CVE-2023-3603 | Processing sftp server read may cause null dereference

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.

Published: 2023-07-21 Last update: 2024-11-21 Assigner: [email protected] Source: [email protected]
NVD Status：Modified，CVE State: published
View at NVD, CVE.org, EUVD

CVE-2023-3603 is rated Low Risk (30.7/100): CVSS Low severity, with medium exploitation likelihood (EPSS 0.77%). Monitor for updates and reassess as exploit intelligence or EPSS changes.

Risk is dynamic; we continuously reassess and refresh what is shown on this page as upstream context changes.

Exploit prediction scoring system (EPSS) score for CVE-2023-3603

EPSS lead: Daily EPSS estimates relative likelihood of exploitation; percentile ranks this CVE among scored vulnerabilities (higher = more severe relative rank).

# Date Old EPSS score New EPSS score Delta (New - Old)
1 2026-06-15 0.12% 0.77% +0.65%
2 2025-11-21 0.45% 0.12% -0.33%
3 2025-11-18 — 0.45% —

Full EPSS history (17 records total)

Common vulnerability scoring system (CVSS) metrics for CVE-2023-3603

CVSS metrics for this CVE.

Base score Version Severity Vector Exploitability Impact Score source
3.1 3.1 LOW
CVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:U/C:N/I:N/A:L Click to expand
Attack vector (AV:N)
Could be attacked over the internet or any normal routed network—not just someone sitting at the machine.
Attack complexity (AC:H)
Even with access, the exploit needs extra luck, timing, or a fussy environment to actually work.
Privileges required (PR:L)
A normal user session is enough; they don’t have to be admin.
User interaction (UI:N)
Nobody has to click “OK” or open a trap file; it can work without a victim helping.
Scope (S:U)
Damage stays in the same “trust bubble” as the broken component—no big spill into unrelated systems.
Confidentiality (C:N)
Doesn’t really leak secrets in a meaningful way.
Integrity (I:N)
Data isn’t meaningfully altered or forged.
Availability (A:L)
Might cause slowdowns, glitches, or partial disruption—not a full brick.
 1.6 1.4 [email protected]
6.5 3.1 MEDIUM
CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H Click to expand
Attack vector (AV:N)
Could be attacked over the internet or any normal routed network—not just someone sitting at the machine.
Attack complexity (AC:L)
Once they can reach the bug, pulling it off is straightforward—no weird race conditions or rare setup.
Privileges required (PR:L)
A normal user session is enough; they don’t have to be admin.
User interaction (UI:N)
Nobody has to click “OK” or open a trap file; it can work without a victim helping.
Scope (S:U)
Damage stays in the same “trust bubble” as the broken component—no big spill into unrelated systems.
Confidentiality (C:N)
Doesn’t really leak secrets in a meaningful way.
Integrity (I:N)
Data isn’t meaningfully altered or forged.
Availability (A:H)
Could take the service down hard or make it unusable for people who depend on it.
 2.8 3.6 [email protected]

Weakness enumeration for CVE-2023-3603

OS Trackers for CVE-2023-3603

vendor priority summary link
alpine — CVE-2023-3603: 1 source package rows (libssh); 2 state rows across 2 repos (3.22-community, edge-community); fixed 0, open 2. https://security.alpinelinux.org/vuln/CVE-2023-3603
debian unimportant CVE-2023-3603 unimportant priority: Debian including 1 source packages (libssh), 5 status rows across 5 suites (bookworm, bullseye, forky, sid, trixie): resolved 5. https://security-tracker.debian.org/tracker/CVE-2023-3603
redhat low — https://access.redhat.com/security/cve/CVE-2023-3603
suse medium CVE-2023-3603 severity moderate: SUSE including 6 source package names (libssh, libssh-config, libssh-devel, libssh-devel-doc, libssh4, libssh4-32bit), 126 product×package rows across 34 product lines (SUSE CaaS Platform 4.0, SUSE Enterprise Storage 7, … (34 product lines)): Known Not Affected 126. https://www.suse.com/security/cve/CVE-2023-3603/
ubuntu medium CVE-2023-3603 medium priority: Ubuntu including 1 source packages (libssh), 8 status rows across 8 suites (bionic, focal, jammy, kinetic, lunar, trusty, upstream, xenial): not-affected 7, ignored 1. https://ubuntu.com/security/CVE-2023-3603

Affected software / configurations for CVE-2023-3603

Vendor Product Version Raw CPE
libssh libssh < 0.8.9 cpe:2.3:a:libssh:libssh:*:*:*:*:*:*:*:*

References for CVE-2023-3603

URL Tags
https://access.redhat.com/security/cve/CVE-2023-3603 Third Party Advisory
https://bugzilla.redhat.com/show_bug.cgi?id=2221791 Issue Tracking Third Party Advisory
cvelogic Threat Intelligence