CVE-2014-9116 in Mutt
Summary
by MITRE
The write_one_header function in mutt 1.5.23 does not properly handle newline characters at the beginning of a header, which allows remote attackers to cause a denial of service (crash) via a header with an empty body, which triggers a heap-based buffer overflow in the mutt_substrdup function.
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Analysis
by VulDB Data Team • 02/27/2022
The vulnerability identified as CVE-2014-9116 resides within the mutt email client version 1.5.23, specifically within the write_one_header function that processes email headers during message composition or display. This flaw represents a classic buffer overflow condition that occurs when the software fails to properly validate input data, particularly newline characters that appear at the beginning of email headers. The issue manifests when an attacker crafts a malicious email header containing an empty body, which then triggers an abnormal execution path in the mutt_substrdup function. The improper handling of these specific header sequences creates a condition where the application attempts to copy data into a buffer that is insufficiently sized to accommodate the input, resulting in memory corruption that leads to application instability.
The technical exploitation of this vulnerability follows a well-defined pattern that aligns with common software security flaws categorized under CWE-121, heap-based buffer overflow conditions. When mutt processes an email header beginning with newline characters, the write_one_header function does not adequately sanitize or validate the input sequence before passing it to mutt_substrdup. This function then attempts to duplicate the header content without proper bounds checking, causing memory corruption in the heap allocation. The vulnerability demonstrates characteristics consistent with CWE-787, out-of-bounds write conditions, where the application writes data beyond the allocated buffer boundaries. The flaw operates at the intersection of input validation and memory management, where insufficient boundary checks in the header processing pipeline create an exploitable condition that can be triggered remotely through crafted email content.
The operational impact of CVE-2014-9116 extends beyond simple denial of service, presenting significant risks to email server stability and user experience. When successfully exploited, the vulnerability causes mutt to crash and terminate unexpectedly, disrupting email communication services and potentially creating service availability issues for users relying on this email client. The remote nature of the attack means that adversaries can trigger the vulnerability without requiring local access to the target system, making it particularly concerning for email servers and clients that process untrusted email content. This type of vulnerability can be leveraged in larger attack campaigns where multiple systems are targeted, potentially leading to cascading failures in email infrastructure. The exploitability factor is relatively high given that email headers are routinely processed by email clients, and the condition can be triggered through simple email crafting techniques that do not require sophisticated attack infrastructure.
Mitigation strategies for CVE-2014-9116 should focus on both immediate patching and defensive measures. The most effective remediation involves upgrading to mutt version 1.5.24 or later, where the vulnerability has been addressed through proper input validation in the write_one_header function. Organizations should implement comprehensive email filtering and sanitization protocols that can detect and neutralize malformed headers before they reach vulnerable email clients. Network-based protections can include email header inspection rules that identify and block suspicious sequences of newline characters at the beginning of headers. System administrators should also consider implementing application-level sandboxing or containerization of email processing components to limit the impact of potential exploitation. Additionally, regular security assessments and vulnerability scanning should be conducted to identify similar issues in other email processing components, as this vulnerability demonstrates the importance of proper input validation in security-critical applications. The ATT&CK framework categorizes this vulnerability under T1203, Exploitation for Client Execution, where attackers leverage application flaws to cause unintended behavior in client software, making it a significant concern for enterprise email security policies.