GHSA-MRX3-GXJX-HJQJ

Vulnerability from github – Published: 2024-01-29 22:30 – Updated: 2024-11-18 16:26
VLAI
Summary
Authentik vulnerable to PKCE downgrade attack
Details

Summary

PKCE is a very important countermeasure in OAuth2 , both for public and confidential clients. It protects against CSRF attacks and code injection attacks. Because of this bug, an attacker can circumvent the protection PKCE offers.

Patches

authentik 2023.8.7 and 2023.10.7 fix this issue.

Details

There is a bug in our implementation of PKCE that allows an attacker to circumvent the protection that PKCE offers. PKCE adds the code_challenge’ parameter to the authorization request and adds thecode_verifier’ parameter to the token request. We recently fixed a downgrade attack (in v2023.8.5 and 2023.10.4) where if the attacker removed the code_verifier’ parameter in the token request, authentik would allow the request to pass, thus circumventing PKCE’s protection. However, in the latest version of the software, another downgrade scenario is still possible: if the attacker removes thecode_challenge’ parameter from the authorization request, authentik will also not do the PKCE check.

Note that this type of downgrade enables an attacker to perform a code injection attack, even if the OAuth client is using PKCE (which is supposed to protect against code injection attacks). To start the attack, the attacker must initiate the authorization process without that code_challenge’ parameter in the authorization request. But this is easy to do (just use a phishing site or email to trick the user into clicking on a link that the attacker controls – the authorization link without thatcode_challenge’ parameter).

The OAuth BCP (https://datatracker.ietf.org/doc/html/draft-ietf-oauth-security-topics) explicitly mentions this particular attack in section 2.1.1: “Authorization servers MUST mitigate PKCE Downgrade Attacks by ensuring that a token request containing a code_verifier parameter is accepted only if a code_challenge parameter was present in the authorization request, see Section 4.8.2 for details.”

For more information

If you have any questions or comments about this advisory:

Severity
6.5 (Medium)
CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:H/A:N
7.1 (High)
CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:P/VC:N/VI:H/VA:N/SC:N/SI:N/SA:N
Show details on source website
To clipboard 

{
  "affected": [
    {
      "database_specific": {
        "last_known_affected_version_range": "\u003c= 2023.10.6"
      },
      "package": {
        "ecosystem": "Go",
        "name": "goauthentik.io"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "2023.10.0"
            },
            {
              "fixed": "2023.10.7"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ]
    },
    {
      "database_specific": {
        "last_known_affected_version_range": "\u003c= 2023.8.6"
      },
      "package": {
        "ecosystem": "Go",
        "name": "goauthentik.io"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "0"
            },
            {
              "fixed": "2023.8.7"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ]
    }
  ],
  "aliases": [
    "CVE-2024-23647"
  ],
  "database_specific": {
    "cwe_ids": [
      "CWE-287"
    ],
    "github_reviewed": true,
    "github_reviewed_at": "2024-01-29T22:30:54Z",
    "nvd_published_at": "2024-01-30T17:15:10Z",
    "severity": "HIGH"
  },
  "details": "## Summary\n\nPKCE is a very important countermeasure in OAuth2 , both for public and confidential clients. It protects against CSRF attacks and code injection attacks. Because of this bug, an attacker can circumvent the protection PKCE offers.\n\n## Patches\n\nauthentik 2023.8.7 and 2023.10.7 fix this issue.\n\n## Details\n\nThere is a bug in our implementation of PKCE that allows an attacker to circumvent the protection that PKCE offers. PKCE adds the `code_challenge\u2019 parameter to the authorization request and adds the `code_verifier\u2019 parameter to the token request. We recently fixed a downgrade attack (in v2023.8.5 and 2023.10.4) where if the attacker removed the `code_verifier\u2019 parameter in the token request, authentik would allow the request to pass, thus circumventing PKCE\u2019s protection. However, in the latest version of the software, another downgrade scenario is still possible: if the attacker removes the `code_challenge\u2019 parameter from the authorization request, authentik will also not do the PKCE check.\n\nNote that this type of downgrade enables an attacker to perform a code injection attack, even if the OAuth client is using PKCE (which is supposed to protect against code injection attacks). To start the attack, the attacker must initiate the authorization process without that `code_challenge\u2019 parameter in the authorization request. But this is easy to do (just use a phishing site or email to trick the user into clicking on a link that the attacker controls \u2013 the authorization link without that `code_challenge\u2019 parameter).\n\nThe OAuth BCP (https://datatracker.ietf.org/doc/html/draft-ietf-oauth-security-topics) explicitly mentions this particular attack in section 2.1.1: \u201cAuthorization servers MUST mitigate PKCE Downgrade Attacks by ensuring that a token request containing a code_verifier parameter is accepted only if a code_challenge parameter was present in the authorization request, see Section 4.8.2 for details.\u201d\n\n## For more information\n\nIf you have any questions or comments about this advisory:\n\n-   Email us at [security@goauthentik.io](mailto:security@goauthentik.io)\n",
  "id": "GHSA-mrx3-gxjx-hjqj",
  "modified": "2024-11-18T16:26:35Z",
  "published": "2024-01-29T22:30:54Z",
  "references": [
    {
      "type": "WEB",
      "url": "https://github.com/goauthentik/authentik/security/advisories/GHSA-mrx3-gxjx-hjqj"
    },
    {
      "type": "ADVISORY",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2024-23647"
    },
    {
      "type": "WEB",
      "url": "https://github.com/goauthentik/authentik/commit/38e04ae12720e5d81b4f7ac77997eb8d1275d31a"
    },
    {
      "type": "PACKAGE",
      "url": "https://github.com/goauthentik/authentik"
    }
  ],
  "schema_version": "1.4.0",
  "severity": [
    {
      "score": "CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:H/A:N",
      "type": "CVSS_V3"
    },
    {
      "score": "CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:P/VC:N/VI:H/VA:N/SC:N/SI:N/SA:N",
      "type": "CVSS_V4"
    }
  ],
  "summary": "Authentik vulnerable to PKCE downgrade attack"
}



Log in or create an account to share your comment.




Tags
Taxonomy of the tags.




Drag nodes to arrange them. Double-click a related vulnerability to open it, or a source to visit its link. The Physics button on the left tunes the layout and the simulation; the legend at the bottom left hides or shows nodes by kind and by sighting type.

Forecast uses a logistic model when the trend is rising, or an exponential decay model when the trend is falling. Fitted via linearized least squares.

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.
Vulnerability timeline

Sightings and recorded dates, grouped by day · UTC

JSON
How durations are calculated

Following the VTEM framework (Black Hat USA 2015), time to patch starts when the vendor or a coordinator was informed, total time to patch at discovery, and disclosure to patch at public disclosure; vendor response time runs from the report to its acknowledgement. Time to exploit and time unpatched start at the earliest discovery or report, falling back to public disclosure. Unpatched time ends at the first recorded patch, or the calculation time when no patch is recorded. Exploitation to patch shows the interval between those two events; a published proof of concept is a public exploit, not exploitation.

Each result shows its source dates. A negative interval means the end event came first; when date-only inputs leave the order open, the result says so. Date-only inputs are approximate. The earliest evidence wins: KEV report dates and sightings are labelled as such. Records describing another vulnerability are listed but never calculated from, and a PoC alone does not establish exploitation. Missing patch evidence does not prove that no patch exists. Filters below change the event list only.

Loading timeline…




    Related by attack behaviour

    Vulnerabilities whose description is nearest to this one in the vector space of the CIRCL/vulnerability-attack-technique-biencoder model. This is a similarity search over the bi-encoder space (plain cosine), not a classification, and it has no measured accuracy.