CVE-2026-59845
Description
A flaw was found in libssh. When ProxyCommand is used, an unchecked fork() failure can be stored as process ID -1; during cleanup, signals may then be sent across the caller's accessible process tree, leading to local denial of service.
Statement
This Moderate flaw in libssh client-side ProxyCommand handling can lead to a local denial of service. When ProxyCommand is configured, an unchecked fork() failure may result in signals being sent across the process tree, disrupting local system availability. This issue specifically impacts environments utilizing ProxyCommand functionality.
Mitigation
To mitigate this issue, avoid using the ProxyCommand feature in libssh client configurations. This prevents the vulnerable code path from being exercised, thereby eliminating the risk of local denial of service due to unchecked fork() failures.
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 | 5.3 | 5.9 | 5.3 |
| Attack Vector | Local | Local | Local |
| Attack Complexity | High | Low | High |
| Privileges Required | Low | Low | Low |
| User Interaction | Required | Required | Required |
| Scope | Changed | Changed | Changed |
| Confidentiality | None | None | None |
| Integrity Impact | None | None | None |
| Availability Impact | High | High | High |
Vector
Red Hat: CVSS:3.1/AV:L/AC:H/PR:L/UI:R/S:C/C:N/I:N/A:H
NVD: CVSS:3.1/AV:L/AC:L/PR:L/UI:R/S:C/C:N/I:N/A:H
cve.org: CVSS:3.1/AV:L/AC:H/PR:L/UI:R/S:C/C:N/I:N/A:H
Understanding the Weakness (CWE)
Integrity,Other
Technical Impact: Varies by Context; Unexpected State; Alter Execution Logic
An attacker could utilize an ignored error condition to place the system in an unexpected state that could lead to the execution of unintended logic and could cause other unintended behavior.
Acknowledgements
Red Hat would like to thank Halil Oktay (oblivionsage) for reporting this issue.
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