When receiving a DCC file, the filename built contains the remote nick (the option xfer.file.use_nick_in_filename is on by default).
If the nick contains special characters, the file could be written outside of the configured download path.
Xfer never overwrites existing files, so if a file exists with the same name, a suffix like ".1" is appended to the filename.
Mitigation
Turn off option to include nick in filename: /set xfer.file.use_nick_in_filename off.
Credit
The issue was discovered by aizu-m.
WSA-2026-4: [Relay] Missing size limit for the received websocket frame, HTTP message and HTTP body.
When receiving part of websocket frame, HTTP message or HTTP body, the Relay plugin builds a partial buffer until the end of data is found.
There is no limit for the allocated buffer.
A malicious client sending large amount of data without end of websocket frame or HTTP message/body can lead to memory exhaustion and the WeeChat process can be killed by the OOM killer.
Mitigation
There are multiple ways to mitigate this issue:
Remove all relays, see: /help relay
Unload relay plugin with command: /plugin unload relay and see: /help weechat.plugin.autoload
Secure relay to allow only trusted IP addresses, see: /help relay.network.allowed_ips
WSA-2026-3: [IRC] Missing size limit for the unterminated IRC message or isupport value (message 005).
When receiving data on the socket, the IRC plugin builds a partial message until "\r\n" is found.
There is no limit for the allocated message.
A malicious server sending large amount of data without end of message ("\r\n") can lead to memory exhaustion and the WeeChat process can be killed by the OOM killer.
Mitigation
There is no known mitigation.
The upgrade to the latest stable version is highly recommended.
WSA-2026-2: [API, Relay] Non-constant time password/hash comparison.
WeeChat uses non-constant time password/hash comparison in the Relay plugin and in TOTP validation.
This could allow an attacker to guess a password, a hash or a TOTP and bypass relay authentication.
Mitigation
There are multiple ways to mitigate this issue:
Remove all relays, see: /help relay
Unload relay plugin with command: /plugin unload relay and see: /help weechat.plugin.autoload
Secure relay to allow some trusted IP addresses, see: /help relay.network.allowed_ips
Credit
The issue was discovered by Tristan Madani (@TristanInSec) from Talence Security.
WSA-2025-7: [Core] Buffer overflow in range of chars in evaluated expressions.
Integer overflow happens in conversion of a version as string to an integer number, if the version is greater than 0x7FFFFFFF (127.255.255.255), so if the version is at least 0x80000000 (128.0.0.0).
Mitigation
There is no known mitigation.
The upgrade to the latest stable version is highly recommended.
WSA-2025-2: [Core] Integer overflow in base32 decode/encode functions.
An integer overflow can happen when looping over items in a list.
This can only happen in rare conditions on 32 and 64-bit systems, as the list must contain more than 2,147,483,647 elements.
On 16-bit systems, this happens with a list that contains more than 32,767 elements.
Mitigation
There is no known mitigation.
The upgrade to the latest stable version is highly recommended.