Cyber Resilience

CVE-2023-3603

Memory Safety in Libssh ≤ 0.8.9

Memory Safety
Published
21 July 2023
Modified
21 November 2024
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 0.0090 57th percentile
Risk Priority 30 floored blend · peak EPSS

Summary

CVE-2023-3603 is a low-severity NULL Pointer Dereference (CWE-476) vulnerability in Libssh Libssh. Its CVSS base score is 3.1 (Low).

Operationally, exploitation aligns with the MITRE ATT&CK technique Endpoint Denial of Service (T1499); ranked in the top 43% of CVEs by exploit likelihood; it is not currently listed in the CISA KEV catalog.

OWASP Top 10 for Web (2025)

A10:2025 Mishandling of Exceptional Conditions

EU & UK References

Vulnerability Data

A missing allocation check in sftp server processing read requests may cause a NULL dereference on low-memory conditions. The malicious client can request up to 4GB SFTP reads, causing allocation of up to 4GB buffers, which was not being checked…

more

for failure. This will likely crash the authenticated user's sftp server connection (if implemented as forking as recommended). For thread-based servers, this might also cause DoS for legitimate users. Given this code is not in any released versions, no security releases have been issued.

CWE(s)
CWE-476

Related Threats

MITRE ATT&CK Enterprise Techniques

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 →
T1499.004 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 →
T1489 Service Stop Impact
Adversaries may stop or disable services on a system to render those services unavailable to legitimate users.
attack.mitre.org →
Derived from this CVE’s CWE(s) via the direct CWE→ATT&CK cross-walk.

CVEs Like This One

CVE-2025-8114Same product: Libssh Libssh
CVE-2026-0968Same product: Libssh Libssh
CVE-2025-5987Same product: Libssh Libssh
CVE-2026-3731Same product: Libssh Libssh
CVE-2025-5449Same product: Libssh Libssh
CVE-2023-1667Same product: Libssh Libssh
CVE-2023-53336Shared CWE-476
CVE-2024-50238Shared CWE-476
CVE-2026-43124Shared CWE-476
CVE-2024-50056Shared CWE-476

Affected Assets

libssh
libssh
≤ 0.8.9

Mitigating Controls

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 (static analysis, code review, safe coding standards) directly prevent NULL dereference bugs during development.

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 detect NULL dereference defects before release.

A.8.25 Secure development life cycle partial match
prevents

Secure SDLC mandates defensive coding practices that can prevent NULL dereferences.

A.8.26 Application security requirements partial match
prevents

Application security requirements can specify input validation and pointer-safety rules.

A.8.27 Secure system architecture and engineering principles partial match
prevents

Secure architecture principles encourage defensive design that avoids unsafe pointer use.

A.8.28 Secure coding partial match
prevents

Secure coding standards directly require NULL-pointer checks and safe dereference patterns.

References