CVE-2020-9760 – A buffer overflow vulnerability in WeeChat IRC ... (How to Fix)

Q: What is the severity of CVE-2020-9760?

CVE-2020-9760 has a CVSS score of 9.8 (CRITICAL). A buffer overflow vulnerability in WeeChat IRC client versions 0.3.4 through 2.7 allows remote attackers to crash the application or potentially execute arbitrary code by sending specially crafted IRC messages with long nick prefixes. This affects all users running vulnerable versions of WeeChat who connect to IRC servers.

📋 TL;DR

A buffer overflow vulnerability in WeeChat IRC client versions 0.3.4 through 2.7 allows remote attackers to crash the application or potentially execute arbitrary code by sending specially crafted IRC messages with long nick prefixes. This affects all users running vulnerable versions of WeeChat who connect to IRC servers.

💻 Affected Systems

Products:

WeeChat

Versions: 0.3.4 through 2.7

Operating Systems: Linux, macOS, BSD, Windows

Default Config Vulnerable: ⚠️ Yes

Notes: All configurations using IRC plugin are vulnerable when connecting to IRC servers.

📦 What is this software?

⚠️ Risk & Real-World Impact

🔴

Worst Case

Remote code execution leading to complete system compromise, data theft, or installation of persistent backdoors.

🟠

Likely Case

Application crash (denial of service) when processing malicious IRC messages from untrusted servers.

🟢

If Mitigated

Limited to application crash if exploit attempts fail or are blocked by network controls.

🌐 Internet-Facing: HIGH - Attackers can exploit this remotely via IRC protocol without authentication.

🏢 Internal Only: MEDIUM - Requires connection to malicious or compromised IRC servers, which could occur internally.

🎯 Exploit Status

Public PoC: ⚠️ Yes

Weaponized: LIKELY

Unauthenticated Exploit: ⚠️ Yes

Complexity: LOW

Exploitation requires sending crafted IRC 005 messages, which is straightforward for attackers controlling IRC servers.

🛠️ Fix & Mitigation

✅ Official Fix

Patch Version: 2.7.1

Vendor Advisory: https://weechat.org/doc/security/

Restart Required: Yes

Instructions:

1. Update WeeChat to version 2.7.1 or later using your package manager. 2. For Debian/Ubuntu: sudo apt update && sudo apt upgrade weechat. 3. For source installation: download from weechat.org and compile. 4. Restart WeeChat after update.

🔧 Temporary Workarounds

Disconnect from untrusted IRC servers

all

Temporarily disconnect from IRC servers until patched to prevent exploitation.

/disconnect
/quit

Use network filtering

linux

Block or filter IRC traffic from untrusted sources using firewall rules.

iptables -A INPUT -p tcp --dport 6667 -j DROP
iptables -A INPUT -p tcp --dport 6697 -j DROP

🧯 If You Can't Patch

Disable IRC plugin entirely: /plugin unload irc
Use alternative IRC client until patching is possible

🔍 How to Verify

Check if Vulnerable:

Check WeeChat version: /version. If version is between 0.3.4 and 2.7 inclusive, system is vulnerable.

Check Version:

/version

Verify Fix Applied:

Verify version is 2.7.1 or higher: /version should show 2.7.1+.

📡 Detection & Monitoring

Log Indicators:

WeeChat crash logs
Segmentation fault errors in system logs
Unexpected disconnections from IRC

Network Indicators:

Unusual IRC 005 messages with long parameters
IRC traffic from suspicious sources

SIEM Query:

source="weechat.log" AND ("segmentation fault" OR "crash" OR "buffer overflow")

📊 Metadata

CVE ID: CVE-2020-9760

CVSS v3 Score: 9.8 (CRITICAL)

CVSS Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H

CWE: CWE-120

Published: March 23, 2020

Last Updated: November 21, 2024

🔗 References

https://github.com/weechat/weechat/commit/40ccacb4330a64802b1f1e28ed9a6b6d3ca9197f Patch,Third Party Advisory
https://lists.debian.org/debian-lts-announce/2020/03/msg00031.html Mailing List,Third Party Advisory
https://lists.debian.org/debian-lts-announce/2021/09/msg00018.html Mailing List,Third Party Advisory
https://security.gentoo.org/glsa/202003-51 Third Party Advisory
https://weechat.org/doc/security/ Vendor Advisory
https://github.com/weechat/weechat/commit/40ccacb4330a64802b1f1e28ed9a6b6d3ca9197f Patch,Third Party Advisory
https://lists.debian.org/debian-lts-announce/2020/03/msg00031.html Mailing List,Third Party Advisory
https://lists.debian.org/debian-lts-announce/2021/09/msg00018.html Mailing List,Third Party Advisory
https://security.gentoo.org/glsa/202003-51 Third Party Advisory
https://weechat.org/doc/security/ Vendor Advisory

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