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CVE-2023-3603· NVD / CVE Program· CNA redhat

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.

MediumCVSS 6.5 · v3.1—No exploit No fix recorded
Published
Jul 21, 2023
Updated
Jun 17, 2026
EPSS
0.9% · 58th percentile
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Action score

26

Monitor

Low priority for now.

CVSS
26 / 40 · 6.5 / 10
CISA KEV
0 / 30 · Not listed
EPSS
0 / 30 · 0.9%

CISA SSVC decision

Exploitation
none
Automatable
no
Technical impact
partial

Vulnrichment: CISA's decision-tree inputs.

CNA vs NVD score

NVD
6.5
CNA · redhat
3.1
3.4 point gap

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

The score given by the assigning authority versus NVD’s independent score. A gap means the severity is contested.

Noroxi analysis

No Noroxi analysis for this record yet

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Affected systems

VendorProduct
libsshlibssh

Affected versions

NVD version ranges (for catalog products). Add the product to your stack with a version and matching uses these.

  • libssh libsshbefore 0.8.9

Versions reported by the vendor

Affected version ranges reported by the assigning authority (redhat). Independent of NVD's CPE analysis and usually ahead of it.

  • Fedora Extra Packages for Enterprise Linux 7

    • all versionsunknown

  • Fedora Fedora

    • all versionsunknown

  • n/a libssh

    • all versionsaffected

  • Red Hat Red Hat Enterprise Linux 7

    • all versionsunknown

  • Red Hat Red Hat Enterprise Linux 8

    • all versionsunknown

  • Red Hat Red Hat Enterprise Linux 9

    • all versionsunknown

Same product

libssh: all records

Other highest-scoring records for the same primary product.

  • CVE-2018-10933A vulnerability was found in libssh's server-side state machine before versions 0.7.6 and 0.8.4.
    64This week
  • CVE-2019-14889A flaw was found with the libssh API function ssh_scp_new() in versions before 0.9.3 and before 0.8.8.
    36Monitor
  • CVE-2026-59851Libssh: libssh: authentication bypass via missing gssapi principal check
    35Monitor
  • CVE-2025-5372Libssh: incorrect return code handling in ssh_kdf() in libssh
    35Monitor
  • CVE-2012-4562Multiple integer overflows in libssh before 0.5.3 allow remote attackers to cause a denial of service (infinite loop or crash) and possibly
    34Monitor
  • CVE-2026-0966Libssh: libssh: denial of service via zero-length input in ssh_get_hexa()
    32Monitor

Remediation

Which version to upgrade to

Fix versions compiled from the vendor, package registries and Microsoft. Verify the vendor's note before upgrading.

No fix version is recorded for this entry. Check the references for vendor advisories.

Exploit status

No known public exploit

No public exploit has been observed yet. That doesn't mean you're safe, only that the bar is a little higher.

Research context

For pentesters and researchers: attack profile, score disagreement, timeline, patch commits, credits, variant and chain candidates, bug bounty scope. All derived from existing data; no exploit code.

Timeline

From publication to today: proof of concept, Metasploit module, CISA KEV and fix record. Dates are as reported by the sources.

No dated events beyond publication.

EPSS, last 120 days

FIRST EPSS daily score; only changes of 0.01 or more are recorded (step chart).

Patch and commit links

Commit, PR and diff links among the references. A starting point for patch-diffing and variant hunting; fixes, not exploits.

No commit or PR link among the references.

Credits

All researchers

Finders, reporters and analysts named in the CNA record. Click a name for that researcher’s other records.

Variant candidates

Same product, same weakness class, within 18 months. If the patch missed the root cause, the sibling bug is here.

No nightly-computed relations.

Chain candidates

An authentication bypass and a privilege-requiring bug in the same product, published close together: combined they may become an unauthenticated path.

—

Bug bounty scope

No known public program.

Source: bounty-targets-data (public HackerOne, Bugcrowd, Intigriti, YesWeHack listings).

Technical details

Attack conditions

  • Anyone who can reach it over the internet can trigger it.
  • A low-privileged account is enough.
  • No user action is required.
  • No special conditions are required; it is repeatable.

If successful

Confidentiality
none
Integrity
none
Availability
high · the service can be disrupted
Attack vector
Network
Attack complexity
Low
Privileges required
Low
User interaction
None
Scope
Unchanged
Confidentiality impact
None
Integrity impact
None
Availability impact
High

Weakness class (CWE)

CWE-476 · NULL Pointer Dereference

CVSS vector

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

nvd-primary

Attack context

MITRE CAPEC attack patterns and ATT&CK techniques for this weakness class (CWE). A starting point for detection rules and threat hunting.

MITRE has no CAPEC/ATT&CK mapping for this CWE.

Change log

No changes recorded on tracked fields yet. Score, KEV, exploit maturity and fix status changes appear here.

References

Vendor advisories and official records. Exploit/PoC links are deliberately left out.

All records