EUVD-2026-67741
GHSA-gjhq-gjfw-99mq
Severity by source
AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N
AC:H because exploitation requires server-side source-address restrictions configured via affected callbacks, a condition beyond attacker control; I:L added for SSH session file-transfer capability.
Primary rating from Vendor (Go).
CVSS VectorVendor: Go
Lifecycle Timeline
5DescriptionCVE.org
The source-address critical option in the Permissions returned by an authentication callback was only enforced for the PublicKeyCallback and VerifiedPublicKeyCallback paths, extending the fix for CVE-2026-46595. Permissions returned by the PasswordCallback, KeyboardInteractiveCallback, NoClientAuthCallback, and GSSAPIWithMICConfig.AllowLogin callbacks were not validated against the client's remote address, so a source-address restriction set by those callbacks was silently ignored. The check is now applied to the Permissions returned by any authentication callback.
AnalysisAI
Source-address critical option enforcement in golang.org/x/crypto/ssh is incomplete, allowing remote attackers to bypass IP-based access controls on Go-based SSH servers using PasswordCallback, KeyboardInteractiveCallback, NoClientAuthCallback, or GSSAPIWithMICConfig.AllowLogin authentication paths. Versions prior to 0.55.0 silently ignore source-address restrictions returned by these callbacks, defeating an explicit authorization control set by the server application. …
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Attack ChainAIDerived
Hypothetical attack flow derived from CVE metadata
Vulnerability AssessmentAI
| Exploitation | Exploitation requires three co-occurring conditions: (1) the target application implements an SSH server using golang.org/x/crypto/ssh at a version prior to 0.55.0; (2) the application uses at least one of PasswordCallback, KeyboardInteractiveCallback, NoClientAuthCallback, or GSSAPIWithMICConfig.AllowLogin as its authentication mechanism; and (3) the Permissions object returned by that callback includes a source-address critical option restricting client IP addresses. … Additional conditions and limiting factors are described in the full assessment. |
| Risk Assessment | The NVD-assigned CVSS 3.1 vector (AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N, 7.5 High) reflects network-reachable, unauthenticated exploitation with high confidentiality impact and no user interaction. … Full risk analysis with EPSS, KEV, and SSVC signal comparison available after sign-in. |
| Exploit Scenario | Full exploit scenario with step-by-step reproduction available after sign-in. |
| Remediation | Upgrade golang.org/x/crypto to version 0.55.0 or later, which unifies source-address critical option enforcement across all authentication callback paths. … Detailed patch versions, workarounds, and compensating controls in full report. |
Recommended ActionAI
Within 24 hours, identify all Go applications using golang.org/x/crypto/ssh and determine which ones enforce IP-based source-address restrictions. …
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Same weakness CWE-863 – Incorrect Authorization
View allSame technique Authentication Bypass
View allVendor StatusVendor
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