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libssh EUVDEUVD-2026-46179

| CVE-2026-59844 MEDIUM
Memory Allocation with Excessive Size Value (CWE-789)
2026-07-21 redhat GHSA-qp28-hpg5-j7xc
6.5
CVSS 3.1 · Vendor: redhat
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Severity by source

Vendor (redhat) PRIMARY
6.5 MEDIUM
AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H
vuln.today AI
6.5 MEDIUM

Network-reachable SFTP server, no complexity, low-privilege auth required; purely availability impact via uncontrolled memory allocation.

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

Primary rating from Vendor (redhat).

CVSS VectorVendor: redhat

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

Lifecycle Timeline

2
Analysis Generated
Jul 21, 2026 - 12:31 vuln.today
CVE Published
Jul 21, 2026 - 11:32 nvd
MEDIUM 6.5

DescriptionCVE.org

A flaw was found in libssh. A remote authenticated client can issue SSH_FXP_READ requests with an arbitrarily large length, causing a libssh SFTP server to allocate excessive memory and potentially exhaust it through repeated requests.

AnalysisAI

Memory exhaustion in libssh's SFTP server subsystem allows authenticated remote clients to degrade or crash the service by sending SSH_FXP_READ requests specifying an arbitrarily large read length, causing the server to allocate unbounded memory for each request. The CVSS vector (PR:L) confirms exploitation requires valid credentials, limiting the attack surface to authenticated SFTP users. No public exploit code and no CISA KEV listing have been identified at time of analysis, though the low complexity and network-accessible attack path make this a realistic insider or credential-abuse scenario.

Technical ContextAI

libssh is a C library implementing the SSHv2 protocol, widely packaged in enterprise Linux distributions including Red Hat Enterprise Linux 8, 9, and 10 and Red Hat Hardened Images (per CPE data: cpe:2.3:a:red_hat:red_hat_enterprise_linux_*). The SFTP subsystem handles SSH_FXP_READ messages, which include a client-specified length field indicating how many bytes to return. CWE-789 (Uncontrolled Memory Allocation) identifies the root cause: the server fails to validate or cap this length field before allocating memory proportional to the client-supplied value. Repeated requests with large length values progressively exhaust server-side memory. This is a server-side flaw in the libssh SFTP daemon code path, not in the client library.

RemediationAI

Apply the vendor-released patch via Red Hat's standard update mechanism (yum/dnf update libssh) once a fixed package is published for the affected RHEL version; consult https://access.redhat.com/security/cve/CVE-2026-59844 for the current patch status and exact fixed package version. No specific fixed version number was confirmed in the provided data - do not assume a version without verifying against the Red Hat advisory. As an interim compensating control, restrict SFTP subsystem access to only explicitly authorized users using AllowUsers or Match blocks in sshd_config, which reduces the population of potential attackers at the cost of operational flexibility. Additionally, applying connection rate limiting (MaxStartups, MaxSessions in sshd_config) can slow repeated request flooding, though it will not prevent a single authenticated user from issuing many large-length reads within an established session. Monitoring for abnormal memory consumption on the SFTP daemon process can provide early detection.

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Vendor StatusVendor

SUSE

Severity: Moderate
Product Status
SUSE Linux Enterprise Module for Basesystem 15 SP7 Affected
SUSE Linux Enterprise Server 15 SP7 Affected
SUSE Linux Enterprise Desktop 15 SP7 Affected
SUSE Linux Enterprise Server for SAP Applications 15 SP7 Affected
SUSE Linux Enterprise High Performance Computing 15 SP7 Affected

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EUVD-2026-46179 vulnerability details – vuln.today

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