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Fencer Intel
medium 6.5

CVE-2024-23647 json

PKCE downgrade attack in Authentik

published 2y ago modified 2mo ago also BIT-authentik-2024-23647 , EUVD-2024-0389 , GHSA-mrx3-gxjx-hjqj , GO-2024-2479

cvss
6.5
version 3.1, CNA
cisa kev
Not listed
not in CISA's catalog
epss
0.5%
EPSS 0.5% chance of exploitation in 30 days, percentile 46%
public exploits
0
none known

Summary

Authentik is an open-source Identity Provider. 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 the code_verifier parameter to the token request. Prior to 2023.8.7 and 2023.10.7, a downgrade scenario is possible: if the attacker removes the code_challenge parameter from the authorization request, authentik will not do the PKCE check. Because of this bug, an attacker can circumvent the protection PKCE offers, such as CSRF attacks and code injection attacks. Versions 2023.8.7 and 2023.10.7 fix the issue.

Patch / fix

  • go goauthentik.io 2023.8.7, 2023.10.7
  • bitnami authentik 2023.8.7, 2023.10.7
  • goauthentik authentik 2023.8.7, 2023.10.7

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CISA SSVC

Exploitation
none
Automatable
no
Technical impact
total
Assessed
2y ago

Exploit prediction

0.55% chance of exploitation in the next 30 days, higher than 46% of all scored CVEs (FIRST EPSS, 2026-11-11).

CVSS scores

assigned by version score vector
CNA 3.1 6.5 CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:H/A:N
GitHub 3.1 6.5 CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:H/A:N
NVD 3.1 8.8 CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H
OSV 3.1 8.8 CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H

Affected packages

ecosystem package affected fixed in
go goauthentik.io
>=2023.10.0, <2023.10.7
<2023.8.7
all versions
2023.10.7
2023.8.7
bitnami authentik
<2023.8.7
>=2023.10.0, <2023.10.7
2023.8.7
2023.10.7

Affected products

  • goauthentik authentik

Classification

Weakness

References

Sources

Fencer Intel keeps one entry per vulnerability: the CVE id wins, then GHSA, and records that alias each other are merged, except that two CVEs always keep separate entries. The same data is available as JSON.