{"id":"GHSA-3m6q-h5gj-7mrw","aliases":["GO-2026-5091"],"status":"published","title":"Gitea has insecure default SSH settings","description":"## Summary\n\nThe 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.\n\n## Details\n\nRunning `ssh-audit` against a default deployment flags the following as `fail`:\n\n- **Key exchange**\n  - `ecdh-sha2-nistp256`\n  - `ecdh-sha2-nistp384`\n  - `ecdh-sha2-nistp521`\n- **MAC**\n  - `hmac-sha1`\n- **Host key**\n  - `ssh-rsa`\n\n## Reproduction\n\n```sh\ndocker run -it --rm positronsecurity/ssh-audit -p 2222 gitea.local\n```\n\n## Impact\n\nDefault 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.\n\n### Workaround\n\n```ini\n[server]\nSSH_SERVER_KEY_EXCHANGES = curve25519-sha256, diffie-hellman-group14-sha256\nSSH_SERVER_CIPHERS       = chacha20-poly1305@openssh.com, aes128-ctr, aes192-ctr, aes256-ctr, aes128-gcm@openssh.com, aes256-gcm@openssh.com\nSSH_SERVER_MACS          = hmac-sha2-256-etm@openssh.com, hmac-sha2-256\n```\n\nThere is no exposed option to restrict host key algorithms, so `ssh-rsa` remains advertised.\n\n## Acceptance criteria\n\n- [ ] Default `SSH_SERVER_KEY_EXCHANGES`, `SSH_SERVER_CIPHERS`, and `SSH_SERVER_MACS` updated to the secure list above.\n- [ ] New `SSH_SERVER_HOST_KEY_ALGORITHMS` option added, with a default that excludes `ssh-rsa`.\n- [ ] Documentation updated to reflect the new defaults.\n- [ ] `ssh-audit` against a fresh install reports no `[fail]` entries.","severity":{"version":"4.0","score":6.3,"vector":"CVSS:4.0/AV:N/AC:H/AT:P/PR:N/UI:N/VC:L/VI:L/VA:N/SC:N/SI:N/SA:N","level":"medium","from":"ghsa"},"facts":{"in_kev":false,"known_exploited":false,"public_exploit":false,"fix_available":true},"cwes":["CWE-1188","CWE-327"],"published":"2026-04-22T20:37:21Z","modified":"2026-06-25T18:56:39Z","fixes":[{"ecosystem":"Go","package":"code.gitea.io/gitea","fixed_in":["1.25.0"],"sources":["ghsa","osv"]}],"affected":[{"source":"ghsa","ecosystem":"Go","package":"code.gitea.io/gitea","ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"fixed":"1.25.0"}]}]},{"source":"osv","ecosystem":"Go","package":"code.gitea.io/gitea","ranges":[{"type":"SEMVER","events":[{"introduced":"0"},{"fixed":"1.25.0"}]}]},{"source":"osv","ecosystem":"Go","package":"code.gitea.io/gitea","ranges":[{"type":"SEMVER","events":[{"introduced":"0"},{"fixed":"1.25.0"}]}]}],"references":[{"url":"https://github.com/go-gitea/gitea/security/advisories/GHSA-3m6q-h5gj-7mrw","tags":["web","advisory"]},{"url":"https://github.com/advisories/GHSA-3m6q-h5gj-7mrw"},{"url":"https://github.com/go-gitea/gitea","tags":["package"]}],"sources":{"ghsa":[{"id":"GHSA-3m6q-h5gj-7mrw","title":"Gitea has insecure default SSH settings","description":"## Summary\n\nThe 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.\n\n## Details\n\nRunning `ssh-audit` against a default deployment flags the following as `fail`:\n\n- **Key exchange**\n  - `ecdh-sha2-nistp256`\n  - `ecdh-sha2-nistp384`\n  - `ecdh-sha2-nistp521`\n- **MAC**\n  - `hmac-sha1`\n- **Host key**\n  - `ssh-rsa`\n\n## Reproduction\n\n```sh\ndocker run -it --rm positronsecurity/ssh-audit -p 2222 gitea.local\n```\n\n## Impact\n\nDefault 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.\n\n### Workaround\n\n```ini\n[server]\nSSH_SERVER_KEY_EXCHANGES = curve25519-sha256, diffie-hellman-group14-sha256\nSSH_SERVER_CIPHERS       = chacha20-poly1305@openssh.com, aes128-ctr, aes192-ctr, aes256-ctr, aes128-gcm@openssh.com, aes256-gcm@openssh.com\nSSH_SERVER_MACS          = hmac-sha2-256-etm@openssh.com, hmac-sha2-256\n```\n\nThere is no exposed option to restrict host key algorithms, so `ssh-rsa` remains advertised.\n\n## Acceptance criteria\n\n- [ ] Default `SSH_SERVER_KEY_EXCHANGES`, `SSH_SERVER_CIPHERS`, and `SSH_SERVER_MACS` updated to the secure list above.\n- [ ] New `SSH_SERVER_HOST_KEY_ALGORITHMS` option added, with a default that excludes `ssh-rsa`.\n- [ ] Documentation updated to reflect the new defaults.\n- [ ] `ssh-audit` against a fresh install reports no `[fail]` entries.","status":"published","published":"2026-04-22T20:37:21Z","modified":"2026-04-22T20:37:22Z","cvss":[{"version":"4.0","score":6.3,"vector":"CVSS:4.0/AV:N/AC:H/AT:P/PR:N/UI:N/VC:L/VI:L/VA:N/SC:N/SI:N/SA:N","level":"medium"}],"cwes":["CWE-327","CWE-1188"],"updated_at":"2026-11-02T14:39:56.453138Z"}],"osv":[{"id":"GHSA-3m6q-h5gj-7mrw","title":"Gitea has insecure default SSH settings","description":"## Summary\n\nThe 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.\n\n## Details\n\nRunning `ssh-audit` against a default deployment flags the following as `fail`:\n\n- **Key exchange**\n  - `ecdh-sha2-nistp256`\n  - `ecdh-sha2-nistp384`\n  - `ecdh-sha2-nistp521`\n- **MAC**\n  - `hmac-sha1`\n- **Host key**\n  - `ssh-rsa`\n\n## Reproduction\n\n```sh\ndocker run -it --rm positronsecurity/ssh-audit -p 2222 gitea.local\n```\n\n## Impact\n\nDefault 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.\n\n### Workaround\n\n```ini\n[server]\nSSH_SERVER_KEY_EXCHANGES = curve25519-sha256, diffie-hellman-group14-sha256\nSSH_SERVER_CIPHERS       = chacha20-poly1305@openssh.com, aes128-ctr, aes192-ctr, aes256-ctr, aes128-gcm@openssh.com, aes256-gcm@openssh.com\nSSH_SERVER_MACS          = hmac-sha2-256-etm@openssh.com, hmac-sha2-256\n```\n\nThere is no exposed option to restrict host key algorithms, so `ssh-rsa` remains advertised.\n\n## Acceptance criteria\n\n- [ ] Default `SSH_SERVER_KEY_EXCHANGES`, `SSH_SERVER_CIPHERS`, and `SSH_SERVER_MACS` updated to the secure list above.\n- [ ] New `SSH_SERVER_HOST_KEY_ALGORITHMS` option added, with a default that excludes `ssh-rsa`.\n- [ ] Documentation updated to reflect the new defaults.\n- [ ] `ssh-audit` against a fresh install reports no `[fail]` entries.","status":"published","published":"2026-04-22T20:37:21Z","modified":"2026-06-25T18:56:39.025404508Z","cvss":[{"version":"4.0","score":6.3,"vector":"CVSS:4.0/AV:N/AC:H/AT:P/PR:N/UI:N/VC:L/VI:L/VA:N/SC:N/SI:N/SA:N","level":"medium"}],"cwes":["CWE-1188","CWE-327"],"updated_at":"2026-11-02T15:46:35.747385Z"},{"id":"GO-2026-5091","title":"Gitea has insecure default SSH settings in code.gitea.io/gitea","description":"Gitea has insecure default SSH settings in code.gitea.io/gitea","status":"published","published":"2026-06-25T18:26:48Z","modified":"2026-06-25T18:45:20.876508182Z","updated_at":"2026-11-02T15:47:02.280725Z"}]}}