GHSA-3m6q-h5gj-7mrw Gitea has insecure default SSH settings

Not scored Published 22 Apr 2026

Gitea's built-in SSH server advertises weak cryptographic algorithms by default, potentially allowing downgrade attacks or interception of SSH traffic.

Exploited in the wild: Not known
Login needed: Not needed
Attackable: Over the internet
Victim action needed: Not needed
Fix: Available

What is GHSA-3m6q-h5gj-7mrw?

GHSA-3m6q-h5gj-7mrw is a vulnerability in code.gitea.io/gitea, published on 22 Apr 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.

Official description

Summary

The built-in SSH server currently advertises a number of key exchange, MAC, and host key algorithms that are considered weak or broken. The defaults should be tightened so a fresh installation passes a baseline SSH security audit out of the box.

Details

Running ssh-audit against a default deployment flags the following as fail:

Key exchange
- ecdh-sha2-nistp256
- ecdh-sha2-nistp384
- ecdh-sha2-nistp521
MAC
- hmac-sha1
Host key
- ssh-rsa

Reproduction

docker run -it --rm positronsecurity/ssh-audit -p 2222 gitea.local

Impact

Default deployments expose algorithms that are known-weak or deprecated upstream. The current workaround requires manually setting several GITEA__server__SSH_SERVER_* variables, which most users will never do.

Workaround

[server]
SSH_SERVER_KEY_EXCHANGES = curve25519-sha256, diffie-hellman-group14-sha256
SSH_SERVER_CIPHERS       = [email protected], aes128-ctr, aes192-ctr, aes256-ctr, [email protected], [email protected]
SSH_SERVER_MACS          = [email protected], hmac-sha2-256

There is no exposed option to restrict host key algorithms, so ssh-rsa remains advertised.

Acceptance criteria

Default SSH_SERVER_KEY_EXCHANGES, SSH_SERVER_CIPHERS, and SSH_SERVER_MACS updated to the secure list above.
New SSH_SERVER_HOST_KEY_ALGORITHMS option added, with a default that excludes ssh-rsa.
Documentation updated to reflect the new defaults.
ssh-audit against a fresh install reports no [fail] entries.

Which versions are affected by GHSA-3m6q-h5gj-7mrw?

3 open source packages ship an affected version, including code.gitea.io/gitea.

Package	Affected	Fixed in
`code.gitea.io/gitea` Go	All versions	`1.25.0`
`code.gitea.io/gitea` Go	All versions	`1.25.0`
`code.gitea.io/gitea` Go	All versions	`1.25.0`

How do I fix GHSA-3m6q-h5gj-7mrw?

Upgrade code.gitea.io/gitea to 1.25.0 or later.

Is GHSA-3m6q-h5gj-7mrw being exploited?

There is no known exploitation of GHSA-3m6q-h5gj-7mrw in the wild and no public exploit code.

Sources

Also known as GO-2026-5091.