CVE-2023-3603Network attack vector

Authenticated service interruption via unchecked SFTP allocation

Published Jul 21, 2023 · Updated Sep 26, 2024

NULL pointer dereference in libssh master-branch SFTP server code allows remote authenticated users to crash a server connection. The process_read handler allocates a buffer matching an SFTP read length of up to 4 GB, then uses the result without checking for allocation failure. Exploitation requires authenticated SFTP access and low-memory conditions; forking servers lose one connection, while thread-based servers can interrupt service for other users.

CVSS severity3.1
Low
EPSS probability0.90%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

NULL pointer dereference in libssh master-branch SFTP server code allows remote authenticated users to crash a server connection. The process_read handler allocates a buffer matching an SFTP read length of up to 4 GB, then uses the result without checking for allocation failure. Exploitation requires authenticated SFTP access and low-memory conditions; forking servers lose one connection, while thread-based servers can interrupt service for other users.

The record

CVE
CVE-2023-3603
Published
Jul 21, 2023
Updated
Sep 26, 2024
Vendor
libssh
Product
libssh
Classifications
CWE-476, T1499
Attack vector
network
Privileges
authenticated

Timeline

How it unfolded

  1. Jul 21, 2023CVE publishedPublication date reported by the CVE source.
  2. Sep 26, 2024Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

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Is a vulnerable build present?

Affected versions are unavailable in this record. Check the vendor advisory for version and patch details.

What conditions does exploitation require?

Attack vectornetwork
Required privilegesauthenticated

What is affected?

libssh · libsshAffected versions are unavailable in this record.

Published CVSS scores

6.5NIST NVDCVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H
3.1libsshCVSS:3.0/AV:N/AC:H/PR:L/UI:N/S:U/C:N/I:N/A:L

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

Daily unique IPsNo honeypot observations are available for this CVE in the selected window.

No observations available

Sep 10, 2026Sep 16, 2026
Latest reporting daySep 16, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-476NULL Pointer Dereference
T1499Endpoint Denial of Service

Public exploit references

No public exploit references are available in this record.

Labels summarize the accepted research assessment. They do not indicate a test against your environment.

Technologies

Your stack

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Your stack

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