Cyber Resilience

CVE-2026-59849

DoS in Libssh

DoS
Published
21 July 2026
Modified
30 July 2026
Patch / advisory
View advisory
CVSS Score v3.1 3.1
Click a component to see what it means
Raw vectorCVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:U/C:N/I:N/A:L
EPSS Score 0.0024 15th percentile
Risk Priority 27 floored blend · peak EPSS

Summary

CVE-2026-59849 is a low-severity Infinite Loop (CWE-835) vulnerability in Libssh Libssh. Its CVSS base score is 3.1 (Low).

Operationally, exploitation aligns with the MITRE ATT&CK technique Application or System Exploitation (T1499.004); ranked at the 15th percentile by exploit likelihood (below the median); it is not currently listed in the CISA KEV catalog.

The strongest mitigations our analysis identified map to SA-11 (Developer Testing and Evaluation) and SI-2 (Flaw Remediation) — see the control section below for these in your framework.

EU & UK References

Vulnerability Data

A flaw was found in libssh. Logic errors in automatic certificate-based public key authentication can cause libssh clients to loop indefinitely when configured certificates are missing or repeatedly rejected by a server, leading to denial of service.

CWE(s)
CWE-835

Related Threats

MITRE ATT&CK Enterprise Techniques

T1499.004 Application or System Exploitation Impact
Adversaries may exploit software vulnerabilities that can cause an application or system to crash and deny availability to users.
attack.mitre.org →
T1499 Endpoint Denial of Service Impact
Adversaries may perform Endpoint Denial of Service (DoS) attacks to degrade or block the availability of services to users.
attack.mitre.org →
T1499.003 Application Exhaustion Flood Impact
Adversaries may target resource intensive features of applications to cause a denial of service (DoS), denying availability to those applications.
attack.mitre.org →
Derived from this CVE’s CWE(s) via the direct CWE→ATT&CK cross-walk.

CVEs Like This One

CVE-2026-59843Same product: Libssh Libssh
CVE-2026-59844Same product: Libssh Libssh
CVE-2026-59848Same product: Libssh Libssh
CVE-2026-59851Same product: Libssh Libssh
CVE-2026-59842Same product: Libssh Libssh
CVE-2026-59850Same product: Libssh Libssh
CVE-2026-59846Same product: Libssh Libssh
CVE-2026-15370Same product: Libssh Libssh
CVE-2026-59847Same product: Libssh Libssh
CVE-2026-59845Same product: Libssh Libssh

Affected Assets

libssh
libssh
all versions
redhat
hardened images
all versions
redhat
enterprise linux
10.0

Mitigating Controls

Mitigating Controls (NIST 800-53 r5) AI

SA-11 Developer Testing and Evaluation good match

Developer testing and evaluation can discover unreachable loop exit conditions through static analysis, fuzzing, or execution tracing.

SI-2 Flaw Remediation good match

Flaw remediation processes identify and correct infinite-loop defects reported from testing or operations.

SA-15 Development Process, Standards, and Tools partial match

Requiring documented development processes and secure coding standards reduces introduction of loops whose termination conditions are unreachable.

Mitigating Controls (NIST CSF 2.0) AI

Derived directly from the weakness types (CWEs) cited in the NVD entry via our AI-authored CWE→CSF cross-walk (authority under review) — links open the control.

PR.PS-06 mostly match
prevents

Secure SDLC practices (reviews, testing, static analysis) directly prevent introduction of infinite-loop defects.

ID.RA-01 partial match
prevents

Static analysis and vuln scanning during asset assessment can detect unreachable loop exits.

Mitigating Controls (ISO/IEC 27001:2022 Annex A) AI

Derived directly from the weakness types (CWEs) cited in the NVD entry via our AI-authored CWE→ISO cross-walk (authority under review) — links open the control.

A.8.29 Security testing in development and acceptance mostly match
finds

Security testing can uncover infinite-loop conditions before release.

A.8.25 Secure development life cycle partial match
prevents

Secure development life cycle mandates practices that can detect and prevent infinite-loop defects.

A.8.26 Application security requirements partial match
prevents

Application security requirements can specify loop-termination rules, indirectly reducing the weakness.

A.8.28 Secure coding partial match
prevents

Secure coding standards directly address loop termination and prevent infinite loops.

A.8.27 Secure system architecture and engineering principles none match
none

Secure architecture principles encourage designs that avoid unreachable exit conditions.

A.8.32 Change management none match
none

Change management can require review of loop logic when code is modified.

References