← Vulnerability feed

Vulnerability record · CVE-2023-3603 · published 21 July 2023

CVE-2023-3603: Libssh null pointer dereference vulnerability

Libssh · Libssh

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 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.

6.5 CVSS 3.1 Medium EPSS 0.90% · top 41.8% CWE-476 · NULL pointer dereference
6.5CVSS 3.1 base score
0.90%EPSS exploitation probability, 30 days
NoNot in CISA KEV
1Affected product versions listed by NVD
4References
17 Jun 2026Last modified by NVD

Description

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 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.

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

Affected products

1 vulnerable configurations from NVD's CPE data, grouped by vendor and product.

References

LinkTags
https://access.redhat.com/security/cve/CVE-2023-3603 Third Party Advisory
https://bugzilla.redhat.com/show_bug.cgi?id=2221791 Issue TrackingThird Party Advisory
https://access.redhat.com/security/cve/CVE-2023-3603 Third Party Advisory
https://bugzilla.redhat.com/show_bug.cgi?id=2221791 Issue TrackingThird Party Advisory

Track CVE-2023-3603 inside VULONE

Watch it alongside the ransomware crews, C2 infrastructure and forum chatter that reference it, query it through the API and pull it into your SIEM over TAXII.

Start free Open in platform

Related vulnerabilities

Same products first, then exploited flaws of the same weakness class.

9.1CVE-2018-10933libssh server authentication bypass via channel creationlibssh's server-side state machine before 0.7.6 and 0.8.4 allows a client to create channels without completing authentication, bypassing the login s…EPSS 92%analysed8.8CVE-2026-59851Libssh incorrect authorization vulnerabilityA flaw was found in libssh. On servers with GSSAPIKeyExchange enabled, the gssapi-keyex path does not verify whether the authenticated Kerberos princ…EPSS 0.49%8.8CVE-2025-5372Libssh vulnerabilityA flaw was found in libssh versions built with OpenSSL versions older than 3.0, specifically in the ssh_kdf() function responsible for key derivation…EPSS 0.47%8.8CVE-2019-14889Libssh os command injection vulnerabilityA flaw was found with the libssh API function ssh_scp_new() in versions before 0.9.3 and before 0.8.8. When the libssh SCP client connects to a serve…EPSS 3.2%8.2CVE-2026-0966Libssh vulnerabilityA flaw was found in libssh. The API function `ssh_get_hexa()` is vulnerable to a denial of service when processing zero-length input. This can be exp…EPSS 0.58%8.1CVE-2025-5987Libssh vulnerabilityA flaw was found in libssh when using the ChaCha20 cipher with the OpenSSL library. If an attacker manages to exhaust the heap space, this error is n…EPSS 1.6%7.5CVE-2026-59849Libssh vulnerabilityA flaw was found in libssh. Logic errors in automatic certificate-based public key authentication can cause libssh clients to loop indefinitely when …EPSS 0.44%7.5CVE-2026-59850Libssh use after free vulnerabilityA flaw was found in libssh. If data packets are processed after a channel is closed, channel data callbacks can be invoked after the associated data …EPSS 0.60%

Source: NIST National Vulnerability Database (record CVE-2023-3603), CISA KEV, FIRST EPSS (scores of 2026-09-28). This page is refreshed as NVD updates the record.