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OpenSSH CVE-2026-59997

| EUVDEUVD-2026-42139 MEDIUM
Improper Validation of Specified Quantity in Input (CWE-1284)
2026-07-08 mitre GHSA-56r6-6mmg-25j5
5.4
CVSS 3.1 · NVD
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Severity by source

Vendor (mitre) PRIMARY
MEDIUM
qualitative
NVD
5.4 MEDIUM
AV:N/AC:L/PR:N/UI:R/S:U/C:L/I:L/A:N
vuln.today AI
4.2 MEDIUM

SFTP always requires authentication so PR:L is accurate; specific >9-argument config is required (AC:H); no user interaction beyond normal SFTP connection.

3.1 AV:N/AC:H/PR:L/UI:N/S:U/C:L/I:L/A:N
4.0 AV:N/AC:H/AT:P/PR:L/UI:N/VC:L/VI:L/VA:N/SC:N/SI:N/SA:N
SUSE
4.2 MEDIUM
AV:N/AC:H/PR:N/UI:R/S:U/C:L/I:L/A:N
Red Hat
5.4 MEDIUM
qualitative

Primary rating from Vendor (mitre).

CVSS VectorNVD

Attack Vector
Network
Attack Complexity
Low
Privileges Required
None
User Interaction
Required
Scope
Unchanged
Confidentiality
Low
Integrity
Low
Availability
None

Lifecycle Timeline

3
CVSS changed
Jul 09, 2026 - 17:22 NVD
4.2 (MEDIUM) 5.4 (MEDIUM)
Patch available
Jul 08, 2026 - 02:01 EUVD
Analysis Generated
Jul 08, 2026 - 01:29 vuln.today

DescriptionNVD

internal-sftp in sshd in OpenSSH before 10.4 recognizes only the first 9 command-line arguments, which can be important if a later command-line argument would have helped to ensure the intended security properties of an SFTP connection.

AnalysisAI

OpenSSH's internal-sftp subsystem silently discards all command-line arguments beyond position 9, allowing authenticated SFTP users to bypass security restrictions that administrators intended to enforce via those later-positioned arguments. All OpenSSH releases before 10.4 are affected when sshd_config supplies more than nine arguments to the internal-sftp subsystem, which is a non-default but legitimate administrative pattern used for directory restriction, read-only enforcement, and umask control. No public exploit has been identified and this vulnerability is not listed in the CISA KEV catalog; however, sites relying on complex internal-sftp argument chains for access policy enforcement face a direct, silent policy bypass.

Technical ContextAI

internal-sftp is the built-in SFTP subsystem embedded in OpenSSH's sshd daemon, typically invoked via the sshd_config Subsystem directive (e.g., Subsystem sftp internal-sftp -l INFO -d /upload -R -u 0022). Its argument parser processes only the first nine positional arguments; any argument at position 10 or beyond is silently ignored without error or warning. Security-sensitive flags that could appear in later positions include -R (enforce read-only mode), -d (force a start directory), -u (set umask), -P (restrict permission bits), and -l (set audit log verbosity). This is classified as CWE-1284 (Improper Validation of Specified Quantity in Input), reflecting the failure to validate and consume all elements of the provided argument list. The affected CPE string cpe:2.3:a:openbsd:openssh:*:*:*:*:*:*:*:* covers the entire OpenSSH product line across all platforms until the 10.4 release boundary.

RemediationAI

Upgrade to OpenSSH 10.4p1 or later, which corrects the argument-parsing limit in internal-sftp; the official release notes confirming this fix are available at https://www.openssh.org/releasenotes.html#10.4p1. Until a patch can be applied, administrators should audit every sshd_config Subsystem sftp directive and reorder arguments so that all security-critical flags fall within the first nine positions, verifying the effective configuration with sshd -T. If argument reordering is not feasible due to configuration management constraints, consider migrating the SFTP subsystem from internal-sftp to an external binary such as /usr/lib/openssh/sftp-server, which does not share this argument-count limitation; note that this introduces a separate process and potentially a larger attack surface. No compensating controls that fully replicate the missing argument enforcement without either patching or argument reordering have been identified from available references.

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SUSE

Severity: Moderate
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CVE-2026-59997 vulnerability details – vuln.today

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