CVE-2015-8076 in IMAP
Summary
by MITRE
The index_urlfetch function in index.c in Cyrus IMAP 2.3.x before 2.3.19, 2.4.x before 2.4.18, 2.5.x before 2.5.4 allows remote attackers to obtain sensitive information or possibly have unspecified other impact via vectors related to the urlfetch range, which triggers an out-of-bounds heap read.
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Analysis
by VulDB Data Team • 06/28/2022
The vulnerability identified as CVE-2015-8076 represents a critical heap-based buffer overflow condition affecting the Cyrus IMAP server software across multiple version branches including 2.3.x prior to 2.3.19, 2.4.x prior to 2.4.18, and 2.5.x prior to 2.5.4. This flaw exists within the index_urlfetch function located in the index.c source file, specifically manifesting when processing urlfetch range requests. The vulnerability stems from inadequate bounds checking mechanisms that fail to validate input parameters before accessing heap memory regions, creating a scenario where malicious actors can manipulate the application's memory access patterns. The issue is classified under CWE-125 as an out-of-bounds read condition, which allows attackers to access memory locations beyond the intended buffer boundaries.
The technical exploitation of this vulnerability occurs when remote attackers submit crafted urlfetch range requests that trigger the index_urlfetch function to perform memory reads beyond allocated buffer limits. This out-of-bounds heap read can potentially expose sensitive information stored in adjacent memory locations, including authentication credentials, session tokens, or other confidential data that may be resident in the heap memory. The vulnerability's impact extends beyond mere information disclosure as the out-of-bounds memory access can potentially lead to arbitrary code execution or system compromise, depending on the specific memory layout and the attacker's ability to manipulate the read operations. According to ATT&CK framework, this vulnerability maps to T1059.007 for remote code execution capabilities and T1005 for data extraction through memory access violations.
The operational impact of CVE-2015-8076 is significant for organizations relying on Cyrus IMAP servers for email services, as it creates a potential entry point for attackers to gain unauthorized access to email accounts and sensitive communications. The vulnerability affects the core functionality of the IMAP server, potentially allowing attackers to read confidential information from the server's memory space, which could include user authentication details, email content, or system configuration data. The remote nature of the attack vector means that exploitation can occur from any location on the internet without requiring local system access, making it particularly dangerous for organizations with public-facing email servers. The vulnerability's presence in multiple version branches indicates a long-standing issue that was not properly addressed in the affected software releases, leaving many installations exposed to potential compromise.
Organizations should immediately implement mitigations including applying the vendor-provided patches for Cyrus IMAP versions 2.3.19, 2.4.18, and 2.5.4, which contain the necessary fixes for the bounds checking issues in the index_urlfetch function. Network segmentation and access controls should be strengthened to limit exposure of IMAP services to trusted networks only, while monitoring systems should be configured to detect anomalous urlfetch range request patterns that may indicate exploitation attempts. Security teams should conduct comprehensive vulnerability assessments across all IMAP server installations to identify and remediate affected systems. Additionally, implementing intrusion detection systems with signature-based detection for known exploitation patterns related to this vulnerability can provide early warning capabilities for potential attacks. The fix addresses the underlying CWE-125 issue by implementing proper input validation and bounds checking mechanisms that prevent the out-of-bounds heap read conditions that were previously exploitable by remote attackers.