CVE-2023-4091

MEDIUMNVD 6.56.5—
EchelonGraph scoreMEDIUM confidence

Score 6.5 from GitHub Security Advisory published 2023-11-03. NVD baseline CVSS 6.5; sources differ by 0.0.

Triggered by: GitHub Security Advisory CVSS
Sources: epss, ghsa, nvd
6.5EG
EchelonGraph verdictMonitorLow exploitation likelihood right now — keep watching.
  • Lower severity and no public exploit yet
CISA-KEV: Not listedEPSS PROB: 1%CVSS: 6.5Exploit: None knownExposed: 0

A fix is available — apply it.

A vulnerability was discovered in Samba, where the flaw allows SMB clients to truncate files, even with read-only permissions when the Samba VFS module "acl_xattr" is configured with "acl_xattr:ignore system acls = yes". The SMB protocol allows opening files when the client requests read-only access but then implicitly truncates the opened file to 0 bytes if the client specifies a separate OVERWRITE create disposition request. The issue arises in configurations that bypass kernel file system permissions checks, relying solely on Samba's permissions.

CVSS v3
6.5
EG Score
6.5(medium)
EG Risk
30(Track)
EG Risk 30/100SSVC: Track

EG Risk is EchelonGraph's 0–100 priority score: it fuses intrinsic severity with real-world exploitation and automatability so you can rank equal-severity CVEs and fix the most dangerous first. Higher = act sooner. Distinct from the 0–10 EG Score (severity).

How it’s computed
Severity65% × 45%
Exploitation1% × 40%
Automatability0% × 15%
Action: Routine — remediate on your standard cadence.
EPSS PROB
1%
EPSS %ILE
64%
KEV
Not listed

Published

November 3, 2023

Last Modified

June 17, 2026

References (23)

Vendor Advisories for CVE-2023-4091(5)

These vendors published their own advisory mentioning this CVE — often with vendor-specific remediation steps + affected product lists not in NVD.

Patch Availability(8)

Vendor / EcosystemFixed in / PatchReleasedSource
ubuntuwinbind (2:4.17.7+dfsg-1ubuntu2.3) @ lunar2026-05-24ubuntu
ubuntuwinbind (2:4.18.6+dfsg-1ubuntu2.1) @ mantic2026-05-24ubuntu
redhatsamba-0:4.18.6-2.el8_92023-11-22redhat
redhatsamba-0:4.17.5-4.el8_82023-11-22redhat
redhatsamba-0:4.17.5-104.el9_22023-11-21redhat
redhatsamba-0:4.15.5-13.el8_62023-11-21redhat
redhatsamba-0:4.18.6-101.el9_32023-11-07redhat
redhatsamba-0:4.15.5-111.el9_02023-10-31redhat

Patches are aggregated from vendor advisories (Red Hat, Microsoft, Cisco, GitHub) and package ecosystems (OSV, GHSA). Multiple rows for the same upstream release have been deduplicated.

Weakness Classification(1)

MITRE Common Weakness Enumeration — the root-cause categories this CVE belongs to.

Additional Vendor Advisories

(3)

Vendors that published advisories for this CVE beyond the curated set above. Broader coverage but minimal per-row detail — click through for the original advisory.

Data Freshness Timeline

(refreshed 11× in last 7d / 46× in last 30d)

Each row is a source pipeline that fetched or updated this CVE on that date, with what changed. For example, "NVD update" means NVD published or revised its analysis for this CVE; "MITRE cvelistV5" means we ingested or refreshed it from the CNA feed. Most recent first.

Showing the most recent 100 of 113 total refreshes for this CVE.

  1. 2026-07-28 15:34 UTCEPSS rescore
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Frequently asked(5)

What is CVE-2023-4091?
CVE-2023-4091 is a medium vulnerability published on November 3, 2023. A vulnerability was discovered in Samba, where the flaw allows SMB clients to truncate files, even with read-only permissions when the Samba VFS module "aclxattr" is configured with "aclxattr:ignore system acls = yes". The SMB protocol allows opening files when the client requests read-only access…
When was CVE-2023-4091 disclosed?
CVE-2023-4091 was first published in the National Vulnerability Database on November 3, 2023, with the most recent update on June 17, 2026. EchelonGraph re-ingests CVE updates from NVD on a 2-hour cycle, so this page reflects the latest published state.
Is CVE-2023-4091 actively exploited?
CVE-2023-4091 is not currently on CISA's Known Exploited Vulnerabilities catalog. FIRST EPSS estimates a 1% probability of exploitation in the next 30 days, which ranks it in the top 35.7% of all scored CVEs.
What is the CVSS score of CVE-2023-4091?
CVE-2023-4091 has a CVSS v3 base score of 6.5 (NVD).
How do I remediate CVE-2023-4091?
Patch to the fixed version published by the affected vendor. Where vendor advisories exist for CVE-2023-4091, EchelonGraph cross-links them in the Vendor Advisories panel below — those typically contain the canonical remediation steps, fixed version numbers, and any vendor-specific mitigations.

Dependency Blast Radius

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