CVE-2020-8955
📋 TL;DR
CVE-2020-8955 is a buffer overflow vulnerability in WeeChat's IRC plugin that allows remote attackers to crash the application or potentially execute arbitrary code by sending a specially crafted IRC 324 (channel mode) message. This affects all WeeChat users connecting to IRC servers, particularly those who join channels where attackers can send malicious messages.
💻 Affected Systems
- WeeChat
📦 What is this software?
Backports Sle by Opensuse
Backports Sle by Opensuse
Fedora by Fedoraproject
Fedora by Fedoraproject
Fedora by Fedoraproject
Leap by Opensuse
Weechat by Weechat
⚠️ Risk & Real-World Impact
Worst Case
Remote code execution leading to complete system compromise of the WeeChat user's machine.
Likely Case
Denial of service through application crash, potentially with memory corruption that could lead to information disclosure.
If Mitigated
Application crash only, with no privilege escalation if running with limited permissions.
🎯 Exploit Status
Exploit requires ability to send IRC 324 messages to target channels. Public proof-of-concept demonstrates crash.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: WeeChat 2.8 and later
Vendor Advisory: https://github.com/weechat/weechat/commit/6f4f147d8e86adf9ad34a8ffd7e7f1f23a7e74da
Restart Required: Yes
Instructions:
1. Update WeeChat to version 2.8 or later using your package manager. 2. For source installation: git clone, checkout latest release, compile and install. 3. Restart WeeChat after update.
🔧 Temporary Workarounds
Disable IRC plugin
allTemporarily disable the vulnerable IRC plugin until patching is possible.
/plugin unload irc
Use IRC bouncer
allConnect to IRC through a separate bouncer service that filters malicious messages.
🧯 If You Can't Patch
- Run WeeChat with reduced privileges (non-root user, containerization)
- Implement network segmentation to restrict IRC traffic to trusted servers only
🔍 How to Verify
Check if Vulnerable:
Check WeeChat version: if version ≤ 2.7 and IRC plugin is loaded, system is vulnerable.Check Version:
/versionVerify Fix Applied:
Verify WeeChat version is ≥ 2.8 and check that the fix commit 6f4f147d is included.📡 Detection & Monitoring
Log Indicators:
- WeeChat crash logs
- Segmentation fault errors in system logs
- Abnormal IRC 324 message patterns
Network Indicators:
- IRC 324 messages with unusually long mode strings
- IRC traffic from unexpected sources
SIEM Query:
source="*weechat*" AND ("segmentation fault" OR "buffer overflow" OR "irc_mode_channel_update")🔗 References
- http://lists.opensuse.org/opensuse-security-announce/2020-02/msg00032.html
- https://github.com/weechat/weechat/commit/6f4f147d8e86adf9ad34a8ffd7e7f1f23a7e74da
- https://lists.debian.org/debian-lts-announce/2020/03/msg00031.html
- https://lists.debian.org/debian-lts-announce/2021/09/msg00018.html
- https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/4ASRTCQFFDAAK347URWNDH6NSED2BGNY/
- https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/ER23GT23US5JXDLUZAMGMWXKZ74MI4S2/
- https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/M3LAJTLI3LWZRNCFYJ7PCBBTHUMCCBHH/
- https://security.gentoo.org/glsa/202003-51
- https://weechat.org/doc/security/
- http://lists.opensuse.org/opensuse-security-announce/2020-02/msg00032.html
- https://github.com/weechat/weechat/commit/6f4f147d8e86adf9ad34a8ffd7e7f1f23a7e74da
- https://lists.debian.org/debian-lts-announce/2020/03/msg00031.html
- https://lists.debian.org/debian-lts-announce/2021/09/msg00018.html
- https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/4ASRTCQFFDAAK347URWNDH6NSED2BGNY/
- https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/ER23GT23US5JXDLUZAMGMWXKZ74MI4S2/
- https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/M3LAJTLI3LWZRNCFYJ7PCBBTHUMCCBHH/
- https://security.gentoo.org/glsa/202003-51
- https://weechat.org/doc/security/
