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CVE Record

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 th...

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.

UnknownCVSS not scoredNot KEV-listedUpdated
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Glexia's TakeAutomated analysismoderate

Security readout for executives and security teams

Plain-English summary

CVE-2018-8899 is a cross-site scripting risk in IdentityServer4 authorization response pages. In affected versions, the redirect URI was not encoded before display. If a deployment exposes the vulnerable page in a susceptible configuration, a user-facing identity flow could render attacker-controlled content.

Executive priority

Treat this as a targeted identity-platform maintenance issue, not an emergency based on current evidence. Prioritize remediation for internet-facing login systems or shared identity services because XSS in authentication flows can damage trust and user safety.

Technical view

IdentityServer4 1.x before 1.5.3 and 2.x before 2.1.3 did not encode the redirect URI on the authorization response page. The CVE states this might lead to XSS in some configurations. The referenced releases and commit indicate fixed versions are available.

Likely exposure

Exposure is likely limited to applications running IdentityServer4 1.x below 1.5.3 or 2.x below 2.1.3, especially where authorization response pages render redirect URI values. The CVE does not identify other products or platforms.

Exploitation context

The source bundle provides no evidence of active exploitation, and CISA KEV status is false. The risk is conditional: XSS may occur in some configurations where redirect URI content reaches the authorization response page without proper encoding.

Researcher notes

The public data is sparse: no CVSS, CWE, exploitation detail, or configuration matrix is included. Analysis should stay anchored to version exposure and redirect URI encoding on the authorization response page. Avoid assuming exploitability without confirming local rendering behavior.

Mitigation direction

  • Upgrade IdentityServer4 1.x deployments to at least 1.5.3.
  • Upgrade IdentityServer4 2.x deployments to at least 2.1.3.
  • Review vendor release notes and the fixing commit for implementation context.
  • Check custom forks or overrides for unencoded redirect URI rendering.

Validation and detection

  • Inventory IdentityServer4 package versions across applications and build manifests.
  • Confirm no deployed version is below 1.5.3 on 1.x or 2.1.3 on 2.x.
  • Review authorization response page templates for encoded redirect URI output.
  • Verify dependency lockfiles and deployed artifacts match the remediated versions.
Prepared
Confidence
medium
Sources
6

Public sources used

Generated from the cited source records. This long-tail analysis has not been individually reviewed by a named human.

Potential ATT&CK relevance

Conservative CVE-to-ATT&CK context

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CVE-2018-8899 mapping review

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Vulnerability profileCVE Program record
Severity
Unknown
CVSS
Not scored
Known Exploited
No
Published
Official CVE source material

CNA and ADP enrichment extracted from CVE v5

These fields come from the CVE record and ADP containers, not from Glexia's Take. They preserve time-varying source decisions such as CISA SSVC, KEV status, CVSS metrics, and provider references.

0CVSS vectors
0Timeline events
0ADP providers
5Source links

CVSS and timeline data

No CVSS vectors or timeline events were available in the normalized CVE source material.

Source materials

Affected products

Products and packages named in the record

VendorProductVersion / packageStatus
n/an/an/aListed
Weakness

CWE details

No CWE listed

CWE links open Glexia weakness intelligence pages with official CWE context, developer remediation guidance, and related CVE mappings.