How severe is CVE-2021-3977?

CVE-2021-3977 has a CVSS 3.x base score of 5.4, rated medium severity. It is exploitable over network with low attack complexity, requires low privileges and user interaction. Impact on confidentiality is low, integrity low, and availability none.

Is CVE-2021-3977 being actively exploited?

It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 1% (44th percentile), an estimate of the probability of exploitation in the next 30 days.

What products are affected by CVE-2021-3977?

CVE-2021-3977 affects Invoiceninja Invoice Ninja. See the affected-products list for the exact vulnerable versions.

How do I fix CVE-2021-3977?

Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround.

When was CVE-2021-3977 published?

CVE-2021-3977 was published on 2021-12-24 and last updated on 2026-06-17.

CVE-2021-3977

CVE-2021-3977 is a medium-severity vulnerability in Invoiceninja Invoice Ninja with a CVSS 3.x base score of 5.4. 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-79.

Key facts

Severity: Medium (CVSS 3.x base score 5.4)
CVSS v2: 3.5
EPSS exploit prediction: 1% (44th percentile)
Actively exploited: Not listed in CISA KEV
Weakness: CWE-79
Affected product: Invoiceninja Invoice Ninja
Published: 2021-12-24
Last modified: 2026-06-17

Description

invoiceninja is vulnerable to Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting')

Frequently asked questions

What is CVE-2021-3977?: invoiceninja is vulnerable to Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting')
How severe is CVE-2021-3977?: CVE-2021-3977 has a CVSS 3.x base score of 5.4, rated medium severity. It is exploitable over network with low attack complexity, requires low privileges and user interaction. Impact on confidentiality is low, integrity low, and availability none.
Is CVE-2021-3977 being actively exploited?: It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 1% (44th percentile), an estimate of the probability of exploitation in the next 30 days.
What products are affected by CVE-2021-3977?: CVE-2021-3977 affects Invoiceninja Invoice Ninja. See the affected-products list for the exact vulnerable versions.
How do I fix CVE-2021-3977?: Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround.
When was CVE-2021-3977 published?: CVE-2021-3977 was published on 2021-12-24 and last updated on 2026-06-17.

References

Affected products (1)

cpe:2.3:a:invoiceninja:invoice_ninja:*:*:*:*:*:*:*:*

More vulnerabilities in Invoiceninja Invoice Ninja

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CVE-2026-33628 — Medium (CVSS 5.4): Invoice Ninja is a source-available invoice, quote, project and time-tracking app built with Laravel. Invoice line item…
CVE-2017-1000466 — Medium (CVSS 5.4): Invoice Ninja version 3.8.1 is vulnerable to stored cross-site scripting vulnerability, within the invoice creation…

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