How severe is CVE-2018-8899?

CVE-2018-8899 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-2018-8899 being actively exploited?

It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 1% (66th percentile), an estimate of the probability of exploitation in the next 30 days.

What products are affected by CVE-2018-8899?

CVE-2018-8899 affects Identityserver Identityserver4. See the affected-products list for the exact vulnerable versions.

How do I fix CVE-2018-8899?

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

When was CVE-2018-8899 published?

CVE-2018-8899 was published on 2018-03-22 and last updated on 2026-06-17.

CVE-2018-8899

CVE-2018-8899 is a medium-severity vulnerability in Identityserver Identityserver4 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% (66th percentile)
Actively exploited: Not listed in CISA KEV
Weakness: CWE-79
Affected product: Identityserver Identityserver4
Published: 2018-03-22
Last modified: 2026-06-17

Description

IdentityServer IdentityServer4 1.x before 1.5.3 and 2.x before 2.1.3 does not encode the redirect URI on the authorization response page, which might lead to XSS in some configurations.

Frequently asked questions

What is CVE-2018-8899?: IdentityServer IdentityServer4 1.x before 1.5.3 and 2.x before 2.1.3 does not encode the redirect URI on the authorization response page, which might lead to XSS in some configurations.
How severe is CVE-2018-8899?: CVE-2018-8899 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-2018-8899 being actively exploited?: It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 1% (66th percentile), an estimate of the probability of exploitation in the next 30 days.
What products are affected by CVE-2018-8899?: CVE-2018-8899 affects Identityserver Identityserver4. See the affected-products list for the exact vulnerable versions.
How do I fix CVE-2018-8899?: Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround.
When was CVE-2018-8899 published?: CVE-2018-8899 was published on 2018-03-22 and last updated on 2026-06-17.

References

Affected products (1)

cpe:2.3:a:identityserver:identityserver4:*:*:*:*:*:*:*:*

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