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GHSA-78mq-xcr3-xm33 CVE-2026-39835 GO-2026-5015

golang.org/x/crypto is vulnerable to invoking server panic during CheckHostKey/Authenticate flow

Medium Go
Severity
5.3 / 10
Medium · CVSS 3.1
Exploit chance (EPSS)
0.50%
Chance of exploitation in the next 30 days. Higher than 43.09% of scored vulnerabilities.
Known exploited
No
Not in CISA's catalog
Weakness
CWE-295 Improper Certificate Validation
CWE-476 NULL Pointer Dereference
Fix
0.52.0
Upgrade golang.org/x/crypto to this version or later

Description

SSH servers which use CertChecker as a public key callback without setting IsUserAuthority or IsHostAuthority could be caused to panic by a client presenting a certificate. CertChecker now returns an error instead of panicking when these callbacks are nil.

Affected versions

Go

PackageVulnerableFixed in
golang.org/x/crypto
< 0.52.0
0.52.0
golang.org/x/crypto
< 0.52.0
0.52.0

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 → 0.52.0

go
go get golang.org/x/crypto@v0.52.0 && go mod tidy

Severity breakdown

CVSS 3.1 5.3

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L

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

Weakness

CWE-295: Improper Certificate Validation

The product does not validate, or incorrectly validates, a certificate.

How to prevent it
  • Architecture and Design, Implementation: Certificates should be carefully managed and checked to assure that data are encrypted with the intended owner's public key.
  • Implementation: If certificate pinning is being used, ensure that all relevant properties of the certificate are fully validated before the certificate is pinned, including the hostname.

CWE-476: NULL Pointer Dereference

The product dereferences a pointer that it expects to be valid but is NULL.

How to prevent it
  • Implementation: For any pointers that could have been modified or provided from a function that can return NULL, check the pointer for NULL before use. When working with a multithreaded or otherwise asynchronous environment, ensure that proper locking APIs are used to lock before the check, and unlock when it has finished [REF-1484].
  • Requirements: Select a programming language that is not susceptible to these issues.
  • Implementation: Check the results of all functions that return a value and verify that the value is non-null before acting upon it.
  • Architecture and Design: Identify all variables and data stores that receive information from external sources, and apply input validation to make sure that they are only initialized to expected values.
  • Implementation: Explicitly initialize all variables and other data stores, either during declaration or just before the first usage.

References

Advisories

Packages

Other links

Timeline

  1. Published
  2. Last updated by the source
  3. Latest EPSS score
AdvisorySeverityWhy 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-2026-6303
Source-address critical option not enforced for non-public-key auth callbacks 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

Credits: NCC Group Cryptography Services, sponsored by Teleport

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