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Medium, CVSS 5.1

IdentityServer Open Redirect vulnerability

GHSA-55p7-v223-x366

What to do

Vendor response not established. Follow the primary source's mitigation guidance and check back for a fix.

This page has no inventory attached, so it cannot say whether you are affected. A vendor fix is not proof that your deployment is fixed.

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Affected packages

  • NuGet identityserver4

    Affected
    <= 4.1.2
    Fixed in
    no fixed version recorded

Sources

Severity and exploitation
Exploitation
No confirmed exploitation recorded. Patch Next marks exploitation only from CISA KEV.
CVSS 4.0
5.1 · CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:A/VC:L/VI:N/VA:N/SC:L/SI:N/SA:N · score source
EPSS
No dated EPSS signal available.
Source description

As published by the source; long descriptions are shortened.

Impact It is possible for an attacker to craft malicious Urls that certain functions in IdentityServer will incorrectly treat as local and trusted. If such a Url is returned as a redirect, some browsers will follow it to a third-party, untrusted site. Affected Methods - In the DefaultIdentityServerInteractionService, the GetAuthorizationContextAsync method may return non-null and the IsValidReturnUrl method may return true for malicious Urls, indicating incorrectly that they can be safely redirected to. UI code calling these two methods is the most commonly used code path that will expose the vulnerability. The default UI templates rely on this behavior in the Login, Challenge, and Consent pages. Customized user interface code might also rely on this behavior. The following uncommonly used APIs are also vulnerable: - The ServerUrlExtensions.GetIdentityServerRelativeUrl, ReturnUrlParser.ParseAsync and OidcReturnUrlParser.ParseAsync methods may incorrectly return non-null, and the…

Dates and revisions
Published by the source
Last modified by the source
Source last checked
  1. Revision 1 · created ·

    Published from ghsa record GHSA-55p7-v223-x366

Agent brief

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# Patch Next advisory brief: GHSA-55p7-v223-x366

Advisory: IdentityServer Open Redirect vulnerability
IDs: GHSA-55p7-v223-x366
Record: https://patchnext.com/advisories/ghsa-55p7-v223-x366 (revision 1, source checked 26 Oct 2026, 17:00 UTC)
Inventory: none attached. This brief comes from a public page and does not say whether any deployment is affected.
Severity: Medium (CVSS 5.1)
Exploitation: no confirmed exploitation recorded. Patch Next confirms exploitation only from CISA KEV.
Vendor response: Vendor response not established. A vendor fix does not mean a deployment is fixed.

## Affected components
- NuGet identityserver4: affected <= 4.1.2

## Suggested inspection (read-only)
- NuGet identityserver4: check the installed version with your package manager.

## Supported action
No complete vendor fix is recorded. Follow the primary source's mitigation guidance and check this record again before closing anything.

## Required regression checks
- Run the test suite and a production build.
- Exercise the features that depend on identityserver4.
- Repeat the inspection and confirm that only fixed versions remain installed.

## Rollback considerations
- Keep the previous lockfile and deployment artifact. Rolling back reinstates the vulnerable version, so apply any documented mitigation while you fix forward.

## Unresolved questions
- Which deployments run an affected version?
- Exploitation status can change. Check again before lowering the priority.
- Mark the work resolved only after the fixed version is verified in production.

## Sources
- Verified: https://github.com/advisories/GHSA-55p7-v223-x366 (GitHub-reviewed advisory GHSA-55p7-v223-x366 lists affected ranges: NuGet identityserver4 >=0 <=4.1.2)

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