GHSA-3m6q-h5gj-7mrw GO-2026-5091

Gitea has insecure default SSH settings

Medium Go

Severity: 0.0 / 10; Medium · CVSS 4.0
Exploit chance (EPSS): —; No score published
Known exploited: No; Not in CISA's catalog
Weakness: CWE-1188 Initialization of a Resource with an Insecure Default; CWE-327 Use of a Broken or Risky Cryptographic Algorithm
Fix: 1.25.0; Upgrade code.gitea.io/gitea to this version or later

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       = chacha20-poly1305@openssh.com, aes128-ctr, aes192-ctr, aes256-ctr, aes128-gcm@openssh.com, aes256-gcm@openssh.com
SSH_SERVER_MACS          = hmac-sha2-256-etm@openssh.com, 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.

Affected versions

Go

Package	Vulnerable	Fixed in
code.gitea.io/gitea	`< 1.25.0`	`1.25.0`

How to fix

Move to the fixed version or later with your package manager, update the lockfile, and run your tests. If the package only arrives through another dependency, upgrade that dependency first. If none of its releases pulls a fixed version yet, force the version with your package manager's override.

code.gitea.io/gitea Go → `1.25.0`

go

go get code.gitea.io/gitea@v1.25.0 && go mod tidy

Severity breakdown

CVSS 4.0 0.0

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

Attack vector: Network
Attack complexity: High
Attack requirements: Present
Privileges required: None
User interaction: None
Confidentiality (vulnerable system): Low
Integrity (vulnerable system): Low
Availability (vulnerable system): None
Confidentiality (subsequent systems): None
Integrity (subsequent systems): None
Availability (subsequent systems): None

Weakness

CWE-1188: Initialization of a Resource with an Insecure Default

The product initializes or sets a resource with a default that is intended to be changed by the product's installer, administrator, or maintainer, but the default is not secure.

CWE-327: Use of a Broken or Risky Cryptographic Algorithm

The product uses a broken or risky cryptographic algorithm or protocol.

How to prevent it

Architecture and Design: When there is a need to store or transmit sensitive data, use strong, up-to-date cryptographic algorithms to encrypt that data. Select a well-vetted algorithm that is currently considered to be strong by experts in the field, and use well-tested implementations. As with all cryptographic mechanisms, the source code should be available for analysis. For example, US government systems require FIPS 140-2 certification [REF-1192]. Do not develop custom or private cryptographic algorithms. They will likely be exposed to attacks that are well-understood by cryptographers. Reverse engineering techniques are mature. If the algorithm can be compromised if attackers find out how it works, then it is especially weak. Periodically ensure that the cryptography has not become obsolete. Some older algorithms, once thought to require a billion years of computing time, can now be broken in days or hours. This includes MD4, MD5, SHA1, DES, and other algorithms that were once regarded as strong. [REF-267]
Architecture and Design: Ensure that the design allows one cryptographic algorithm to be replaced with another in the next generation or version. Where possible, use wrappers to make the interfaces uniform. This will make it easier to upgrade to stronger algorithms. With hardware, design the product at the Intellectual Property (IP) level so that one cryptographic algorithm can be replaced with another in the next generation of the hardware product.
Architecture and Design: Carefully manage and protect cryptographic keys (see CWE-320). If the keys can be guessed or stolen, then the strength of the cryptography itself is irrelevant.
Architecture and Design: Use a vetted library or framework that does not allow this weakness to occur or provides constructs that make this weakness easier to avoid [REF-1482]. Industry-standard implementations will save development time and may be more likely to avoid errors that can occur during implementation of cryptographic algorithms. Consider the ESAPI Encryption feature.
Implementation, Architecture and Design: When using industry-approved techniques, use them correctly. Don't cut corners by skipping resource-intensive steps (CWE-325). These steps are often essential for preventing common attacks.

References

Packages

github.com/go-gitea/gitea

Timeline

Apr 22, 2026 Published
Jun 25, 2026 Last updated by the source

Advisory	Severity	Why it's related
GHSA-rcr6-4jqh-j84m Gitea: Remote Code Execution via diffpatch Git Hook Installation	Critical Known exploited	Also affects code.gitea.io/gitea
GHSA-fq2p-5p22-8g6j Gitea: Public-Only Personal access tokens scope bypass in Organization and Permission Endpoints	Medium	Also affects code.gitea.io/gitea
GHSA-2wm4-vwp6-v7xc Gitea: SSRF via Migration Asset Downloads Bypasses hostmatcher — Reads Internal Files and Cloud Metadata	High	Also affects code.gitea.io/gitea
GHSA-3r5c-2xxx-h872 Gitea: Webhook Authorization Header Returned in Plaintext via API	Low	Also affects code.gitea.io/gitea
GHSA-frpw-3h2q-4jj6 Gitea: Cross-Repo Information Disclosure via Org-Level Actions Run/Job APIs	Medium	Also affects code.gitea.io/gitea
GHSA-q423-49rw-g9mh Gitea: GHSA-8fwc-qjw5-rvgp ClearRepoWatches fix not applied to API EditRepo path — sister code path retains stale watches on public->private	Medium	Also affects code.gitea.io/gitea
GHSA-2fcr-jfvc-vgg2 Gitea: Two SSRF findings	High	Also affects code.gitea.io/gitea
GHSA-fw57-jgch-pgf3 Gitea: ParseAcceptLanguage quadratic-time DoS via Locale middleware on unauthenticated requests	High	Also affects code.gitea.io/gitea

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