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Fencer Vulns
medium 5.3

CVE-2026-33425 json

Discourse has inferable private group membership or existence via exclude_groups parameter

published 2026-03-20 7 mo ago modified 2026-09-08 2 mo ago also BIT-discourse-2026-33425 , EUVD-2026-13906 , GHSA-r6rh-xvf5-r5f2

cvss
5.3
version 3.1, NVD
cisa kev
Not listed
not in CISA's catalog
epss
0.7%
EPSS 0.7% chance of exploitation in 30 days, percentile 53%
public exploits
0
none known, plus a Nuclei check

Summary

Discourse is an open-source discussion platform. Prior to versions 2026.3.0-latest.1, 2026.2.1, and 2026.1.2, unauthenticated users can determine whether a specific user is a member of a private group by observing changes in directory results when using the `exclude_groups` parameter. Versions 2026.3.0-latest.1, 2026.2.1, and 2026.1.2 contain a patch. As a workaround, disable public access to the user directory via Admin → Settings → hide user profiles from public.

Patch / fix

  • bitnami discourse 2026.1.2, 2026.2.1, 2026.3.0
  • discourse discourse 2026.1.2, 2026.2.1

CISA SSVC

Exploitation
none
Automatable
no
Technical impact
partial
Assessed
7 mo ago

Exploit prediction

0.69% chance of exploitation in the next 30 days, higher than 53% of all scored CVEs (FIRST EPSS, 2026-11-08).

Exploits and checks

  • Nuclei template Discourse - Private Group Membership Inference via exclude_groups nuclei detection template

CVSS scores

assigned by version score vector
CNA 4.0 6.9 CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:L/VI:N/VA:N/SC:N/SI:N/SA:N
CNA 4.0 6.9 CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:L/VI:N/VA:N/SC:N/SI:N/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X
NVD 3.1 5.3 CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:N/A:N

Affected packages

ecosystem package affected fixed in
bitnami discourse
>=2026.1.0, <2026.1.2
>=2026.2.0, <2026.2.1
>=2026.3.0, <2026.3.0
2026.1.2
2026.2.1
2026.3.0

Affected products

  • discourse discourse

Classification

Weakness
  • CWE-203 Observable Discrepancy
  • CWE-639 Authorization Bypass Through User-Controlled Key
  • CWE-862 Missing Authorization

References

Sources

Fencer Vulns 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.

CPEs and fixed versions use Anchore's correction of NVD's data: Added CPE configurations because not yet analyzed by NVD.