CVE-2026-4408

CRITICALNVD 9.89.8—
EchelonGraph scoreMEDIUM confidence

This critical-severity CVE scores 9.8 under NVD CVSS v3. EPSS exploit probability: 2.5%, top 16% of all CVEs by exploit prediction. GitHub Security Advisory enrichment pending alignment with NVD CVSS.

Triggered by: NVD CVSS baseline
Sources: epss, ghsa, nvd
Trending — Patch released this weekElevated
9.8EG
EchelonGraph verdictPlan a fixSerious severity, but no confirmed exploitation yet.
  • High severity, but no confirmed exploitation yet
CISA-KEV: Not listedEPSS PROB: 3%CVSS: 9.8Exploit: Elevated riskExposed: 0

A fix is available — apply it.

A flaw was found in Samba. A remote attacker can exploit a misconfiguration in Samba file servers and classic domain controllers that use the "check password script" feature. If this script is configured with the %u substitution character, the client-controlled username is passed without proper escaping of shell meta-characters. This vulnerability allows an attacker to achieve remote command execution on the affected system. This issue primarily affects non-standard configurations where the "check password script" is used with %u and the samba-dcerpcd service is started as a system service.

CVSS v3
9.8
EG Score
9.8(medium)
EG Risk
60(Track)
EG Risk 60/100SSVC: 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
Severity98% × 45%
Exploitation40% × 40%
Automatability0% × 15%
Action: Routine — remediate on your standard cadence.
EPSS PROB
3%
EPSS %ILE
84%
KEV
Not listed

Published

May 28, 2026

Last Modified

September 18, 2026

Advisory Details (13)

Auto-updated Sep 18, 2026
Patch available. Sources: redhat.
redhat Patch Available

Affected: Red Hat Enterprise Linux 8.4 Advanced Mission Critical Update Support and Red Hat Enterprise Linux 8.4 Extended Update Support

https://access.redhat.com/errata/RHSA-2026:28058
redhat Patch Available

Affected: Red Hat Enterprise Linux 8.6 Advanced Mission Critical Update Support and Red Hat Enterprise Linux 8.6 Extended Update Support

https://access.redhat.com/errata/RHSA-2026:28057
redhat Patch Available

Affected: Red Hat Enterprise Linux 8.8 Update Services for SAP Solutions and Red Hat Enterprise Linux 8.8 Telecommunications Update Serv

https://access.redhat.com/errata/RHSA-2026:28056
redhat Patch Available

Affected: Red Hat Enterprise Linux 10.0 Extended Update Support.

https://access.redhat.com/errata/RHSA-2026:28055
redhat Patch Available

Affected: Red Hat Enterprise Linux 9.2 Update Services for SAP Solutions.

https://access.redhat.com/errata/RHSA-2026:28054
redhat Patch Available

Affected: Red Hat Enterprise Linux 9.4 Update Services for SAP Solutions.

https://access.redhat.com/errata/RHSA-2026:28053
redhat Patch Available

Affected: Red Hat Enterprise Linux 9.6 Extended Update Support.

https://access.redhat.com/errata/RHSA-2026:25979
redhat Patch Available

Affected: Red Hat Enterprise Linux 9.

https://access.redhat.com/errata/RHSA-2026:25049
redhat Patch Available

Affected: Red Hat Enterprise Linux 10.

https://access.redhat.com/errata/RHSA-2026:22963
redhat Patch Available

Affected: Red Hat Enterprise Linux 8.

https://access.redhat.com/errata/RHSA-2026:22644
redhat Patch Available

cve-details

https://access.redhat.com/security/cve/CVE-2026-4408
generic

16034 – (CVE-2026-4408) CVE-2026-4408 [SECURITY] Remote Code Execution in SAMR

https://bugzilla.samba.org/show_bug.cgi?id=16034
redhat Patch Available

2479762 – (CVE-2026-4408) CVE-2026-4408 samba: Remote Code Execution in SAMR

Affected: Red Hat Enterprise Linux 8

https://bugzilla.redhat.com/show_bug.cgi?id=2479762

Vendor Advisories for CVE-2026-4408(20)

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

Patch Availability(22)

Vendor / EcosystemFixed in / PatchReleasedSource
ubuntuwinbind (2:4.23.6+dfsg-1ubuntu2.1) @ resolute2026-09-18ubuntu
redhatrhcos-413.92.202609080414-02026-09-17redhat
redhatrhcos-412.86.202608241157-02026-09-03redhat
redhatrhcos-417.94.202608250221-02026-09-03redhat
redhatrhcos-416.94.202608150307-02026-08-31redhat
redhatrhcos-414.92.202608172040-02026-08-31redhat
redhatrhcos-415.92.202608180329-02026-08-31redhat
redhatrhcos-418.94.202608142238-02026-08-26redhat
redhatrhcos-4.19.9.6.202606241344-02026-07-02redhat
redhatrhcos-4.20.9.6.202606241928-02026-06-30redhat
redhatrhcos-4.21.9.6.202606241859-02026-06-30redhat
redhatsamba-0:4.10.16-26.el7_9.12026-06-23redhat
redhatsamba-0:4.13.3-12.el8_4.12026-06-23redhat
redhatsamba-0:4.15.5-16.el8_6.12026-06-23redhat
redhatsamba-0:4.17.5-7.el8_8.12026-06-23redhat
redhatsamba-0:4.19.4-105.el9_4.42026-06-23redhat
redhatsamba-0:4.21.3-114.el10_0.12026-06-23redhat
redhatsamba-0:4.17.5-105.el9_2.52026-06-23redhat
redhatsamba-0:4.21.3-14.el9_6.12026-06-15redhat
redhatsamba-0:4.23.5-10.el9_82026-06-10redhat
redhatsamba-0:4.23.5-109.el10_22026-06-03redhat
redhatsamba-0:4.19.4-16.el8_102026-06-03redhat

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.

Affected Packages

(6 across 6 ecosystems)
Alpine:v3.23(1)
PackageVulnerable rangeFixed inDependents
samba—4.22.10-r0—
Alpine:v3.24(1)
PackageVulnerable rangeFixed inDependents
samba—4.23.8-r0—
Debian:11(1)
PackageVulnerable rangeFixed inDependents
samba2:4.13.13+dfsg-1~deb11u1 ... 2:4.13.5+dfsg-2 (8 versions)2:4.13.13+dfsg-1~deb11u8—
Debian:12(1)
PackageVulnerable rangeFixed inDependents
samba2:4.17.10+dfsg-0+deb12u1 ... 2:4.17.9+dfsg-0+deb12u3~bpo11+1 (13 versions)2:4.17.12+dfsg-0+deb12u4—
Debian:13(1)
PackageVulnerable rangeFixed inDependents
samba2:4.22.3+dfsg-4 ... 2:4.22.8+dfsg-0+deb13u1 (7 versions)2:4.22.8+dfsg-0+deb13u2—
Debian:14(1)
PackageVulnerable rangeFixed inDependents
samba2:4.22.3+dfsg-4 ... 2:4.24.3+dfsg-1~bpo13+1 (30 versions)2:4.24.3+dfsg-1—

Weakness Classification(1)

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

Additional Vendor Advisories

(2)

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 17× in last 7d / 123× 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 673 total refreshes for this CVE.

  1. 2026-09-18 19:28 UTCEPSS rescore
  2. 2026-09-18 13:23 UTCVendor advisory
  3. 2026-09-18 13:23 UTCGHSA enrichment
  4. 2026-09-18 12:19 UTCEG score recompute
  5. 2026-09-18 12:19 UTCVendor advisory
  6. 2026-09-18 12:19 UTCGHSA enrichment
  7. 2026-09-17 19:28 UTCVendor advisory
  8. 2026-09-17 19:28 UTCGHSA enrichment
  9. 2026-09-17 18:29 UTCEG score recompute
  10. 2026-09-17 18:29 UTCVendor advisory
  11. 2026-09-17 18:29 UTCGHSA enrichment
  12. 2026-09-16 14:08 UTCEPSS rescore
  13. 2026-09-16 05:15 UTCEPSS rescore
  14. 2026-09-14 07:30 UTCEG score recompute
  15. 2026-09-14 07:30 UTCVendor advisory
  16. 2026-09-14 07:30 UTCGHSA enrichment
  17. 2026-09-13 16:47 UTCEPSS rescore
  18. 2026-09-11 14:53 UTCEPSS rescore
  19. 2026-09-10 09:35 UTCEPSS rescore
  20. 2026-09-08 22:01 UTCEPSS rescore
  21. 2026-09-07 16:01 UTCEPSS rescore
  22. 2026-09-06 13:47 UTCEPSS rescore
  23. 2026-09-04 13:29 UTCVendor advisory
  24. 2026-09-04 13:29 UTCGHSA enrichment
  25. 2026-09-04 12:21 UTCEG score recompute
Show 75 more
  1. 2026-09-04 12:21 UTCVendor advisory
  2. 2026-09-04 12:21 UTCGHSA enrichment
  3. 2026-09-04 05:06 UTCEPSS rescore
  4. 2026-09-03 15:32 UTCVendor advisory
  5. 2026-09-03 15:32 UTCGHSA enrichment
  6. 2026-09-03 14:22 UTCVendor advisory
  7. 2026-09-03 14:21 UTCGHSA enrichment
  8. 2026-09-03 13:19 UTCVendor advisory
  9. 2026-09-03 13:19 UTCGHSA enrichment
  10. 2026-09-03 12:28 UTCEG score recompute
  11. 2026-09-03 12:28 UTCVendor advisory
  12. 2026-09-03 12:28 UTCGHSA enrichment
  13. 2026-09-02 14:12 UTCEPSS rescore
  14. 2026-09-01 13:54 UTCEPSS rescore
  15. 2026-09-01 13:47 UTCVendor advisory
  16. 2026-09-01 13:47 UTCGHSA enrichment
  17. 2026-09-01 13:44 UTCGHSA enrichment
  18. 2026-09-01 12:20 UTCVendor advisory
  19. 2026-09-01 12:19 UTCGHSA enrichment
  20. 2026-09-01 11:57 UTCEG score recompute
  21. 2026-09-01 11:57 UTCVendor advisory
  22. 2026-09-01 11:57 UTCGHSA enrichment
  23. 2026-09-01 04:40 UTCEPSS rescore
  24. 2026-08-31 17:24 UTCVendor advisory
  25. 2026-08-31 17:24 UTCGHSA enrichment
  26. 2026-08-31 17:07 UTCVendor advisory
  27. 2026-08-31 17:06 UTCGHSA enrichment
  28. 2026-08-31 13:31 UTCVendor advisory
  29. 2026-08-31 13:31 UTCGHSA enrichment
  30. 2026-08-31 12:30 UTCVendor advisory
  31. 2026-08-31 12:30 UTCGHSA enrichment
  32. 2026-08-31 03:20 UTCVendor advisory
  33. 2026-08-31 03:20 UTCGHSA enrichment
  34. 2026-08-31 02:34 UTCEG score recompute
  35. 2026-08-31 02:34 UTCVendor advisory
  36. 2026-08-31 02:34 UTCGHSA enrichment
  37. 2026-08-30 19:17 UTCEPSS rescore
  38. 2026-08-30 01:22 UTCEPSS rescore
  39. 2026-08-28 21:41 UTCEPSS rescore
  40. 2026-08-27 14:25 UTCEPSS rescore
  41. 2026-08-27 13:35 UTCVendor advisory
  42. 2026-08-27 13:35 UTCGHSA enrichment
  43. 2026-08-27 13:01 UTCVendor advisory
  44. 2026-08-27 13:01 UTCGHSA enrichment
  45. 2026-08-26 17:44 UTCVendor advisory
  46. 2026-08-26 17:44 UTCGHSA enrichment
  47. 2026-08-26 16:23 UTCEG score recompute
  48. 2026-08-26 16:23 UTCVendor advisory
  49. 2026-08-26 16:23 UTCGHSA enrichment
  50. 2026-08-26 14:46 UTCEPSS rescore
  51. 2026-08-26 13:26 UTCVendor advisory
  52. 2026-08-26 13:25 UTCGHSA enrichment
  53. 2026-08-26 12:20 UTCVendor advisory
  54. 2026-08-26 12:20 UTCGHSA enrichment
  55. 2026-08-25 16:28 UTCVendor advisory
  56. 2026-08-25 16:28 UTCGHSA enrichment
  57. 2026-08-25 16:11 UTCEG score recompute
  58. 2026-08-25 16:11 UTCVendor advisory
  59. 2026-08-25 16:11 UTCGHSA enrichment
  60. 2026-08-25 13:49 UTCEPSS rescore
  61. 2026-08-25 13:23 UTCVendor advisory
  62. 2026-08-25 13:23 UTCGHSA enrichment
  63. 2026-08-25 12:19 UTCVendor advisory
  64. 2026-08-25 12:19 UTCGHSA enrichment
  65. 2026-08-25 05:07 UTCEG score recompute
  66. 2026-08-25 05:07 UTCVendor advisory
  67. 2026-08-25 05:07 UTCGHSA enrichment
  68. 2026-08-24 13:29 UTCVendor advisory
  69. 2026-08-24 13:29 UTCGHSA enrichment
  70. 2026-08-24 12:24 UTCEG score recompute
  71. 2026-08-24 12:24 UTCVendor advisory
  72. 2026-08-24 12:24 UTCGHSA enrichment
  73. 2026-08-23 23:56 UTCVendor advisory
  74. 2026-08-23 23:56 UTCGHSA enrichment
  75. 2026-08-23 18:48 UTCVendor advisory

Publicly available exploits

(1 reference)

Working exploit code is in the public domain (1 GitHub PoC). Defenders should treat patch urgency accordingly — public PoCs typically lead to mass-exploitation within 24-72 hours.

  • GitHub PoCSafeBreach-Labs/ForgottenButNotGone
    First seen Aug 3, 2026

    proof-of-concept scripts for 2 unauthenticated RCEs in Samba (CVE-2026-4408 & CVE-2026-4480) and local privilege escalation in TelnetD (CVE-2026-28372)

    Open source ↗

Frequently asked(5)

What is CVE-2026-4408?
CVE-2026-4408 is a critical vulnerability published on May 28, 2026. A flaw was found in Samba. A remote attacker can exploit a misconfiguration in Samba file servers and classic domain controllers that use the "check password script" feature. If this script is configured with the %u substitution character, the client-controlled username is passed without proper…
When was CVE-2026-4408 disclosed?
CVE-2026-4408 was first published in the National Vulnerability Database on May 28, 2026, with the most recent update on September 18, 2026. EchelonGraph re-ingests CVE updates from NVD on a 2-hour cycle, so this page reflects the latest published state.
Is CVE-2026-4408 actively exploited?
CVE-2026-4408 is not currently on CISA's Known Exploited Vulnerabilities catalog. FIRST EPSS estimates a 3% probability of exploitation in the next 30 days, which ranks it in the top 16.0% of all scored CVEs.
What is the CVSS score of CVE-2026-4408?
CVE-2026-4408 has a CVSS v3 base score of 9.8 (NVD).
How do I remediate CVE-2026-4408?
Patch to the fixed version published by the affected vendor. Where vendor advisories exist for CVE-2026-4408, 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

See which npm, PyPI, Go, and Maven packages are affected by CVE-2026-4408

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