How severe is CVE-2021-42770?

CVE-2021-42770 has a CVSS 3.x base score of 6.1, rated medium severity. It is exploitable over network with low attack complexity, requires no privileges and user interaction. Impact on confidentiality is low, integrity low, and availability none.

Is CVE-2021-42770 being actively exploited?

It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 1% (68th percentile), an estimate of the probability of exploitation in the next 30 days.

What products are affected by CVE-2021-42770?

CVE-2021-42770 affects Opnsense. See the affected-products list for the exact vulnerable versions.

How do I fix CVE-2021-42770?

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

When was CVE-2021-42770 published?

CVE-2021-42770 was published on 2021-11-08 and last updated on 2026-06-17.

CVE-2021-42770

CVE-2021-42770 is a medium-severity vulnerability in Opnsense with a CVSS 3.x base score of 6.1. 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 6.1)
CVSS v2: 4.3
EPSS exploit prediction: 1% (68th percentile)
Actively exploited: Not listed in CISA KEV
Weakness: CWE-79
Affected product: Opnsense
Published: 2021-11-08
Last modified: 2026-06-17

Description

A Cross-site scripting (XSS) vulnerability was discovered in OPNsense before 21.7.4 via the LDAP attribute return in the authentication tester.

Frequently asked questions

What is CVE-2021-42770?: A Cross-site scripting (XSS) vulnerability was discovered in OPNsense before 21.7.4 via the LDAP attribute return in the authentication tester.
How severe is CVE-2021-42770?: CVE-2021-42770 has a CVSS 3.x base score of 6.1, rated medium severity. It is exploitable over network with low attack complexity, requires no privileges and user interaction. Impact on confidentiality is low, integrity low, and availability none.
Is CVE-2021-42770 being actively exploited?: It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 1% (68th percentile), an estimate of the probability of exploitation in the next 30 days.
What products are affected by CVE-2021-42770?: CVE-2021-42770 affects Opnsense. See the affected-products list for the exact vulnerable versions.
How do I fix CVE-2021-42770?: Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround.
When was CVE-2021-42770 published?: CVE-2021-42770 was published on 2021-11-08 and last updated on 2026-06-17.

References

Affected products (1)

cpe:2.3:a:opnsense:opnsense:*:*:*:*:*:*:*:*

More vulnerabilities in Opnsense

CVE-2023-27152 — Critical (CVSS 9.8): DECISO OPNsense 23.1 does not impose rate limits for authentication, allowing attackers to perform a brute-force attack…
CVE-2023-39008 — Critical (CVSS 9.8): A command injection vulnerability in the component /api/cron/settings/setJob/ of OPNsense Community Edition before 23.7…
CVE-2023-39004 — Critical (CVSS 9.8): Insecure permissions in the configuration directory (/conf/) of OPNsense Community Edition before 23.7 and Business…
CVE-2023-39001 — Critical (CVSS 9.8): A command injection vulnerability in the component diag_backup.php of OPNsense Community Edition before 23.7 and…
CVE-2023-39007 — Critical (CVSS 9.6): /ui/cron/item/open in the Cron component of OPNsense Community Edition before 23.7 and Business Edition before 23.4.2…
CVE-2026-45158 — Critical (CVSS 9.1): OPNsense is a FreeBSD based firewall and routing platform. Prior to 26.1.8, unsanitized user input is passed to the…

All CVEs affecting Opnsense →

Other CWE-79 (Cross-site Scripting (XSS)) vulnerabilities

CVE-2025-49410 — Critical (CVSS 10.0): Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting') vulnerability in Imran Emu TC…
CVE-2024-47875 — Critical (CVSS 10.0): DOMPurify is a DOM-only, super-fast, uber-tolerant XSS sanitizer for HTML, MathML and SVG. DOMpurify was vulnerable to…
CVE-2024-6886 — Critical (CVSS 10.0): Improper Neutralization of Input During Web Page Generation (XSS or 'Cross-site Scripting') vulnerability in Gitea…
CVE-2023-45144 — Critical (CVSS 10.0): com.xwiki.identity-oauth:identity-oauth-ui is a package to aid in building identity and service providers based on…
CVE-2023-45138 — Critical (CVSS 10.0): Change Request is an pplication allowing users to request changes on a wiki without publishing the changes directly.…
CVE-2022-4361 — Critical (CVSS 10.0): Keycloak, an open-source identity and access management solution, has a cross-site scripting (XSS) vulnerability in the…

Browse all CWE-79 (Cross-site Scripting (XSS)) vulnerabilities →