CVE-2025-62174

Executive Summary

CVE-2025-62174 is a security vulnerability in Mastodon, a free, open-source social network server based on ActivityPub. The flaw resides in the password reset functionality executed via the command-line interface using bin/tootctl accounts modify --reset-password. When an administrator resets a user's password through this method, the system fails to revoke the user's active sessions and access tokens. This oversight allows an attacker who has previously compromised a session or token to maintain persistent access to the account even after the password has been changed. The vulnerability has been assigned a CVSS score of 3.5 (Low), reflecting the requirement for prior compromise and administrative privileges for the reset action. Patches are available in Mastodon versions 4.2.27, 4.3.14, and 4.4.6.

Supply Chain & Package Security

Mastodon is distributed as a Ruby on Rails application via GitHub and Docker images. The vulnerability is not in a package dependency but in the core application logic. Administrators should ensure they are using patched versions from the official Mastodon repository. No malicious packages have been identified in the supply chain related to this CVE.

CVSS Breakdown & Threat Level

• CVSS Score: 3.5 (Low)
• Vector: CVSS:3.1/AV:N/AC:L/PR:H/UI:N/S:U/C:L/I:L/A:N
• Attack Vector (AV): Network (N) – The vulnerability can be exploited remotely.
• Attack Complexity (AC): Low (L) – No special conditions are required for exploitation.
• Privileges Required (PR): High (H) – An attacker must already have a valid session or token.
• User Interaction (UI): None (N) – No user action is needed for exploitation.
• Scope (S): Unchanged (U) – The vulnerability does not affect other components.
• Confidentiality (C): Low (L) – Limited information disclosure possible.
• Integrity (I): Low (L) – Limited ability to modify data.
• Availability (A): None (N) – No impact on system availability.

Threat Level: Low. Exploitation requires prior compromise of a session or token, and the impact is limited to continued access to a single account.

Deep Dive & Mechanics

The vulnerability is rooted in the password reset function within Mastodon's CLI tool (tootctl). When an administrator runs bin/tootctl accounts modify --reset-password, the system updates the password hash in the database but does not invalidate the user's existing sessions or OAuth access tokens. This is a classic case of Insufficient Session Expiration (CWE-613).

Attack Scenario:

1. An attacker compromises a user's session cookie or OAuth token (e.g., via XSS, phishing, or a previous data breach).
2. The legitimate user or an administrator detects the compromise and resets the password using the CLI tool.
3. The password is changed, but the attacker's session/token remains valid.
4. The attacker continues to access the account, potentially posting content, reading private messages, or performing other actions.

Why it happens: The tootctl command likely calls a method that updates the password but does not trigger the session/token revocation logic that is present in the web-based password reset flow. This is a missing step in the CLI implementation.

Vulnerable vs. Patched Code

Vulnerable Code (Conceptual):

# In lib/cli/accounts.rb or similar
def modify_account
  account = Account.find_by(username: options[:username])
  if options[:reset_password]
    account.password = new_password
    account.save!
    puts "Password reset successfully."
  end
end

Patched Code (Conceptual):

# In lib/cli/accounts.rb or similar
def modify_account
  account = Account.find_by(username: options[:username])
  if options[:reset_password]
    account.password = new_password
    account.save!
    # Revoke all sessions and tokens
    User.where(account_id: account.id).update_all(session_token: nil)
    Doorkeeper::AccessToken.where(resource_owner_id: account.user.id).update_all(revoked_at: Time.now.utc)
    puts "Password reset successfully. All sessions and tokens revoked."
  end
end

The patched version explicitly revokes all sessions and OAuth tokens associated with the user after a password reset.

Exploitation & Lab Setup

Red Team

Prerequisites:

• A valid session cookie or OAuth token for a target Mastodon account.
• Knowledge that the password will be reset (e.g., via social engineering or insider knowledge).

Exploitation Steps:

1. Obtain a valid session cookie (e.g., _session_id) or OAuth token for the target account.
2. Wait for the password reset to occur.
3. Use the captured session/token to make API requests:

   # Using a session cookie
   curl -X GET "https://mastodon.example/api/v1/accounts/verify_credentials" \
     -H "Cookie: _session_id=YOUR_SESSION_COOKIE"
   
   # Using an OAuth token
   curl -X GET "https://mastodon.example/api/v1/accounts/verify_credentials" \
     -H "Authorization: Bearer YOUR_ACCESS_TOKEN"
   

4. If the response is successful (HTTP 200), the session/token is still valid.
5. Continue to perform actions such as posting statuses, reading DMs, or changing profile settings.

Lab Setup:

• Deploy a vulnerable Mastodon instance (version < 4.2.27, < 4.3.14, or < 4.4.6) using Docker.
• Create a user account and obtain a session cookie.
• As an admin, reset the password via CLI.
• Attempt to use the old session cookie to verify persistence.

Blue Team

Detection:

• Monitor for API requests using session tokens that were created before a password reset event.
• Alert on any account activity following a password reset that does not originate from a new login.

Hunting:

• Query logs for tootctl accounts modify --reset-password commands.
• Correlate password reset events with subsequent API calls using old session IDs.

Response:

• If a compromised session is detected after a password reset, immediately revoke all sessions and tokens for that user.
• Force the user to re-authenticate and change their password again.

Indicators of Compromise (IOCs)

• Session Cookie: _session_id that remains valid after a password reset.
• OAuth Token: An access token that is not revoked after a password reset.
• Log Entries: Evidence of tootctl accounts modify --reset-password execution followed by continued API activity from the same session.
• Network Traffic: API calls to endpoints like /api/v1/accounts/verify_credentials or /api/v1/statuses using old credentials.

Detection Engineering

YARA Rule

rule Mastodon_Session_Not_Revoked {
  meta:
    description = "Detects Mastodon password reset without session revocation"
    author = "Valters IT"
    date = "2025-04-10"
    reference = "CVE-2025-62174"
  strings:
    $cli_reset = "tootctl accounts modify --reset-password"
    $session_update = "update_all(session_token: nil)"
    $token_revoke = "update_all(revoked_at: Time.now.utc)"
  condition:
    $cli_reset and not ($session_update or $token_revoke)
}

Sigma Rule

title: Mastodon Password Reset Without Session Revocation
id: 8a4b3c2d-1e5f-4a7b-9c8d-0e1f2a3b4c5d
status: experimental
description: Detects when a Mastodon admin resets a password via CLI without revoking sessions
author: Valters IT
date: 2025-04-10
logsource:
  product: linux
  service: auditd
detection:
  selection:
    type: 'EXECVE'
    a0|contains: 'tootctl'
    a1|contains: 'accounts'
    a2|contains: 'modify'
    a3|contains: '--reset-password'
  condition: selection
falsepositives:
  - Legitimate password resets that also revoke sessions (patched versions)
level: medium

Suricata Rule

alert http $HOME_NET any -> $EXTERNAL_NET any (
  msg:"Mastodon Post-Reset Session Reuse Detected";
  flow:to_server,established;
  content:"Cookie|3a| _session_id="; http_cookie;
  content:"/api/v1/"; http_uri;
  pcre:"/^\/api\/v1\/(accounts|statuses|timelines)/";
  sid:10000001;
  rev:1;
  reference:cve,2025-62174;
  classtype:attempted-user;
)

Remediation & Mitigation

Immediate Actions:

1. Upgrade Mastodon to version 4.2.27, 4.3.14, or 4.4.6 (or later).
2. If immediate upgrade is not possible, manually revoke all sessions and tokens after any CLI password reset:

   # In Rails console
   user = User.find_by(email: "user@example.com")
   user.update(session_token: nil)
   Doorkeeper::AccessToken.where(resource_owner_id: user.id).update_all(revoked_at: Time.now.utc)
   

Long-term Mitigations:

• Implement a mandatory session revocation step in the CLI password reset function.
• Add logging and alerting for password reset events.
• Educate administrators to use the web interface for password resets, which properly revokes sessions.

Workarounds:

• None officially provided. The only workaround is to manually revoke sessions after each CLI password reset.

Valters IT
Securing Digital Frontiers