GO-2026-6303 CVE-2026-56854
Source-address critical option not enforced for non-public-key auth callbacks in golang.org/x/crypto/ssh
- Severity
- 7.5 / 10
- High · CVSS 3.1
- Exploit chance (EPSS)
- 0.44%
- Chance of exploitation in the next 30 days. Higher than 38.02% of scored vulnerabilities.
- Known exploited
- No
- Not in CISA's catalog
- Weakness
- CWE-863 Incorrect Authorization
- Fix
0.55.0- Upgrade golang.org/x/crypto to this version or later
Description
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.
Affected versions
Go
| Package | Vulnerable | Fixed in |
|---|---|---|
| golang.org/x/crypto | < 0.55.0 |
0.55.0 |
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.
golang.org/x/crypto Go → 0.55.0
- go
go get golang.org/x/crypto@v0.55.0 && go mod tidy
Severity breakdown
CVSS 3.1 7.5
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N
- Attack vector
- Network
- Attack complexity
- Low
- Privileges required
- None
- User interaction
- None
- Scope
- Unchanged
- Confidentiality
- High
- Integrity
- None
- Availability
- None
Weakness
CWE-863: Incorrect Authorization
The product performs an authorization check when an actor attempts to access a resource or perform an action, but it does not correctly perform the check.
How to prevent it
- Architecture and Design: Divide the product into anonymous, normal, privileged, and administrative areas. Reduce the attack surface by carefully mapping roles with data and functionality. Use role-based access control (RBAC) [REF-229] to enforce the roles at the appropriate boundaries. Note that this approach may not protect against horizontal authorization, i.e., it will not protect a user from attacking others with the same role.
- Architecture and Design: Ensure that access control checks are performed related to the business logic. These checks may be different than the access control checks that are applied to more generic resources such as files, connections, processes, memory, and database records. For example, a database may restrict access for medical records to a specific database user, but each record might only be intended to be accessible to the patient and the patient's doctor [REF-7].
- 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. For example, consider using authorization frameworks such as the JAAS Authorization Framework [REF-233] and the OWASP ESAPI Access Control feature [REF-45].
- Architecture and Design: For web applications, make sure that the access control mechanism is enforced correctly at the server side on every page. Users should not be able to access any unauthorized functionality or information by simply requesting direct access to that page. One way to do this is to ensure that all pages containing sensitive information are not cached, and that all such pages restrict access to requests that are accompanied by an active and authenticated session token associated with a user who has the required permissions to access that page.
- System Configuration, Installation: Use the access control capabilities of your operating system and server environment and define your access control lists accordingly. Use a "default deny" policy when defining these ACLs.
References
Fixes and patches
Issue reports
Other links
Timeline
- Published
- Last updated by the source
- Latest EPSS score
Related advisories
| Advisory | Severity | Why it's related |
|---|---|---|
| GO-2026-6355 Prevent DoS on deadlocked established channel in golang.org/x/crypto/ssh | High | Also affects golang.org/x/crypto |
| GO-2026-6354 Prevent DoS on deadlocked undecided channel in golang.org/x/crypto/ssh | High | Also affects golang.org/x/crypto |
| GO-2026-5932 The golang.org/x/crypto/openpgp package is unmaintained, unsafe by design, and has known security issues | Not rated yet | Also affects golang.org/x/crypto |
| GHSA-x527-x647-q7gg golang.org/x/crypto: Invoking VerifiedPublicKeyCallback permissions skip enforcement | Critical | Also affects golang.org/x/crypto |
| GHSA-w879-237q-wc7r golang.org/x/crypto: Invoking pathological RSA/DSA parameters may cause DoS | High | Also affects golang.org/x/crypto |
| GHSA-vgwf-h737-ff37 golang.org/x/crypto: Invoking client can cause server deadlock on unexpected responses | Critical | Also affects golang.org/x/crypto |
| GHSA-rm3j-f69w-wqmq golang.org/x/crypto vulnerable to infinite loop on large channel writes | Critical | Also affects golang.org/x/crypto |
| GHSA-qpw4-5x99-6vjp golang.org/x/crypto: Invoking memory leak when rejecting channels can lead to DoS | Medium | Also affects golang.org/x/crypto |
Credits: Longwei Wang (@gn00295120)
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