CVE-2021-36934

CRITICALNVD 7.89.0
EchelonGraph scoreHIGH confidence

“▲” beside the score: it is higher than NVD's CVSS score.

Score elevated to 9.0 because this CVE is listed on the CISA Known Exploited Vulnerabilities catalog (added 2022-02-10), indicating real-world exploitation has been confirmed by US federal agencies. NVD baseline CVSS 7.8 retained for reference. The 9.0 is the floor for confirmed exploitation, not an impact rating: this CVE's impact severity (EG Severity) is CVSS 7.8 HIGH under GitHub Security Advisory CVSS. Confidence: HIGH.

Triggered by: CISA KEV (actively exploited)
Sources: CISA Known Exploited Vulnerabilities catalog, EPSS, GitHub Security Advisory, NVD CVSS v3
Trending — 4 sources updated this weekExploited in the wild

Also known asEUVD-2021-23510 (ENISA EUVD) · GHSA-x4m2-px5g-5q55 (GitHub Security Advisories)Source: ENISA EUVD

9.0EG
EchelonGraph verdictPatch nowTreat as an emergency — this is being exploited.
  • Actively exploited in the wild (CISA-KEV) — the reason this is sooner than the SSVC decision on this page at low or medium mission impact
CISA-KEV: ExploitedEPSS PROB: 67%CVSS: 7.8Exploit: Metasploit · other public PoCExposed services: Not assessed

A fix is available — apply it.

An elevation of privilege vulnerability exists because of overly permissive Access Control Lists (ACLs) on multiple system files, including the Security Accounts Manager (SAM) database. An attacker who successfully exploited this vulnerability could run arbitrary code with SYSTEM privileges. An attacker could then install programs; view, change, or delete data; or create new accounts with full user rights. An attacker must have the ability to execute code on a victim system to exploit this vulnerability. After installing this security update, you must manually delete all shadow copies of system files, including the SAM database, to fully mitigate this vulnerabilty. Simply installing this security update will not fully mitigate this vulnerability. See KB5005357- Delete Volume Shadow Copies.

CVSS v3
7.8
EG Score
9.0CRITICALhigh confidence
EG Risk
75
EG Risk 75/100

EG Risk is EchelonGraph's 0–100 priority score. It fuses impact severity (EG Severity, the CVSS base score, never the KEV-floored or EPSS-lifted EG Score) with real-world exploitation and automatability, under weights EchelonGraph set by hand, so you can rank equal-severity CVEs and fix the most dangerous first. Higher = act sooner.

How it’s computed (value × EchelonGraph’s weight)
Severity78% × 45%
Impact severity (EG Severity): CVSS 7.8 of 10. Never the KEV-floored or EPSS-lifted EG Score.
Exploitation100% × 40%
Fixed at 100% for a CISA KEV listing: EchelonGraph's rule.
Automatability0% × 15%
CISA's SSVC Automatable value: no (Vulnrichment).
SSVC (CISA's decision table, applied by EchelonGraph): Track at low, Attend at medium and Act at high mission impact.
Exploitation active (CISA Vulnrichment) · Automatable no (CISA Vulnrichment) · Technical impact total (CISA Vulnrichment). All three are CISA's SSVC values (Vulnrichment). EchelonGraph applied CISA's decision table to them; CISA publishes SSVC inputs and the table, not a decision for each CVE.
Action: A fix is available. Apply it within your standard update timelines at low, sooner than that at medium and as soon as possible at high mission impact.
EPSS PROB
67%
EPSS %ILE
99th
KEV
⚠ Exploited

What the EG score is made of (scorer v4.0: the three questions the 0–10 score mixes, published apart · methodology)

The EG score (9.0): severity, escalated by confirmed exploitation. This CVE's 9.0 is the CISA KEV floor for confirmed exploitation, not an impact rating: its impact severity (EG Severity) is CVSS 7.8 HIGH.

EG Severity
7.8 HIGHCVSS-B, impact only: no KEV listing, EPSS or EG-KEV tier raises it.GitHub Security Advisory CVSS
EG Likelihood
67% within 30 daysSource: FIRST EPSS (model v2026.06.15, score date 2026-11-01). FIRST's exploitation probability, not an EchelonGraph model.
Confirmed exploitation
CISA KEV and EG-KEV Tier 1 (exploited in the wild)Reported apart from the likelihood: an observed fact, not a probability.
EG Priority
SSVC Attend at medium mission impactTrack at low, Attend at medium and Act at high mission impact.CISA BOD 26-04: 3 days & forensic triage if the affected system is publicly exposed; 14 days if it is not.Each input and its source, and whom BOD 26-04 binds: the SSVC and BOD 26-04 blocks below.

SSVC (CISA's decision table, applied by EchelonGraph)Track at low, Attend at medium and Act at high mission impact.

A fix is available. Apply it within your standard update timelines at low, sooner than that at medium and as soon as possible at high mission impact.

Exploitation active (CISA Vulnrichment) · Automatable no (CISA Vulnrichment) · Technical impact total (CISA Vulnrichment). All three are CISA's SSVC values (Vulnrichment). EchelonGraph applied CISA's decision table to them; CISA publishes SSVC inputs and the table, not a decision for each CVE. Mission impact is CISA's Mission & Well-being decision point, and only you can judge it. CISA's table makes it high when Mission Prevalence is Essential — the vulnerable component "directly provides capabilities that constitute at least one MEF for at least one entity" (MEF: mission essential function) — or when Public Well-Being Impact is Irreversible: "multiple fatalities are likely", the cyber-physical system "is likely lost or destroyed", "extreme or serious externalities" are imposed on other parties, or social systems such as elections or the financial grid "are destabilized and potentially collapse". CISA's decision table

BOD 26-04 (CISA's remediation timeline, Table 1)3 days & forensic triage if the affected system is publicly exposed; 14 days if it is not.

The score's inputs: In CISA KEV yes (CISA's KEV catalog) · Automatable no (CISA Vulnrichment) · Technical impact total (CISA Vulnrichment). Whether your system is publicly exposed is yours to answer. BOD 26-04 binds US Federal Civilian Executive Branch agencies; for anyone else it is CISA's published timeline, a reference rather than an obligation. The directive · how EchelonGraph applies it

CISA required action“Apply updates per vendor instructions.”

Quoted verbatim from CISA's Known Exploited Vulnerabilities catalog. CISA directs it at US federal civilian executive branch agencies under Binding Operational Directive (BOD) 26-04, which replaced BOD 22-01 on 10 June 2026; it is not EchelonGraph's advice. CISA's notes: https://nvd.nist.gov/vuln/detail/CVE-2021-36934

Published

July 22, 2021

Last Modified

August 10, 2026

Advisory Details (5)

Auto-updated Oct 26, 2026
⚠️ Actively exploited (CISA KEV, CISA Vulnrichment). Patch available. Sources: microsoft, cert, cisa.
CISA🔴 Active Exploitation

Known Exploited Vulnerabilities Catalog | CISA

Known Exploited Vulnerabilities Catalog | CISA. Listed in CISA Known Exploited Vulnerabilities catalog.

https://www.cisa.gov/known-exploited-vulnerabilities-catalog?field_cve=CVE-2021-36934
CERT

VU#506989 - Microsoft Windows 10 gives unprivileged user access to system32\config files

https://www.kb.cert.org/vuls/id/506989
Microsoft

Security Update Guide - Microsoft Security Response Center

https://portal.msrc.microsoft.com/en-US/security-guidance/advisory/CVE-2021-36934
Microsoft

Security Update Guide - Microsoft Security Response Center

https://msrc.microsoft.com/update-guide/vulnerability/CVE-2021-36934

Vendor Advisories for CVE-2021-36934(2)

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

Weakness Classification(2)

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

Data Freshness Timeline

(refreshed 19× in last 7d / 172× in last 30d)

Each row is a time one of our pipelines fetched, updated or re-scored this CVE. 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. An arrow marks a change the record states ("CVSS v3 → 9.1"); EPSS and GHSA rows show the values recorded at that time, not what changed (EPSS values are rounded; hover one for the exact figures). Most recent first.

Showing the most recent 100 of 1,665 refreshes on record for this CVE.

A repeat, a row identical to one the same pipeline wrote less than 10 seconds earlier, is not a separate refresh and is not counted. None are among the latest 100 rows. The 1,565 oldest rows on record are not shown and were not checked, so the counts can still include repeats.

  1. 2026-11-01 17:28 UTCEG score recompute
  2. 2026-11-01 17:28 UTCVendor advisory
  3. 2026-11-01 17:28 UTCGHSA enrichmentGHSA-x4m2-px5g-5q55 · GitHub severity HIGH · GitHub CVSS 7.8
  4. 2026-11-01 16:29 UTCEPSS rescoreEPSS 67% · 99th percentile
  5. 2026-10-31 16:28 UTCEPSS rescoreEPSS 67% · 99th percentile
  6. 2026-10-31 15:33 UTCEG score recompute
  7. 2026-10-31 15:33 UTCVendor advisory
  8. 2026-10-31 15:33 UTCGHSA enrichmentGHSA-x4m2-px5g-5q55 · GitHub severity HIGH · GitHub CVSS 7.8
  9. 2026-10-30 13:38 UTCEG score recompute
  10. 2026-10-30 13:38 UTCVendor advisory
  11. 2026-10-30 13:38 UTCGHSA enrichmentGHSA-x4m2-px5g-5q55 · GitHub severity HIGH · GitHub CVSS 7.8
  12. 2026-10-29 16:29 UTCEPSS rescoreEPSS 67% · 99th percentile
  13. 2026-10-29 11:42 UTCEG score recompute
  14. 2026-10-29 11:42 UTCGHSA enrichmentGHSA-x4m2-px5g-5q55 · GitHub severity HIGH · GitHub CVSS 7.8
  15. 2026-10-28 09:47 UTCEG score recompute
  16. 2026-10-28 09:47 UTCGHSA enrichmentGHSA-x4m2-px5g-5q55 · GitHub severity HIGH · GitHub CVSS 7.8
  17. 2026-10-27 16:28 UTCEPSS rescoreEPSS 67% · 99th percentile
  18. 2026-10-27 07:52 UTCEG score recompute
  19. 2026-10-27 07:52 UTCGHSA enrichmentGHSA-x4m2-px5g-5q55 · GitHub severity HIGH · GitHub CVSS 7.8
  20. 2026-10-26 05:57 UTCGHSA enrichmentGHSA-x4m2-px5g-5q55 · GitHub severity HIGH · GitHub CVSS 7.8
  21. 2026-10-25 18:25 UTCEG score recompute
  22. 2026-10-25 16:28 UTCEPSS rescoreEPSS 67% · 99th percentile
  23. 2026-10-25 04:01 UTCEG score recompute
  24. 2026-10-25 04:01 UTCVendor advisory
  25. 2026-10-25 04:01 UTCGHSA enrichmentGHSA-x4m2-px5g-5q55 · GitHub severity HIGH · GitHub CVSS 7.8
Show 75 more
  1. 2026-10-24 16:28 UTCEPSS rescoreEPSS 67% · 99th percentile
  2. 2026-10-24 02:06 UTCEG score recompute
  3. 2026-10-24 02:06 UTCGHSA enrichmentGHSA-x4m2-px5g-5q55 · GitHub severity HIGH · GitHub CVSS 7.8
  4. 2026-10-23 16:28 UTCEPSS rescoreEPSS 67% · 99th percentile
  5. 2026-10-23 00:11 UTCEG score recompute
  6. 2026-10-23 00:11 UTCGHSA enrichmentGHSA-x4m2-px5g-5q55 · GitHub severity HIGH · GitHub CVSS 7.8
  7. 2026-10-21 22:13 UTCEG score recompute
  8. 2026-10-21 22:13 UTCVendor advisory
  9. 2026-10-21 22:13 UTCGHSA enrichmentGHSA-x4m2-px5g-5q55 · GitHub severity HIGH · GitHub CVSS 7.8
  10. 2026-10-21 16:28 UTCEPSS rescoreEPSS 67% · 99th percentile
  11. 2026-10-20 20:17 UTCEG score recompute
  12. 2026-10-20 20:17 UTCVendor advisory
  13. 2026-10-20 20:17 UTCGHSA enrichmentGHSA-x4m2-px5g-5q55 · GitHub severity HIGH · GitHub CVSS 7.8
  14. 2026-10-20 16:28 UTCEPSS rescoreEPSS 67% · 99th percentile
  15. 2026-10-19 18:21 UTCEG score recompute
  16. 2026-10-19 18:21 UTCVendor advisory
  17. 2026-10-19 18:21 UTCGHSA enrichmentGHSA-x4m2-px5g-5q55 · GitHub severity HIGH · GitHub CVSS 7.8
  18. 2026-10-19 16:28 UTCEPSS rescoreEPSS 67% · 99th percentile
  19. 2026-10-18 16:26 UTCVendor advisory
  20. 2026-10-18 16:26 UTCGHSA enrichmentGHSA-x4m2-px5g-5q55 · GitHub severity HIGH · GitHub CVSS 7.8
  21. 2026-10-18 08:57 UTCEG score recompute
  22. 2026-10-17 17:26 UTCEG score recompute
  23. 2026-10-17 17:26 UTCVendor advisory
  24. 2026-10-17 17:26 UTCGHSA enrichmentGHSA-x4m2-px5g-5q55 · GitHub severity HIGH · GitHub CVSS 7.8
  25. 2026-10-17 16:29 UTCEPSS rescoreEPSS 67% · 99th percentile
  26. 2026-10-16 16:33 UTCEPSS rescoreEPSS 67% · 99th percentile
  27. 2026-10-16 15:29 UTCEG score recompute
  28. 2026-10-16 15:29 UTCGHSA enrichmentGHSA-x4m2-px5g-5q55 · GitHub severity HIGH · GitHub CVSS 7.8
  29. 2026-10-15 13:32 UTCEG score recompute
  30. 2026-10-15 13:31 UTCGHSA enrichmentGHSA-x4m2-px5g-5q55 · GitHub severity HIGH · GitHub CVSS 7.8
  31. 2026-10-14 16:28 UTCEPSS rescoreEPSS 67% · 99th percentile
  32. 2026-10-14 11:34 UTCEG score recompute
  33. 2026-10-14 11:34 UTCGHSA enrichmentGHSA-x4m2-px5g-5q55 · GitHub severity HIGH · GitHub CVSS 7.8
  34. 2026-10-13 16:28 UTCEPSS rescoreEPSS 67% · 99th percentile
  35. 2026-10-13 09:39 UTCVendor advisory
  36. 2026-10-13 09:38 UTCGHSA enrichmentGHSA-x4m2-px5g-5q55 · GitHub severity HIGH · GitHub CVSS 7.8
  37. 2026-10-12 19:13 UTCEG score recompute
  38. 2026-10-12 07:43 UTCVendor advisory
  39. 2026-10-12 07:43 UTCGHSA enrichmentGHSA-x4m2-px5g-5q55 · GitHub severity HIGH · GitHub CVSS 7.8
  40. 2026-10-12 03:20 UTCVendor advisory
  41. 2026-10-12 03:20 UTCGHSA enrichmentGHSA-x4m2-px5g-5q55 · GitHub severity HIGH · GitHub CVSS 7.8
  42. 2026-10-11 22:54 UTCEG score recompute
  43. 2026-10-11 22:54 UTCVendor advisory
  44. 2026-10-11 22:53 UTCGHSA enrichmentGHSA-x4m2-px5g-5q55 · GitHub severity HIGH · GitHub CVSS 7.8
  45. 2026-10-11 18:28 UTCEG score recompute
  46. 2026-10-11 18:28 UTCVendor advisory
  47. 2026-10-11 18:28 UTCGHSA enrichmentGHSA-x4m2-px5g-5q55 · GitHub severity HIGH · GitHub CVSS 7.8
  48. 2026-10-11 14:04 UTCEG score recompute
  49. 2026-10-11 14:04 UTCVendor advisory
  50. 2026-10-11 14:04 UTCGHSA enrichmentGHSA-x4m2-px5g-5q55 · GitHub severity HIGH · GitHub CVSS 7.8
  51. 2026-10-11 09:42 UTCVendor advisory
  52. 2026-10-11 09:42 UTCGHSA enrichmentGHSA-x4m2-px5g-5q55 · GitHub severity HIGH · GitHub CVSS 7.8
  53. 2026-10-11 05:17 UTCVendor advisory
  54. 2026-10-11 05:17 UTCGHSA enrichmentGHSA-x4m2-px5g-5q55 · GitHub severity HIGH · GitHub CVSS 7.8
  55. 2026-10-11 00:55 UTCVendor advisory
  56. 2026-10-11 00:54 UTCGHSA enrichmentGHSA-x4m2-px5g-5q55 · GitHub severity HIGH · GitHub CVSS 7.8
  57. 2026-10-10 20:30 UTCEG score recompute
  58. 2026-10-10 20:30 UTCVendor advisory
  59. 2026-10-10 20:30 UTCGHSA enrichmentGHSA-x4m2-px5g-5q55 · GitHub severity HIGH · GitHub CVSS 7.8
  60. 2026-10-10 19:56 UTCEPSS rescoreEPSS 67% · 99th percentile
  61. 2026-10-10 16:08 UTCGHSA enrichmentGHSA-x4m2-px5g-5q55 · GitHub severity HIGH · GitHub CVSS 7.8
  62. 2026-10-10 11:42 UTCVendor advisory
  63. 2026-10-10 11:42 UTCGHSA enrichmentGHSA-x4m2-px5g-5q55 · GitHub severity HIGH · GitHub CVSS 7.8
  64. 2026-10-10 07:20 UTCVendor advisory
  65. 2026-10-10 07:20 UTCGHSA enrichmentGHSA-x4m2-px5g-5q55 · GitHub severity HIGH · GitHub CVSS 7.8
  66. 2026-10-10 02:57 UTCVendor advisory
  67. 2026-10-10 02:57 UTCGHSA enrichmentGHSA-x4m2-px5g-5q55 · GitHub severity HIGH · GitHub CVSS 7.8
  68. 2026-10-09 22:34 UTCEG score recompute
  69. 2026-10-09 22:34 UTCVendor advisory
  70. 2026-10-09 22:34 UTCGHSA enrichmentGHSA-x4m2-px5g-5q55 · GitHub severity HIGH · GitHub CVSS 7.8
  71. 2026-10-09 20:04 UTCEPSS rescoreEPSS 67% · 99th percentile
  72. 2026-10-09 18:11 UTCVendor advisory
  73. 2026-10-09 18:11 UTCGHSA enrichmentGHSA-x4m2-px5g-5q55 · GitHub severity HIGH · GitHub CVSS 7.8
  74. 2026-10-09 13:48 UTCVendor advisory
  75. 2026-10-09 13:48 UTCGHSA enrichmentGHSA-x4m2-px5g-5q55 · GitHub severity HIGH · GitHub CVSS 7.8

Publicly available exploits

(11 references, 10 shown)

Public exploit code is referenced for this CVE (1 Metasploit module, 9 GitHub PoCs), as is 1 GitHub checker repository. A GitHub repository named or described as a checker or scanner checks whether a system is affected; it is not necessarily exploit code. Defenders should treat patch urgency accordingly.

  • Metasploitpost/windows/gather/credentials/windows_sam_hivenightmare✓ verified
    Published Jul 29, 2021

    Windows SAM secrets leak - HiveNightmare

    Open source ↗
  • GitHub PoCchron1k/oxide_hive
    Published Aug 12, 2021

    Exploit for CVE-2021-36934

    Open source ↗
  • GitHub PoCexploitblizzard/CVE-2021-36934
    Published Jul 27, 2021

    HiveNightmare aka SeriousSAM

    Open source ↗
  • GitHub PoCSp00kySkelet0n/PyNightmare
    Published Jul 25, 2021

    PoC for CVE-2021-36934 Aka HiveNightmare/SeriousSAM written in python3

    Open source ↗
  • GitHub PoCPreventions/CVE-2021-36934
    Published Jul 24, 2021

    C# PoC for CVE-2021-36934/HiveNightmare/SeriousSAM

    Open source ↗
  • GitHub PoCromarroca/SeriousSam
    Published Jul 22, 2021

    HiveNightmare a.k.a. SeriousSam Local Privilege Escalation in Windows – CVE-2021-36934

    Open source ↗
  • GitHub PoCWh04m1001/VSSCopy
    Published Jul 22, 2021

    Small and dirty PoC for CVE-2021-36934

    Open source ↗
  • GitHub PoCWiredPulse/Invoke-HiveNightmare
    Published Jul 22, 2021

    PoC for CVE-2021-36934, which enables a standard user to be able to retrieve the SAM, Security, and Software Registry hives in Windows 10 version 1809 or newer

    Open source ↗
  • GitHub checkern3tsurge/CVE-2021-36934
    Published Jul 21, 2021

    Detection and Mitigation script for CVE-2021-36934 (HiveNightmare aka. SeriousSam)

    Open source ↗
  • GitHub PoCJoranSlingerland/CVE-2021-36934
    Published Jul 21, 2021

    Fix for the CVE-2021-36934

    Open source ↗

Frequently asked(6)

What is CVE-2021-36934?
CVE-2021-36934 is a critical-severity vulnerability; its CVE record was published on July 22, 2021. An elevation of privilege vulnerability exists because of overly permissive Access Control Lists (ACLs) on multiple system files, including the Security Accounts Manager (SAM) database. An attacker who successfully exploited this vulnerability could run arbitrary code with SYSTEM privileges. An…
When was CVE-2021-36934 made public?
CVE-2021-36934 was made public on July 20, 2021: that is the date its CVE record's CNA, Microsoft Corporation, gives for when the vulnerability was made public. The CVE record itself was published on July 22, 2021. EchelonGraph's copy of the record carries a last-modified date of August 10, 2026; the record at its source may have been updated since.
Is CVE-2021-36934 actively exploited?
Yes. CISA added CVE-2021-36934 to the Known Exploited Vulnerabilities catalog on February 10, 2022, affecting Microsoft Windows. KEV listing indicates confirmed exploitation in the wild; this CVE warrants immediate attention. A fix is available. Apply it.
What is the CVSS score of CVE-2021-36934?
CVE-2021-36934 has a CVSS v3 base score of 7.8 (NVD). EchelonGraph synthesises NVD + CISA KEV + FIRST EPSS + GHSA into a combined EG score of 9.0 (CRITICAL).
Which products are affected by CVE-2021-36934?
CVE-2021-36934 affects Microsoft Windows.
How do I remediate CVE-2021-36934?
A fix for CVE-2021-36934 is available: update to the fixed version the vendor names in its advisory. The vendor advisories EchelonGraph has for CVE-2021-36934 are linked in the Vendor Advisories panel on this page.

Dependency Blast Radius

Explore the affected products and dependency analysis for CVE-2021-36934

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