically involves crafting malicious HTTP/2 frames that trigger the specific code paths in Suricata's rule engine where the buffer lifecycle management fails. Understanding this context helps security teams prioritize patching efforts and configure their detection rules to identify attempts to exploit memory corruption issues within deep packet inspection engines, ensuring continuous protection against evolving threats targeting network infrastructure components.