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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
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

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L
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. …

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Attack ChainAIDerived

Hypothetical attack flow derived from CVE metadata

Access
Attacker operates malicious SFTP server
Delivery
Victim libssh client initiates SFTP connection
Exploit
Server sends responses with unknown request IDs
Execution
Client queues unknown responses indefinitely
Persist
Client heap memory exhausts
Impact
Client process crashes or hangs
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Vulnerability AssessmentAI

Exploitation Exploitation requires the libssh-based client application to initiate an SFTP session with an attacker-controlled server. … Additional conditions and limiting factors are described in the full assessment.
Risk Assessment The CVSS 5.3 Medium score (AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L) correctly categorises this as a network-reachable, low-complexity denial-of-service with limited availability impact. … Full risk analysis with EPSS, KEV, and SSVC signal comparison available after sign-in.
Exploit Scenario An attacker operates a rogue SFTP server and induces a target application - such as a backup client, CI/CD pipeline, or file-transfer tool - to connect to it, either through DNS poisoning, BGP hijacking, misconfigured server URLs, or social engineering. Once the SFTP session is established, the server continuously returns response packets referencing request IDs that the libssh client never issued, causing the client's internal queue to grow without bound until the process exhausts available memory and crashes or becomes unresponsive. …
Remediation Apply the updated libssh package provided by Red Hat for the affected RHEL release via standard package management (dnf update libssh). … Detailed patch versions, workarounds, and compensating controls in full report.
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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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