How severe is CVE-2021-39392?

CVE-2021-39392 has a CVSS 3.x base score of 9.8, rated critical severity. It is exploitable over network with low attack complexity, requires no privileges and no user interaction. Impact on confidentiality is high, integrity high, and availability high.

Is CVE-2021-39392 being actively exploited?

It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 2% (80th percentile), an estimate of the probability of exploitation in the next 30 days.

What products are affected by CVE-2021-39392?

CVE-2021-39392 affects Mylittletools Mylittlebackup. See the affected-products list for the exact vulnerable versions.

How do I fix CVE-2021-39392?

Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround. Given its critical severity, prioritise patching exposed systems.

When was CVE-2021-39392 published?

CVE-2021-39392 was published on 2021-09-15 and last updated on 2026-06-17.

CVE-2021-39392

CVE-2021-39392 is a critical-severity vulnerability in Mylittletools Mylittlebackup with a CVSS 3.x base score of 9.8. It is not currently listed as actively exploited by CISA, and its EPSS exploit-prediction score is low. The underlying weakness is classified as CWE-502.

Key facts

Severity: Critical (CVSS 3.x base score 9.8)
CVSS v2: 7.5
EPSS exploit prediction: 2% (80th percentile)
Actively exploited: Not listed in CISA KEV
Weakness: CWE-502
Affected product: Mylittletools Mylittlebackup
Published: 2021-09-15
Last modified: 2026-06-17

Description

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.

Frequently asked questions

What is CVE-2021-39392?: 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.
How severe is CVE-2021-39392?: CVE-2021-39392 has a CVSS 3.x base score of 9.8, rated critical severity. It is exploitable over network with low attack complexity, requires no privileges and no user interaction. Impact on confidentiality is high, integrity high, and availability high.
Is CVE-2021-39392 being actively exploited?: It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 2% (80th percentile), an estimate of the probability of exploitation in the next 30 days.
What products are affected by CVE-2021-39392?: CVE-2021-39392 affects Mylittletools Mylittlebackup. See the affected-products list for the exact vulnerable versions.
How do I fix CVE-2021-39392?: Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround. Given its critical severity, prioritise patching exposed systems.
When was CVE-2021-39392 published?: CVE-2021-39392 was published on 2021-09-15 and last updated on 2026-06-17.

References

Affected products (1)

cpe:2.3:a:mylittletools:mylittlebackup:*:*:*:*:*:*:*:*

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