How severe is CVE-2021-20873?

CVE-2021-20873 has a CVSS 3.x base score of 8.1, rated high severity. It is exploitable over network with low attack complexity, requires no privileges and user interaction. Impact on confidentiality is high, integrity high, and availability none.

Is CVE-2021-20873 being actively exploited?

It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 1% (54th percentile), an estimate of the probability of exploitation in the next 30 days.

What products are affected by CVE-2021-20873?

CVE-2021-20873 affects Yappli. See the affected-products list for the exact vulnerable versions.

How do I fix CVE-2021-20873?

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

When was CVE-2021-20873 published?

CVE-2021-20873 was published on 2021-12-28 and last updated on 2026-06-17.

CVE-2021-20873

CVE-2021-20873 is a high-severity vulnerability in Yappli with a CVSS 3.x base score of 8.1. 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-862.

Key facts

Severity: High (CVSS 3.x base score 8.1)
CVSS v2: 5.8
EPSS exploit prediction: 1% (54th percentile)
Actively exploited: Not listed in CISA KEV
Weakness: CWE-862
Affected product: Yappli
Published: 2021-12-28
Last modified: 2026-06-17

Description

Yappli is an application development platform which provides the function to access a requested URL using Custom URL Scheme. When Android apps are developed with Yappli versions since v7.3.6 and prior to v9.30.0, they are vulnerable to improper authorization in Custom URL Scheme handler, and may be directed to unintended sites via a specially crafted URL.

Frequently asked questions

What is CVE-2021-20873?: Yappli is an application development platform which provides the function to access a requested URL using Custom URL Scheme. When Android apps are developed with Yappli versions since v7.3.6 and prior to v9.30.0, they are vulnerable to improper authorization in Custom URL Scheme handler, and may be directed to unintended sites via a specially crafted URL.
How severe is CVE-2021-20873?: CVE-2021-20873 has a CVSS 3.x base score of 8.1, rated high severity. It is exploitable over network with low attack complexity, requires no privileges and user interaction. Impact on confidentiality is high, integrity high, and availability none.
Is CVE-2021-20873 being actively exploited?: It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 1% (54th percentile), an estimate of the probability of exploitation in the next 30 days.
What products are affected by CVE-2021-20873?: CVE-2021-20873 affects Yappli. See the affected-products list for the exact vulnerable versions.
How do I fix CVE-2021-20873?: Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround. Given its high severity, prioritise patching exposed systems.
When was CVE-2021-20873 published?: CVE-2021-20873 was published on 2021-12-28 and last updated on 2026-06-17.

References

Affected products (1)

cpe:2.3:a:yappli:yappli:*:*:*:*:*:*:*:*

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