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libgit2 fails to verify SSH keys by default

Moderate
ethomson published GHSA-8643-3wh5-rmjq Jan 20, 2023

Package

libgit2

Affected versions

< 1.4.5, 1.5.0

Patched versions

1.4.5, 1.5.1

Description

libgit2, when compiled using the optional, included libssh2 backend, fails to verify SSH keys by default.

Description

When using an SSH remote with the optional, included libssh2 backend, libgit2 does not perform certificate checking by default. Prior versions of libgit2 require the caller to set the certificate_check field of libgit2's git_remote_callbacks structure - if a certificate check callback is not set, libgit2 does not perform any certificate checking. This means that by default - without configuring a certificate check callback, clients will not perform validation on the server SSH keys and may be subject to a man-in-the-middle attack.

Beginning in libgit2 v1.4.5 and v1.5.1, libgit2 will now perform host key checking by default. Users can still override the default behavior using the certificate_check function.

The libgit2 security team would like to thank the Julia and Rust security teams for responsibly disclosing this vulnerability and assisting with fixing the vulnerability.

Users are encouraged to upgrade to v1.4.5 or v1.5.1.

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 v3 base metrics

Attack vector
Network
Attack complexity
High
Privileges required
None
User interaction
Required
Scope
Unchanged
Confidentiality
None
Integrity
High
Availability
None

CVSS v3 base metrics

Attack vector: More severe the more the remote (logically and physically) an attacker can be in order to exploit the vulnerability.
Attack complexity: More severe for the least complex attacks.
Privileges required: More severe if no privileges are required.
User interaction: More severe when no user interaction is required.
Scope: More severe when a scope change occurs, e.g. one vulnerable component impacts resources in components beyond its security scope.
Confidentiality: More severe when loss of data confidentiality is highest, measuring the level of data access available to an unauthorized user.
Integrity: More severe when loss of data integrity is the highest, measuring the consequence of data modification possible by an unauthorized user.
Availability: More severe when the loss of impacted component availability is highest.
CVSS:3.1/AV:N/AC:H/PR:N/UI:R/S:U/C:N/I:H/A:N

CVE ID

CVE-2023-22742

Weaknesses

No CWEs