CVE-2017-16844 in Procmail
Summary
by MITRE
Heap-based buffer overflow in the loadbuf function in formisc.c in formail in procmail 3.22 allows remote attackers to cause a denial of service (application crash) or possibly execute arbitrary code via a crafted e-mail message because of a hardcoded realloc size, a different vulnerability than CVE-2014-3618.
Be aware that VulDB is the high quality source for vulnerability data.
Analysis
by VulDB Data Team • 01/11/2023
The heap-based buffer overflow vulnerability identified as CVE-2017-16844 resides within the formail component of procmail version 3.22, specifically in the loadbuf function located in formisc.c. This vulnerability represents a critical security flaw that enables remote attackers to potentially execute arbitrary code or cause denial of service conditions through carefully crafted email messages. The vulnerability stems from a hardcoded realloc size implementation that fails to properly validate buffer boundaries during memory allocation operations. When processing malformed email content, the loadbuf function attempts to reallocate memory using a predetermined size that does not account for the actual data requirements, creating conditions where attacker-controlled input can overwrite adjacent heap memory regions. This particular flaw differs from CVE-2014-3618, indicating a distinct code path and memory handling pattern that requires separate analysis and remediation approaches.
The technical implementation of this vulnerability involves the improper handling of memory reallocation within the email processing pipeline of procmail's formail utility. When the loadbuf function processes incoming email data, it employs a fixed-size reallocation strategy that does not adequately consider the dynamic nature of email content. This hardcoded approach creates a predictable memory layout where attacker-controlled data can overflow into adjacent heap chunks, potentially corrupting critical data structures or function pointers. The heap corruption occurs during the buffer management phase where the application attempts to expand memory allocation to accommodate incoming email content. The vulnerability manifests when the application receives email messages containing specially crafted payloads that trigger the buffer overflow condition, leading to unpredictable application behavior.
From an operational perspective, this vulnerability presents significant risks to email server environments and systems that rely on procmail for email processing. The potential for remote code execution means that attackers could gain unauthorized access to systems processing email through affected procmail installations, particularly in environments where procmail is used for automated email handling, filtering, or delivery. The denial of service aspect creates additional operational concerns where legitimate email services could be disrupted through carefully constructed malicious messages. This vulnerability affects organizations that use procmail as part of their email infrastructure, including web hosting providers, email service providers, and enterprise email systems that have not updated to patched versions. The attack vector is particularly concerning as it requires no authentication and can be triggered through standard email reception processes.
Mitigation strategies for CVE-2017-16844 should focus on immediate patch application to procmail version 3.23 or later, which contains the necessary fixes for the heap buffer overflow condition. System administrators should implement email filtering rules to detect and block potentially malicious email content that might trigger the vulnerability. Network-level protections including email gateway filtering and content inspection can provide additional layers of defense against exploitation attempts. The vulnerability aligns with CWE-122, Heap-based Buffer Overflow, and exhibits characteristics consistent with attack patterns found in the MITRE ATT&CK framework under the T1059.007 technique for Command and Scripting Interpreter. Organizations should also consider implementing memory protection mechanisms such as stack canaries, address space layout randomization, and heap integrity checking to reduce the effectiveness of potential exploitation attempts. Regular security audits and vulnerability assessments should be conducted to identify and remediate similar memory corruption vulnerabilities in other email processing components and system utilities.