CVE-2020-8955 in WeeChat
Summary
by MITRE
irc_mode_channel_update in plugins/irc/irc-mode.c in WeeChat through 2.7 allows remote attackers to cause a denial of service (buffer overflow and application crash) or possibly have unspecified other impact via a malformed IRC message 324 (channel mode).
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Analysis
by VulDB Data Team • 03/31/2024
The vulnerability identified as CVE-2020-8955 represents a critical buffer overflow flaw within the WeeChat IRC client software, specifically affecting versions through 2.7. This issue resides in the irc_mode_channel_update function located in the plugins/irc/irc-mode.c file, which processes IRC protocol messages related to channel mode updates. The vulnerability manifests when the application receives a malformed IRC message 324, which is the standard message type used to convey channel mode information in the IRC protocol. This particular message type is essential for managing channel permissions, user privileges, and channel settings, making it a frequent and critical component of IRC communication.
The technical implementation of this vulnerability stems from inadequate input validation and bounds checking within the irc_mode_channel_update function. When WeeChat processes a malformed message 324, the application fails to properly validate the length and structure of the mode string contained within the message. This deficiency allows attackers to craft specially constructed channel mode messages that exceed the allocated buffer space, resulting in a classic buffer overflow condition. The overflow occurs because the software does not perform sufficient bounds checking before copying data into fixed-size buffers, directly violating fundamental secure coding practices and common security guidelines.
The operational impact of this vulnerability extends beyond simple denial of service, though that remains the primary concern. Remote attackers can exploit this weakness to crash the WeeChat application completely, rendering the IRC client unusable for all users connected to the affected instance. This denial of service condition can be particularly damaging in collaborative environments where multiple users rely on a single WeeChat instance for communication. Additionally, the vulnerability may potentially enable more severe consequences including arbitrary code execution, depending on the specific memory corruption patterns and the target system's memory layout. The buffer overflow could allow attackers to manipulate program execution flow, potentially leading to privilege escalation or complete system compromise, especially when the application runs with elevated privileges.
Mitigation strategies for CVE-2020-8955 should focus on immediate patch application, as the vulnerability affects multiple versions of WeeChat and represents a known security flaw that has been addressed in subsequent releases. Organizations should prioritize updating their WeeChat installations to versions 2.8 or later, where the buffer overflow has been corrected through proper input validation and bounds checking mechanisms. System administrators should also implement network-level monitoring to detect and block malformed IRC messages, particularly those with suspiciously long mode strings or unusual parameter combinations. The vulnerability aligns with CWE-121, which describes stack-based buffer overflow conditions, and may also relate to CWE-787, representing out-of-bounds write conditions. From an ATT&CK framework perspective, this vulnerability maps to T1499.004, which covers network denial of service, and potentially T1059.001 for command and scripting interpreter execution if the buffer overflow leads to code execution scenarios.