CVE-2026-39830
Description
A flaw was found in golang.org/x/crypto/ssh. A remote malicious SSH peer can exploit this by sending unsolicited global request responses, which fills an internal buffer and blocks the connection's read loop. This prevents the associated resources from being released, leading to a resource leak per connection. The consequence is a Denial of Service (DoS) for the affected system.
Statement
This is an Important denial of service flaw in golang.org/x/crypto/ssh. A remote, unauthenticated attacker can exploit this vulnerability by sending unsolicited global request responses to an affected SSH server, leading to resource exhaustion and a denial of service. The impact is considered Important due to the potential for unauthenticated remote disruption of services utilizing the vulnerable SSH library.
Mitigation
To mitigate this denial of service vulnerability, restrict network access to any service that utilizes the `golang.org/x/crypto/ssh` library and is exposed to untrusted networks. Implement firewall rules to allow connections only from trusted hosts or networks. This action limits the ability of malicious peers to send unsolicited global request responses. A restart of the affected service may be necessary for the new network rules to be applied effectively.
Common Vulnerability Scoring System (CVSS) Score Details
Info alert:Important note
CVSS scores for open source components depend on vendor-specific factors (e.g. version or build chain). Therefore, Red Hat's score and impact rating can be different from NVD and other vendors. Red Hat remains the authoritative CVE Naming Authority (CNA) source for its products and services (see Red Hat classifications).
CVSS v3 Score Breakdown
| Red Hat | NVD | cve.org | |
|---|---|---|---|
| Base Score | 7.5 | N/A | 7.5 |
| Attack Vector | Network | N/A | Network |
| Attack Complexity | Low | N/A | Low |
| Privileges Required | None | N/A | None |
| User Interaction | None | N/A | None |
| Scope | Unchanged | N/A | Unchanged |
| Confidentiality | None | N/A | None |
| Integrity Impact | None | N/A | None |
| Availability Impact | High | N/A | High |
Vector
Red Hat: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
cve.org: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
Understanding the Weakness (CWE)
Availability
Technical Impact: DoS: Resource Consumption (Other); DoS: Resource Consumption (Memory); DoS: Resource Consumption (CPU)
An attacker that can influence the allocation of resources that are not properly released could deplete the available resource pool and prevent all other processes from accessing the same type of resource. Frequently-affected resources include memory, CPU, disk space, power or battery, etc.
Frequently Asked Questions
Not sure what something means? Check out our Security Glossary.
Want to get errata notifications? Sign up here.
