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libssh EUVDEUVD-2026-46256

| CVE-2026-59848 MEDIUM
Allocation of Resources Without Limits or Throttling (CWE-770)
2026-07-21 redhat GHSA-4h4r-q9xg-gfmm
Denial Of Service Red Hat Enterprise Linux 10 Red Hat Enterprise Linux 8 Red Hat Enterprise Linux 9 Red Hat Hardened Images Red Hat
5.3
CVSS 3.1 · Vendor: redhat
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Severity by source

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

Network vector confirmed; attacker controls server, victim connects; no privileges or user interaction needed beyond the connection itself; availability impact is low (gradual memory growth, not instant crash).

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

Primary rating from Vendor (redhat).

CVSS VectorVendor: redhat

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

Lifecycle Timeline

2
Analysis Generated
Jul 21, 2026 - 14:31 vuln.today
CVE Published
Jul 21, 2026 - 13:21 nvd
MEDIUM 5.3

DescriptionCVE.org

A flaw was found in libssh. A malicious SFTP server can send responses for unknown request IDs that libssh clients keep queued indefinitely, causing unbounded memory growth and client-side denial of service.

AnalysisAI

Unbounded memory growth in libssh's SFTP client allows a malicious server to exhaust client-side memory by sending responses for unknown request IDs, resulting in a denial-of-service condition against any application using libssh for SFTP operations. Affected deployments include libssh as packaged in Red Hat Enterprise Linux 8, 9, 10, and Red Hat Hardened Images. No public exploit code and no active exploitation have been identified at time of analysis; the CVSS score of 5.3 (Medium) reflects the limited availability impact and the requirement that a victim client connect to an attacker-controlled server.

Technical ContextAI

libssh is a C library implementing the SSH2 protocol for both client and server roles, widely packaged in Linux distributions. Its SFTP subsystem tracks outstanding client requests using numeric request IDs and maintains an internal queue of pending operations awaiting server responses. The flaw arises because when a server returns a response referencing an ID not present in the client's outstanding-request table, libssh does not discard the response - it queues it indefinitely. A malicious SFTP server can repeatedly inject bogus response packets with arbitrary unknown IDs, causing the client-side queue to grow without bound and consuming all available heap memory. The CWE classification is not formally assigned in the source data, but the root cause aligns with improper resource release / uncontrolled resource consumption (analogous to CWE-400). The affected packages are identified by CPE strings covering cpe:2.3:a:red_hat:red_hat_enterprise_linux_8, _9, _10, and red_hat_hardened_images.

RemediationAI

Apply the updated libssh package provided by Red Hat for the affected RHEL release via standard package management (dnf update libssh). Consult https://access.redhat.com/security/cve/CVE-2026-59848 for the specific fixed package version once Red Hat publishes the errata; an exact fix version is not independently confirmed from the available data. As a compensating control where immediate patching is not possible, restrict SFTP client applications to connecting only to explicitly trusted, allowlisted SFTP server endpoints using firewall egress rules or application-level hostname/IP allow lists - this directly eliminates the prerequisite of connecting to a malicious server. A trade-off of this control is operational friction for environments with dynamic or user-supplied server endpoints. Monitoring for abnormal memory growth in processes using libssh can provide early detection of exploitation attempts.

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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-2026-46256 vulnerability details – vuln.today
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