CVE-2023-3603

Processing sftp server read may cause null dereference

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.

Remediation

Workaround:

  • The SFTP server implementation is based on callbacks so you can rewrite the sftp_channel_default_data_callback() to provide additional checks. [1] https://gitlab.com/libssh/libssh-mirror/-/blob/master/examples/sample_sftpserver.c#L330

Category

3.1
CVSS
Severity: Low
CVSS 3.1 •
EPSS 0.12%
Third-Party Advisory redhat.com Third-Party Advisory redhat.com
Affected: n/a libssh
Affected: Red Hat Red Hat Enterprise Linux 7
Affected: Red Hat Red Hat Enterprise Linux 8
Affected: Red Hat Red Hat Enterprise Linux 9
Affected: Fedora Extra Packages for Enterprise Linux 7
Affected: Fedora Fedora
Published at:
Updated at:

References

Link Tags
https://access.redhat.com/security/cve/CVE-2023-3603 third party advisory vdb entry
https://bugzilla.redhat.com/show_bug.cgi?id=2221791 third party advisory issue tracking

Frequently Asked Questions

What is the severity of CVE-2023-3603?
CVE-2023-3603 has been scored as a low severity vulnerability.
How to fix CVE-2023-3603?
As a workaround for remediating CVE-2023-3603: The SFTP server implementation is based on callbacks so you can rewrite the sftp_channel_default_data_callback() to provide additional checks. [1] https://gitlab.com/libssh/libssh-mirror/-/blob/master/examples/sample_sftpserver.c#L330
Is CVE-2023-3603 being actively exploited in the wild?
As for now, there are no information to confirm that CVE-2023-3603 is being actively exploited. According to its EPSS score, there is a ~0% probability that this vulnerability will be exploited by malicious actors in the next 30 days.
What software or system is affected by CVE-2023-3603?
CVE-2023-3603 affects n/a libssh, Red Hat Red Hat Enterprise Linux 7, Red Hat Red Hat Enterprise Linux 8, Red Hat Red Hat Enterprise Linux 9, Fedora Extra Packages for Enterprise Linux 7, Fedora Fedora.
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