CVE-2026-39835: CWE-476: NULL Pointer Dereference in golang.org/x/crypto golang.org/x/crypto/ssh
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.
AI Analysis
Technical Summary
The vulnerability (CVE-2026-39835) affects the golang.org/x/crypto/ssh package. When an SSH server uses CertChecker as a public key callback but does not set the IsUserAuthority or IsHostAuthority callbacks, a client presenting a certificate can trigger a NULL pointer dereference, causing the server to panic. The issue arises because CertChecker previously did not handle nil callbacks gracefully. The updated behavior is to return an error instead of panicking, preventing the NULL pointer dereference.
Potential Impact
An attacker could cause the SSH server to panic, potentially leading to denial of service conditions. There is no indication of code execution or privilege escalation. No known exploits are reported in the wild.
Mitigation Recommendations
Patch status is not yet confirmed — check the vendor advisory for current remediation guidance. Users should verify if their golang.org/x/crypto/ssh version includes the fix where CertChecker returns an error instead of panicking when IsUserAuthority or IsHostAuthority are nil. Until then, avoid using CertChecker without setting these callbacks or implement additional error handling to prevent server crashes.
CVE-2026-39835: CWE-476: NULL Pointer Dereference in golang.org/x/crypto golang.org/x/crypto/ssh
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.
AI-Powered Analysis
Machine-generated threat intelligence
Technical Analysis
The vulnerability (CVE-2026-39835) affects the golang.org/x/crypto/ssh package. When an SSH server uses CertChecker as a public key callback but does not set the IsUserAuthority or IsHostAuthority callbacks, a client presenting a certificate can trigger a NULL pointer dereference, causing the server to panic. The issue arises because CertChecker previously did not handle nil callbacks gracefully. The updated behavior is to return an error instead of panicking, preventing the NULL pointer dereference.
Potential Impact
An attacker could cause the SSH server to panic, potentially leading to denial of service conditions. There is no indication of code execution or privilege escalation. No known exploits are reported in the wild.
Mitigation Recommendations
Patch status is not yet confirmed — check the vendor advisory for current remediation guidance. Users should verify if their golang.org/x/crypto/ssh version includes the fix where CertChecker returns an error instead of panicking when IsUserAuthority or IsHostAuthority are nil. Until then, avoid using CertChecker without setting these callbacks or implement additional error handling to prevent server crashes.
Technical Details
- Data Version
- 5.2
- Assigner Short Name
- Go
- Date Reserved
- 2026-04-07T18:13:03.529Z
- Cvss Version
- null
- State
- PUBLISHED
- Remediation Level
- null
Threat ID: 6a0fcdabe1370fbb487d5029
Added to database: 5/22/2026, 3:29:47 AM
Last enriched: 5/22/2026, 3:45:03 AM
Last updated: 5/22/2026, 5:21:13 PM
Views: 7
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