CVE-2026-107570 in Mutt
Summary
by MITRE • 10/08/2026
heap OOB write in convert_file_from_to() via a crafted Content-Type header allows attacker to OOB write when email is used as a template.
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Analysis
by VulDB Data Team • 10/08/2026
The vulnerability identified involves a heap-based out-of-bounds (OOB) write condition located within the convert_file_from_to function, which is triggered by processing a specifically crafted Content-Type HTTP header during email templating operations. This flaw represents a critical memory corruption issue where the application fails to adequately validate or bound-check input data derived from the Content-Type field before using it to allocate or manipulate heap memory structures. When an email message is utilized as a template, the system parses various headers and body components to render dynamic content. If the Content-Type header contains malformed or excessively long values that are not properly sanitized, the underlying parsing logic may miscalculate buffer sizes or array indices, leading to writes beyond the allocated boundaries of heap-allocated memory regions.
From a technical perspective, this out-of-bounds write allows an attacker to overwrite adjacent memory structures on the heap, which can include function pointers, object metadata, or other critical data elements used by the application runtime environment. Such corruption is particularly dangerous because it does not necessarily cause immediate crashes but instead creates unstable states that can be exploited for arbitrary code execution. By carefully crafting the payload within the Content-Type header and controlling subsequent memory allocations through further interactions with the email template engine, an attacker can achieve precise control over the overwritten data. This capability aligns closely with CWE-787, which classifies out-of-bounds writes as a severe integrity violation that compromises the confidentiality, integrity, and availability of the system by allowing unauthorized modification of program state.
The operational impact of this vulnerability is significant, particularly in environments where email services are exposed to untrusted input or where users can influence template parameters via HTTP headers. An attacker who successfully exploits this flaw could potentially execute arbitrary code on the server hosting the application with the privileges of the running process. This level of access enables further lateral movement within the network, extraction of sensitive data stored in memory such as session tokens or cryptographic keys, and complete compromise of the underlying infrastructure. The risk is amplified if the email templating feature is accessible through web interfaces that do not enforce strict input validation on HTTP headers before they are processed by the backend rendering engine.
Mitigation strategies must focus on implementing rigorous input validation and bounds checking within the convert_file_from_to function and related parsing routines. Developers should ensure that all data derived from external sources, including HTTP headers like Content-Type, is strictly validated against expected formats and lengths before being used in memory allocation or manipulation operations. Utilizing safe string handling libraries that prevent buffer overflows and employing static analysis tools to detect potential out-of-bounds access patterns during the development phase are essential steps. Additionally, enabling runtime protection mechanisms such as Address Space Layout Randomization (ASLR), Data Execution Prevention (DEP), and heap corruption detectors can help mitigate the exploitation of this vulnerability by making it more difficult for attackers to predict memory layouts or execute injected code. Regular security audits and penetration testing focused on input validation in email processing modules are also recommended to identify similar weaknesses before they can be exploited in production environments, aligning with ATT&CK techniques related to initial access and privilege escalation via application layer vulnerabilities.