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Gitea has insecure default SSH settings

Moderate severity GitHub Reviewed Published Apr 18, 2026 in go-gitea/gitea • Updated Apr 22, 2026

Package

Codestin Search App code.gitea.io/gitea (Go)

Affected versions

< 1.25.0

Patched versions

1.25.0

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.

References

@lunny lunny published to go-gitea/gitea Apr 18, 2026
Published to the GitHub Advisory Database Apr 22, 2026
Reviewed Apr 22, 2026
Last updated Apr 22, 2026

Severity

Moderate

CVSS overall score

This score calculates overall vulnerability severity from 0 to 10 and is based on the Common Vulnerability Scoring System (CVSS).
/ 10

CVSS v4 base metrics

Exploitability Metrics
Attack Vector Network
Attack Complexity High
Attack Requirements Present
Privileges Required None
User interaction None
Vulnerable System Impact Metrics
Confidentiality Low
Integrity Low
Availability None
Subsequent System Impact Metrics
Confidentiality None
Integrity None
Availability None

CVSS v4 base metrics

Exploitability Metrics
Attack Vector: This metric reflects the context by which vulnerability exploitation is possible. This metric value (and consequently the resulting severity) will be larger the more remote (logically, and physically) an attacker can be in order to exploit the vulnerable system. The assumption is that the number of potential attackers for a vulnerability that could be exploited from across a network is larger than the number of potential attackers that could exploit a vulnerability requiring physical access to a device, and therefore warrants a greater severity.
Attack Complexity: This metric captures measurable actions that must be taken by the attacker to actively evade or circumvent existing built-in security-enhancing conditions in order to obtain a working exploit. These are conditions whose primary purpose is to increase security and/or increase exploit engineering complexity. A vulnerability exploitable without a target-specific variable has a lower complexity than a vulnerability that would require non-trivial customization. This metric is meant to capture security mechanisms utilized by the vulnerable system.
Attack Requirements: This metric captures the prerequisite deployment and execution conditions or variables of the vulnerable system that enable the attack. These differ from security-enhancing techniques/technologies (ref Attack Complexity) as the primary purpose of these conditions is not to explicitly mitigate attacks, but rather, emerge naturally as a consequence of the deployment and execution of the vulnerable system.
Privileges Required: This metric describes the level of privileges an attacker must possess prior to successfully exploiting the vulnerability. The method by which the attacker obtains privileged credentials prior to the attack (e.g., free trial accounts), is outside the scope of this metric. Generally, self-service provisioned accounts do not constitute a privilege requirement if the attacker can grant themselves privileges as part of the attack.
User interaction: This metric captures the requirement for a human user, other than the attacker, to participate in the successful compromise of the vulnerable system. This metric determines whether the vulnerability can be exploited solely at the will of the attacker, or whether a separate user (or user-initiated process) must participate in some manner.
Vulnerable System Impact Metrics
Confidentiality: This metric measures the impact to the confidentiality of the information managed by the VULNERABLE SYSTEM due to a successfully exploited vulnerability. Confidentiality refers to limiting information access and disclosure to only authorized users, as well as preventing access by, or disclosure to, unauthorized ones.
Integrity: This metric measures the impact to integrity of a successfully exploited vulnerability. Integrity refers to the trustworthiness and veracity of information. Integrity of the VULNERABLE SYSTEM is impacted when an attacker makes unauthorized modification of system data. Integrity is also impacted when a system user can repudiate critical actions taken in the context of the system (e.g. due to insufficient logging).
Availability: This metric measures the impact to the availability of the VULNERABLE SYSTEM resulting from a successfully exploited vulnerability. While the Confidentiality and Integrity impact metrics apply to the loss of confidentiality or integrity of data (e.g., information, files) used by the system, this metric refers to the loss of availability of the impacted system itself, such as a networked service (e.g., web, database, email). Since availability refers to the accessibility of information resources, attacks that consume network bandwidth, processor cycles, or disk space all impact the availability of a system.
Subsequent System Impact Metrics
Confidentiality: This metric measures the impact to the confidentiality of the information managed by the SUBSEQUENT SYSTEM due to a successfully exploited vulnerability. Confidentiality refers to limiting information access and disclosure to only authorized users, as well as preventing access by, or disclosure to, unauthorized ones.
Integrity: This metric measures the impact to integrity of a successfully exploited vulnerability. Integrity refers to the trustworthiness and veracity of information. Integrity of the SUBSEQUENT SYSTEM is impacted when an attacker makes unauthorized modification of system data. Integrity is also impacted when a system user can repudiate critical actions taken in the context of the system (e.g. due to insufficient logging).
Availability: This metric measures the impact to the availability of the SUBSEQUENT SYSTEM resulting from a successfully exploited vulnerability. While the Confidentiality and Integrity impact metrics apply to the loss of confidentiality or integrity of data (e.g., information, files) used by the system, this metric refers to the loss of availability of the impacted system itself, such as a networked service (e.g., web, database, email). Since availability refers to the accessibility of information resources, attacks that consume network bandwidth, processor cycles, or disk space all impact the availability of a system.
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

EPSS score

Weaknesses

Use of a Broken or Risky Cryptographic Algorithm

The product uses a broken or risky cryptographic algorithm or protocol. Learn more on MITRE.

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 administrator, but the default is not secure. Learn more on MITRE.

CVE ID

No known CVE

GHSA ID

GHSA-3m6q-h5gj-7mrw

Source code

Credits

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