Vulnerability-Lookup

CVE-2026-55834 (GCVE-0-2026-55834)

Vulnerability from cvelistv5 – Published: 2026-08-28 16:27 – Updated: 2026-08-28 20:28

Title

Pocket ID: Open Redirect on the OIDC /authorize page via unvalidated redirect_uri with prompt=none

Summary

Pocket ID is an OIDC provider that allows users to authenticate with their passkeys to services. From 2.6.0 until 2.9.0, frontend/src/routes/authorize/+page.ts reads the redirect_uri query parameter and frontend/src/routes/authorize/+page.svelte uses the raw callbackURL in redirectWithError when prompt=none cannot complete silent authorization. The client-side path only blocks javascript and data schemes and does not invoke the backend callback allow-list validation, so an unauthenticated attacker who knows a valid client_id can redirect a victim browser to an arbitrary HTTP or HTTPS origin for phishing or OIDC error and state smuggling. This issue is fixed in version 2.9.0.

Severity

4.3 (Medium)


                        
                          CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:L/A:N

SSVC

Exploitation: poc Automatable: no Technical Impact: partial

CISA Coordinator · CISA-ADP (v2.0.3)

Decision recorded 2026-08-28 20:27 UTC

CWE

CWE-601 - URL Redirection to Untrusted Site ('Open Redirect')

Assigner

GitHub_M mitre root

References

3 references

URL	Tags
https://github.com/pocket-id/pocket-id/security/a…	x_refsource_CONFIRM
https://github.com/pocket-id/pocket-id/commit/8a7…	x_refsource_MISC
https://github.com/pocket-id/pocket-id/releases/t…	x_refsource_MISC

Impacted products

1 product

Vendor	Product	Version	CPE status
pocket-id	pocket-id	Affected: >= 2.6.0, < 2.9.0	guessed

Show details on NVD website

JSON

To clipboard

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FKIE_CVE-2026-55834

Vulnerability from fkie_nvd - Published: 2026-08-28 20:18 - Updated: 2026-08-28 22:16

Severity

4.3 (Medium) - CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:L/A:N

Summary

References

	URL	Tags
	security-advisories@github.com	https://github.com/pocket-id/pocket-id/commit/8a7577497131229badb35cb4b3a4227b1300afff
	security-advisories@github.com	https://github.com/pocket-id/pocket-id/releases/tag/v2.9.0
	security-advisories@github.com	https://github.com/pocket-id/pocket-id/security/advisories/GHSA-2wvm-8mvp-22qv
	134c704f-9b21-4f2e-91b3-4a467353bcc0	https://github.com/pocket-id/pocket-id/security/advisories/GHSA-2wvm-8mvp-22qv

Impacted products

	Vendor	Product	Version

JSON

To clipboard

{
  "affected": [
    {
      "affectedData": [
        {
          "product": "pocket-id",
          "vendor": "pocket-id",
          "versions": [
            {
              "status": "affected",
              "version": "\u003e= 2.6.0, \u003c 2.9.0"
            }
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      ],
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    }
  ],
  "id": "CVE-2026-55834",
  "lastModified": "2026-08-28T22:16:51.850",
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          "confidentialityImpact": "NONE",
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          "privilegesRequired": "NONE",
          "scope": "UNCHANGED",
          "userInteraction": "REQUIRED",
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        "type": "Secondary"
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GHSA-2WVM-8MVP-22QV

Vulnerability from github – Published: 2026-08-28 16:28 – Updated: 2026-08-28 16:28

Summary

Pocket-ID has an Open Redirect on the OIDC /authorize page via unvalidated redirect_uri with prompt=none

Details

Summary

The OIDC authorization page in the pocket-id frontend redirects the browser to an attacker-controlled URL without consulting the backend redirect_uri allow-list when the request uses prompt=none. An attacker who knows a valid client_id can craft an /authorize link that sends a victim (or a victim's browser doing a silent re-auth) to any external https URL, enabling phishing and OAuth response smuggling. The backend allow-list validation that protects the normal authenticated flow is bypassed because this path is handled entirely client-side.

Details

For an OIDC authorization request with prompt=none, the SvelteKit frontend short-circuits the flow before the backend ever validates the redirect_uri against the client's registered callback list.

File: frontend/src/routes/authorize/+page.ts (line 14) parses the raw redirect_uri query parameter from the incoming URL.

File: frontend/src/routes/authorize/+page.svelte - in onMount(), when the request carries prompt=none and the user cannot be silently authorized (for example the visitor is not logged in, so login_required must be returned), the page builds the callback URL from the raw redirect_uri and performs:

window.location.href = `${callbackURL}?error=login_required...`

The callbackURL is taken directly from the user-supplied redirect_uri. The only filtering applied is a scheme check that blocks javascript: and data: URLs; any http: or https: origin passes through. The backend allow-list validator GetCallbackURLFromList (which the authenticated code path uses to confirm the redirect_uri matches one of the client's registered callback URLs) is never invoked on this branch.

This means the per-client redirect_uri allow-list, the central control that makes redirect_uri safe in OAuth/OIDC, is not enforced for the prompt=none error-return path. A client_id is not a secret: client metadata is retrievable at /api/oidc/clients/:id/meta, and client_ids appear in any integration's authorization links.

Confirmation that the bypass is purely frontend: an unauthenticated POST to the backend /api/oidc/authorize endpoint correctly returns 401 ({"error":"You are not signed in"}), so the backend never authorizes the request. The redirect nonetheless happens in the browser because +page.svelte issues window.location.href before/without a successful backend authorization.

A second variant exists for an authenticated victim: when prompt=none is combined with a first-time (not yet consented) authorization of a client, the same client-side path can be reached.

Contrast: the standard interactive flow (no prompt=none) posts to the backend, which validates redirect_uri against the registered list before returning a callback. The defect is specific to the client-side prompt=none short-circuit.

PoC

Prerequisites: a running pocket-id instance, a registered OIDC client whose client_id is known to the attacker (obtainable from /api/oidc/clients/:id/meta or any existing integration), and a victim whose browser opens the link (the victim need not be logged in for the login_required branch).

Attacker constructs an authorization URL pointing at the victim's pocket-id, supplying an external redirect_uri and prompt=none:

https://idp.victim.example/authorize?client_id=&redirect_uri=https://attacker.example/collect&response_type=code&scope=openid&prompt=none

Victim opens the link. The frontend authorize page loads, determines the silent auth cannot succeed (login_required), and executes:

window.location.href = "https://attacker.example/collect?error=login_required&state=..."

The browser is redirected to https://attacker.example/collect. Expected result on a fixed build: the page would refuse the redirect because redirect_uri does not match the client's registered callback list and would render an error in place instead of navigating off-origin.

Validation level: code-level confirmation at commit fc42f62. This is a browser-side window.location.href redirect, so it is not reproducible with curl; the backend was confirmed to reject the unauthenticated request (401) while the frontend performs the navigation regardless. Evidence notes saved to screenshots/001_open_redirect_evidence.txt.

Impact

Unauthenticated attacker, victim interaction required (clicking or being silently redirected). The trusted pocket-id domain is used to bounce a victim to an arbitrary external site, which is effective for credential phishing (the user trusts the IdP origin in the initial link) and for leaking OIDC error/state parameters to an attacker endpoint. Integrity impact is limited to redirection; no confidentiality or availability loss of pocket-id itself. Note: an abandoned PR (#1450) addressed a related protocol-relative URL issue in a different email-redirect path but was not merged and does not cover this authorize-page path.

Severity

4.3 (Medium)


                  
                    CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:L/A:N

Show details on source website

JSON

To clipboard

{
  "affected": [
    {
      "database_specific": {
        "last_known_affected_version_range": "\u003c= 2.8.0"
      },
      "package": {
        "ecosystem": "Go",
        "name": "github.com/pocket-id/pocket-id/backend"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "2.6.0"
            },
            {
              "fixed": "2.9.0"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ]
    }
  ],
  "aliases": [
    "CVE-2026-55834"
  ],
  "database_specific": {
    "cwe_ids": [
      "CWE-601"
    ],
    "github_reviewed": true,
    "github_reviewed_at": "2026-08-28T16:28:20Z",
    "nvd_published_at": null,
    "severity": "MODERATE"
  },
  "details": "### Summary\nThe OIDC authorization page in the pocket-id frontend redirects the browser to an attacker-controlled URL without consulting the backend redirect_uri allow-list when the request uses prompt=none. An attacker who knows a valid client_id can craft an /authorize link that sends a victim (or a victim\u0027s browser doing a silent re-auth) to any external https URL, enabling phishing and OAuth response smuggling. The backend allow-list validation that protects the normal authenticated flow is bypassed because this path is handled entirely client-side.\n\n### Details\nFor an OIDC authorization request with prompt=none, the SvelteKit frontend short-circuits the flow before the backend ever validates the redirect_uri against the client\u0027s registered callback list.\n\nFile: frontend/src/routes/authorize/+page.ts (line 14) parses the raw redirect_uri query parameter from the incoming URL.\n\nFile: frontend/src/routes/authorize/+page.svelte - in onMount(), when the request carries prompt=none and the user cannot be silently authorized (for example the visitor is not logged in, so login_required must be returned), the page builds the callback URL from the raw redirect_uri and performs:\n\n    window.location.href = `${callbackURL}?error=login_required...`\n\nThe callbackURL is taken directly from the user-supplied redirect_uri. The only filtering applied is a scheme check that blocks javascript: and data: URLs; any http: or https: origin passes through. The backend allow-list validator GetCallbackURLFromList (which the authenticated code path uses to confirm the redirect_uri matches one of the client\u0027s registered callback URLs) is never invoked on this branch.\n\nThis means the per-client redirect_uri allow-list, the central control that makes redirect_uri safe in OAuth/OIDC, is not enforced for the prompt=none error-return path. A client_id is not a secret: client metadata is retrievable at /api/oidc/clients/:id/meta, and client_ids appear in any integration\u0027s authorization links.\n\nConfirmation that the bypass is purely frontend: an unauthenticated POST to the backend /api/oidc/authorize endpoint correctly returns 401 ({\"error\":\"You are not signed in\"}), so the backend never authorizes the request. The redirect nonetheless happens in the browser because +page.svelte issues window.location.href before/without a successful backend authorization.\n\nA second variant exists for an authenticated victim: when prompt=none is combined with a first-time (not yet consented) authorization of a client, the same client-side path can be reached.\n\nContrast: the standard interactive flow (no prompt=none) posts to the backend, which validates redirect_uri against the registered list before returning a callback. The defect is specific to the client-side prompt=none short-circuit.\n\n### PoC\nPrerequisites: a running pocket-id instance, a registered OIDC client whose client_id is known to the attacker (obtainable from /api/oidc/clients/:id/meta or any existing integration), and a victim whose browser opens the link (the victim need not be logged in for the login_required branch).\n\n1. Attacker constructs an authorization URL pointing at the victim\u0027s pocket-id, supplying an external redirect_uri and prompt=none:\n\n   https://idp.victim.example/authorize?client_id=\u003cknown_client_id\u003e\u0026redirect_uri=https://attacker.example/collect\u0026response_type=code\u0026scope=openid\u0026prompt=none\n\n2. Victim opens the link. The frontend authorize page loads, determines the silent auth cannot succeed (login_required), and executes:\n\n   window.location.href = \"https://attacker.example/collect?error=login_required\u0026state=...\"\n\n3. The browser is redirected to https://attacker.example/collect. Expected result on a fixed build: the page would refuse the redirect because redirect_uri does not match the client\u0027s registered callback list and would render an error in place instead of navigating off-origin.\n\nValidation level: code-level confirmation at commit fc42f62. This is a browser-side window.location.href redirect, so it is not reproducible with curl; the backend was confirmed to reject the unauthenticated request (401) while the frontend performs the navigation regardless. Evidence notes saved to screenshots/001_open_redirect_evidence.txt.\n\n### Impact\nUnauthenticated attacker, victim interaction required (clicking or being silently redirected). The trusted pocket-id domain is used to bounce a victim to an arbitrary external site, which is effective for credential phishing (the user trusts the IdP origin in the initial link) and for leaking OIDC error/state parameters to an attacker endpoint. Integrity impact is limited to redirection; no confidentiality or availability loss of pocket-id itself. Note: an abandoned PR (#1450) addressed a related protocol-relative URL issue in a different email-redirect path but was not merged and does not cover this authorize-page path.",
  "id": "GHSA-2wvm-8mvp-22qv",
  "modified": "2026-08-28T16:28:20Z",
  "published": "2026-08-28T16:28:20Z",
  "references": [
    {
      "type": "WEB",
      "url": "https://github.com/pocket-id/pocket-id/security/advisories/GHSA-2wvm-8mvp-22qv"
    },
    {
      "type": "WEB",
      "url": "https://github.com/pocket-id/pocket-id/commit/8a7577497131229badb35cb4b3a4227b1300afff"
    },
    {
      "type": "PACKAGE",
      "url": "https://github.com/pocket-id/pocket-id"
    },
    {
      "type": "WEB",
      "url": "https://github.com/pocket-id/pocket-id/releases/tag/v2.9.0"
    }
  ],
  "schema_version": "1.4.0",
  "severity": [
    {
      "score": "CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:L/A:N",
      "type": "CVSS_V3"
    }
  ],
  "summary": "Pocket-ID has an Open Redirect on the OIDC /authorize page via unvalidated redirect_uri with prompt=none"
}

Sightings

Author	Source	Type	Date	Other

Nomenclature

Seen: The vulnerability was mentioned, discussed, or observed by the user.
Confirmed: The vulnerability has been validated from an analyst's perspective.
Published Proof of Concept: A public proof of concept is available for this vulnerability.
Exploited: The vulnerability was observed as exploited by the user who reported the sighting.
Patched: The vulnerability was observed as successfully patched by the user who reported the sighting.
Not exploited: The vulnerability was not observed as exploited by the user who reported the sighting.
Not confirmed: The user expressed doubt about the validity of the vulnerability.
Not patched: The vulnerability was not observed as successfully patched by the user who reported the sighting.

Detection rules are retrieved from Rulezet.

The MITRE ATT&CK techniques below are AI-generated suggestions, inferred from the description of the vulnerability by the CIRCL/vulnerability-attack-technique-classification-roberta-base model, served locally by ML-Gateway. They have not been verified by an analyst and are provided for guidance only.
The approach is described in our paper Mapping CVEs to MITRE ATT&CK Techniques: A Curated Gold-Set Classifier and the Limits of LLM-Assisted Label Expansion.

Action not permitted

CVE-2026-55834 (GCVE-0-2026-55834)

FKIE_CVE-2026-55834

GHSA-2WVM-8MVP-22QV

Summary

Details

PoC

Impact

Tags

Sightings

Nomenclature