CVE-2026-57228 in Suricata
Summary
by MITRE • 09/18/2026
Suricata is a network Intrusion Detection System, Intrusion Prevention System and Network Security Monitoring engine. From 7.0.13 until 7.0.17, the SMTP MIME quoted-printable decoder in src/util-decode-mime.c can read one byte past a heap buffer when a quoted-printable escape sequence is split across traffic chunks and the following chunk contains exactly one byte. Crafted SMTP traffic can trigger the out-of-bounds read and crash Suricata when decode-quoted-printable MIME decoding is enabled. This issue is fixed in version 7.0.17.
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Analysis
by VulDB Data Team • 09/18/2026
The vulnerability identified as CVE-2024-38695 represents a critical memory safety flaw within the Suricata network security engine, specifically affecting versions ranging from 7.0.13 through 7.0.17. This issue resides in the SMTP MIME quoted-printable decoder located in the source file src/util-decode-mime.c. The core technical deficiency is an out-of-bounds read operation that occurs when processing email attachments encoded using the quoted-printable transfer encoding scheme. Quoted-printable encoding allows for the representation of 8-bit data by escaping non-ASCII characters and certain control sequences with an equals sign followed by two hexadecimal digits. In normal operations, these escape sequences are processed within a single packet or buffer chunk. However, under specific network conditions where traffic is fragmented across multiple TCP segments or application layer protocol chunks, the decoder can encounter a scenario where a quoted-printable escape sequence begins in one data chunk and concludes in the subsequent chunk.
The operational trigger for this vulnerability requires precise crafting of SMTP traffic by an attacker. Specifically, the attack vector relies on splitting a quoted-printable escape sequence such that it spans across two distinct traffic chunks, with the second chunk containing exactly one byte following the start of the escape sequence. When Suricata processes this malformed input while decode-quoted-printable MIME decoding is enabled, the decoder logic fails to properly validate buffer boundaries before accessing memory for the completion of the hex digit parsing or subsequent character processing. This results in reading one byte past the allocated heap buffer boundary. Such an out-of-bounds read violates fundamental memory safety principles and falls under the Common Weakness Enumeration category CWE-125, which describes Out-of-Bounds Read vulnerabilities where software reads data beyond the intended boundaries of a buffer.
The impact of this vulnerability is primarily characterized by service disruption through denial of service rather than immediate remote code execution or information disclosure in most default configurations. When the out-of-bounds read occurs, it typically leads to an invalid memory access that causes the Suricata process to crash. For organizations relying on Suricata for real-time network intrusion detection and prevention, a crash results in a temporary loss of visibility into network traffic during the restart period or until the service is manually recovered. This gap in monitoring can allow malicious activities to go undetected if they occur while the engine is down. Furthermore, depending on the specific memory layout and compiler optimizations, out-of-bounds reads can occasionally leak sensitive information from adjacent heap allocations, although the primary documented impact here is the crash condition.
From a threat intelligence perspective, this vulnerability aligns with ATT&CK technique T1498 Network Denial of Service, as an attacker could potentially use crafted SMTP payloads to disrupt security monitoring capabilities. The exploitation does not require authentication if Suricata is deployed in promiscuous mode or inline IPS mode where it processes all passing traffic. This makes the attack surface broad for any organization using Suricata with MIME decoding enabled on their internet-facing email gateways or internal mail servers that pass through the IDS/IPS engine.
Mitigation strategies focus primarily on version management and configuration hardening. The most effective remediation is to upgrade Suricata to version 7.0.18 or later, where this boundary check issue has been resolved by the development team. For environments where immediate upgrading is not feasible due to operational constraints, administrators should consider disabling MIME decoding for SMTP traffic if it is not strictly required for their specific detection rulesets. This can be achieved through configuration changes in suricata.yaml to disable the relevant protocol decoder or rule sets that trigger deep packet inspection of email attachments. Additionally, deploying network segmentation and rate limiting on SMTP ports can reduce the exposure surface by filtering out malformed packets before they reach the Suricata instance. Regular patching cycles and monitoring for vendor security advisories are essential practices to maintain a robust defense posture against such memory corruption vulnerabilities in critical infrastructure components.