Libssh: libssh: denial of service via unchecked proxycommand fork() failure
Summary
| CVE | CVE-2026-59845 |
|---|---|
| State | PUBLISHED |
| Assigner | redhat |
| Source Priority | CVE Program / NVD first with legacy fallback |
| Published | 2026-07-21 12:18:58 UTC |
| Updated | 2026-08-17 22:17:15 UTC |
| 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. |
Risk And Classification
Primary CVSS: v3.1 5.9 MEDIUM from [email protected]
CVSS:3.1/AV:L/AC:L/PR:L/UI:R/S:C/C:N/I:N/A:H
EPSS: 0.001070000 probability, percentile 0.013500000 (date 2026-08-18)
Problem Types: CWE-390 | CWE-390 Detection of Error Condition Without Action | CWE-390 CWE-390 Detection of Error Condition Without Action
| Version | Source | Type | Score | Severity | Vector |
|---|---|---|---|---|---|
| 3.1 | [email protected] | Primary | 5.9 | MEDIUM | CVSS:3.1/AV:L/AC:L/PR:L/UI:R/S:C/C:N/I:N/A:H |
| 3.1 | [email protected] | Secondary | 5.3 | MEDIUM | CVSS:3.1/AV:L/AC:H/PR:L/UI:R/S:C/C:N/I:N/A:H |
| 3.1 | CNA | CVSS | 5.3 | MEDIUM | CVSS:3.1/AV:L/AC:H/PR:L/UI:R/S:C/C:N/I:N/A:H |
CVSS v3.1 Breakdown
Attack Vector
LocalAttack Complexity
LowPrivileges Required
LowUser Interaction
RequiredScope
ChangedConfidentiality
NoneIntegrity
NoneAvailability
HighCVSS:3.1/AV:L/AC:L/PR:L/UI:R/S:C/C:N/I:N/A:H
NVD Known Affected Configurations (CPE 2.3)
| Type | Vendor | Product | Version | Update | Edition | Language |
|---|---|---|---|---|---|---|
| Application | Libssh | Libssh | - | All | All | All |
| Operating System | Redhat | Enterprise Linux | 10.0 | All | All | All |
| Operating System | Redhat | Enterprise Linux | 8.0 | All | All | All |
| Operating System | Redhat | Enterprise Linux | 9.0 | All | All | All |
| Application | Redhat | Hardened Images | - | All | All | All |
Vendor Declared Affected Products
| Source | Vendor | Product | Version | Platforms |
|---|---|---|---|---|
| CNA | Red Hat | Red Hat Enterprise Linux 10 | unaffected 0:0.12.0-3.el10_2 * rpm | Not specified |
| CNA | Red Hat | Red Hat Hardened Images | unaffected 0.12.1-4.hum1 * rpm | Not specified |
| CNA | Red Hat | Red Hat Enterprise Linux 8 | Not specified | Not specified |
| CNA | Red Hat | Red Hat Enterprise Linux 9 | Not specified | Not specified |
References
| Reference | Source | Link | Tags |
|---|---|---|---|
| access.redhat.com/errata/RHSA-2026:55855 | [email protected] | access.redhat.com | |
| access.redhat.com/security/cve/CVE-2026-59845 | [email protected] | access.redhat.com | Vendor Advisory |
| access.redhat.com/errata/RHSA-2026:42922 | [email protected] | access.redhat.com | Vendor Advisory |
| bugzilla.redhat.com/show_bug.cgi | [email protected] | bugzilla.redhat.com | Issue Tracking, Vendor Advisory |
| CVE Program record | CVE.ORG | www.cve.org | canonical |
| NVD vulnerability detail | NVD | nvd.nist.gov | canonical, analysis |
Vendor Comments And Credit
Discovery Credit
CNA: Red Hat would like to thank Halil Oktay (oblivionsage) for reporting this issue. (en)
Additional Advisory Data
| Source | Time | Event |
|---|---|---|
| CNA | 2026-04-29T10:03:47.442Z | Reported to Red Hat. |
| CNA | 2026-07-21T11:23:44.480Z | Made public. |
Workarounds
CNA: 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.
There are currently no legacy QID mappings associated with this CVE.