CVE-2021-39392

CRITICALNVD 9.89.8—
EchelonGraph scoreMEDIUM confidence

This critical-severity CVE scores 9.8 under NVD CVSS v3. EPSS exploit probability: 2.3%, top 19% of all CVEs by exploit prediction. GitHub Security Advisory data not yet ingested — confidence will rise once GHSA publishes (typical lag: hours to days for open-source ecosystem CVEs; never for infrastructure-only CVEs).

Triggered by: NVD CVSS baseline
Sources: epss, nvd
9.8
EchelonGraph verdictPlan a fixSerious severity, but no confirmed exploitation yet.
  • High severity, but no confirmed exploitation yet
CISA-KEV: Not listedEPSS: 2%CVSS: 9.8Exploit: NoneExposed: 0

No vendor fix yet — apply a workaround or compensating control (WAF / firewall / segmentation) and watch for a patch.

The management tool in MyLittleBackup up to and including 1.7 allows remote attackers to execute arbitrary code because machineKey is hardcoded (the same for all customers' installations) in web.config, and can be used to send serialized ASP code.

CVSS v3
9.8
EG Score
9.8(medium)
EG Risk
50(Track)
EG Risk 50/100SSVC: 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%
Exploitation2% × 40%
Automatability30% × 15%
Action: Routine — remediate on your standard cadence.
EPSS
81.1%
KEV
Not listed

Published

September 15, 2021

Last Modified

November 21, 2024

Advisory Details (1)

Auto-updated Jul 12, 2026
No patch confirmed yet.
generic

MyLittleBackup Vulnerability · GitHub

https://gist.github.com/omriinbar/65827626e63f15e3e50557e2d9d61281

Weakness Classification(1)

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

Data Freshness Timeline

(refreshed 11× in last 7d / 45× 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.

  1. 2026-07-23 14:16 UTCEPSS rescore
  2. 2026-07-23 02:04 UTCEG score recompute
  3. 2026-07-22 22:50 UTCEG score recompute
  4. 2026-07-22 14:06 UTCEPSS rescore
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  1. 2026-07-07 13:43 UTCEPSS rescore
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  69. 2026-05-26 10:20 UTCEG score recompute
  70. 2026-05-26 10:20 UTCGHSA enrichment
  71. 2026-05-26 07:17 UTCEPSS rescore
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Frequently asked(5)

What is CVE-2021-39392?
CVE-2021-39392 is a critical vulnerability published on September 15, 2021. The management tool in MyLittleBackup up to and including 1.7 allows remote attackers to execute arbitrary code because machineKey is hardcoded (the same for all customers' installations) in web.config, and can be used to send serialized ASP code.
When was CVE-2021-39392 disclosed?
CVE-2021-39392 was first published in the National Vulnerability Database on September 15, 2021, with the most recent update on November 21, 2024. EchelonGraph re-ingests CVE updates from NVD on a 2-hour cycle, so this page reflects the latest published state.
Is CVE-2021-39392 actively exploited?
CVE-2021-39392 is not currently on CISA's Known Exploited Vulnerabilities catalog. FIRST EPSS estimates a 81.1% percentile likelihood of exploitation in the next 30 days — higher percentiles indicate greater predicted risk.
What is the CVSS score of CVE-2021-39392?
CVE-2021-39392 has a CVSS v3 base score of 9.8 (NVD).
How do I remediate CVE-2021-39392?
Patch to the fixed version published by the affected vendor. Where vendor advisories exist for CVE-2021-39392, 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.

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