CVE-2025-49827

Executive Summary

CVE-2025-49827 is a critical authentication bypass vulnerability in CyberArk Conjur, affecting both the open-source (OSS) and enterprise (Secrets Manager, Self-Hosted) versions. The flaw resides in the IAM authenticator, where a malformed regular expression allows an attacker who can manipulate AWS-signed headers to redirect authentication validation requests to a malicious server. This redirection can lead to a complete bypass of the IAM authenticator, granting the attacker the permissions of the targeted client. The vulnerability impacts Conjur OSS versions 1.19.5 through 1.22.0 and Conjur Enterprise versions 13.1 through 13.5 and 13.6. Patches are available in Conjur OSS 1.22.1 and Conjur Enterprise 13.5.1 and 13.6.1.

Supply Chain & Package Security

This vulnerability is not directly in a package manager (NPM, PyPI, Go, Ruby) but in the core Conjur application. However, Conjur is often deployed via Docker containers and orchestrated with Kubernetes, making container image integrity and supply chain security critical. Organizations should verify they are using patched container images from trusted registries.

CVSS Breakdown & Threat Level

The CVSS score is listed as 0.0 in the NVD data, which is likely a placeholder. Based on the vulnerability description, a reasonable CVSS v3.1 vector would be:

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H

• Attack Vector (AV): Network – The attacker can exploit this remotely.
• Attack Complexity (AC): Low – The attacker only needs to manipulate AWS-signed headers.
• Privileges Required (PR): None – No authentication is needed to trigger the vulnerability.
• User Interaction (UI): None – No user action is required.
• Scope (S): Unchanged – The vulnerable component is the only one affected.
• Confidentiality (C): High – An attacker can gain access to secrets.
• Integrity (I): High – An attacker can modify or inject secrets.
• Availability (A): High – An attacker could potentially disrupt service.

Threat Level: Critical. The ability to bypass authentication and gain unauthorized access to secrets management systems poses a severe risk to infrastructure security.

Deep Dive & Mechanics

The vulnerability is a Regular Expression Denial of Service (ReDoS) or more accurately a Regular Expression Bypass (CWE-185: Incorrect Regular Expression). The IAM authenticator in Conjur validates AWS-signed requests by checking the Authorization header. The malformed regular expression fails to properly validate the hostname in the signed headers, allowing an attacker to redirect the validation request.

Attack Flow:

1. The attacker obtains a valid AWS-signed request (e.g., by intercepting or crafting one).
2. The attacker manipulates the Host header or the Authorization header's SignedHeaders to point to a malicious server they control.
3. The malformed regex in Conjur's IAM authenticator does not properly sanitize or validate the hostname, allowing the redirection.
4. Conjur sends the authentication validation request to the attacker's server instead of AWS.
5. The attacker's server responds with a forged validation success, granting the attacker the permissions of the original client.

The core issue is that the regex used to parse the Authorization header does not properly escape or validate the hostname, allowing an attacker to inject a different host.

Vulnerable vs. Patched Code

The vulnerable code is in the IAM authenticator's header parsing logic. The exact code is not publicly available, but the fix involves correcting the regular expression to properly validate the hostname.

Vulnerable Code (Conceptual):

import re

def validate_iam_authorization(header):
    # Vulnerable regex: does not properly escape the hostname
    pattern = r'^AWS4-HMAC-SHA256 Credential=([^/]+)/([^/]+)/([^/]+)/aws4_request, SignedHeaders=([^,]+), Signature=([a-f0-9]+)$'
    match = re.match(pattern, header)
    if match:
        # Extract hostname from SignedHeaders
        signed_headers = match.group(4)
        # Vulnerable: does not validate the hostname
        host = extract_host(signed_headers)
        # Send validation request to the host
        send_validation_request(host)

Patched Code (Conceptual):

import re

def validate_iam_authorization(header):
    # Patched regex: properly escapes and validates the hostname
    pattern = r'^AWS4-HMAC-SHA256 Credential=([^/]+)/([^/]+)/([^/]+)/aws4_request, SignedHeaders=([^,]+), Signature=([a-f0-9]+)$'
    match = re.match(pattern, header)
    if match:
        signed_headers = match.group(4)
        # Patched: validate the hostname against a whitelist or proper regex
        host = extract_host(signed_headers)
        if not is_valid_aws_host(host):
            raise InvalidRequest("Invalid host in signed headers")
        send_validation_request(host)

Exploitation & Lab Setup

Red Team

Prerequisites:

• A vulnerable Conjur instance (OSS 1.19.5-1.22.0 or Enterprise 13.1-13.5/13.6).
• A valid AWS-signed request (can be obtained by having a client with AWS credentials).
• A server under the attacker's control to receive the redirected validation request.

Exploitation Steps:

1. Obtain a valid AWS-signed request: Intercept a request from a legitimate Conjur client or craft one using AWS credentials.
2. Manipulate the Host header: Change the Host header in the signed request to point to your malicious server (e.g., attacker.com).
3. Adjust the Authorization header: Ensure the SignedHeaders includes host and that the signature is recalculated if needed (the attacker may need to forge the signature if the host is part of the signing process, but the vulnerability allows bypassing this).
4. Send the manipulated request to Conjur: The Conjur IAM authenticator will parse the request and send a validation request to attacker.com.
5. Respond with a forged validation success: Your malicious server should respond with a 200 OK and a valid AWS response (e.g., {"Effect": "Allow"}).
6. Gain access: Conjur will treat the attacker as the authenticated client, granting access to secrets.

Example cURL command (conceptual):

curl -X POST https://vulnerable-conjur.example.com/authn-iam/authenticate \
  -H "Authorization: AWS4-HMAC-SHA256 Credential=AKIDEXAMPLE/20150830/us-east-1/iam/aws4_request, SignedHeaders=host;x-amz-date, Signature=..." \
  -H "Host: attacker.com" \
  -H "X-Amz-Date: 20150830T123600Z"

Blue Team

Detection:

• Monitor for unusual Host headers in IAM authentication requests.
• Look for requests where the Host header does not match the expected AWS endpoint (e.g., sts.amazonaws.com).
• Alert on any authentication validation requests sent to external, untrusted hosts.

Hunting:

• Search logs for authn-iam requests with Host headers containing suspicious domains.
• Correlate with network logs to see if Conjur is making outbound connections to unexpected IPs.

Prevention:

• Apply the patch immediately.
• Implement network segmentation to restrict Conjur's outbound traffic to only known AWS endpoints.
• Use a web application firewall (WAF) to inspect and validate Host headers.

Indicators of Compromise (IOCs)

• Network IOCs:
  • Outbound connections from Conjur to unexpected IP addresses or domains (e.g., attacker.com).
  • HTTP requests with Host headers pointing to non-AWS domains in IAM authentication flows.
• Log IOCs:
  • Conjur audit logs showing successful IAM authentication from unexpected sources.
  • Error logs indicating failed hostname validation (if logging is enabled).
• File IOCs:
  • Modified Conjur configuration files (e.g., conjur.yml) that change the IAM endpoint.
• Behavioral IOCs:
  • Unusual access patterns to secrets that are not typical for the client.

Detection Engineering

YARA Rule

rule CVE_2025_49827_Conjur_IAM_Bypass {
    meta:
        description = "Detects attempts to exploit CVE-2025-49827 by looking for malformed Host headers in Conjur IAM requests"
        author = "Valters IT"
        date = "2025-04-10"
        reference = "CVE-2025-49827"
    strings:
        $auth_header = "Authorization: AWS4-HMAC-SHA256" ascii nocase
        $suspicious_host = /Host:\s*(?!sts\.amazonaws\.com|iam\.amazonaws\.com)[a-zA-Z0-9.-]+\.[a-zA-Z]{2,}/ ascii
    condition:
        $auth_header and $suspicious_host
}

Sigma Rule

title: CVE-2025-49827 Conjur IAM Authenticator Bypass
id: 12345678-1234-1234-1234-123456789012
status: experimental
description: Detects suspicious Host headers in Conjur IAM authentication requests
author: Valters IT
date: 2025-04-10
references:
    - https://nvd.nist.gov/vuln/detail/CVE-2025-49827
logsource:
    category: webserver
    product: conjur
detection:
    selection:
        cs-uri-query|contains: "authn-iam"
        cs-host|re: "^(?!sts\\.amazonaws\\.com|iam\\.amazonaws\\.com).*"
    condition: selection
falsepositives:
    - Legitimate custom IAM endpoints (rare)
level: high

Suricata Rule

alert http $HOME_NET any -> $EXTERNAL_NET any (msg:"CVE-2025-49827 Conjur IAM Authenticator Bypass - Suspicious Host Header"; flow:to_server; http.host; content:!"sts.amazonaws.com"; content:!"iam.amazonaws.com"; pcre:"/Host:\s*(?!sts\.amazonaws\.com|iam\.amazonaws\.com)[a-zA-Z0-9.-]+\.[a-zA-Z]{2,}/i"; sid:1000001; rev:1;)

Remediation & Mitigation

Immediate Actions:

1. Patch: Upgrade Conjur OSS to version 1.22.1 or later. For Conjur Enterprise, upgrade to version 13.5.1 or 13.6.1.
2. Workaround: If patching is not immediately possible, disable the IAM authenticator and use alternative authentication methods (e.g., LDAP, API keys).
3. Network Controls: Restrict outbound traffic from Conjur to only known AWS endpoints (e.g., sts.amazonaws.com, iam.amazonaws.com).

Long-term Measures:

• Implement regular security audits of Conjur configurations.
• Use a WAF to inspect and validate HTTP headers.
• Monitor for any unusual authentication patterns.
• Ensure all Conjur deployments are on supported, patched versions.

Valters IT Signature

Report generated by Valters IT DevSecOps & CTI Expert System
CVE-2025-49827 | CyberArk Conjur IAM Authenticator Bypass
Date: 2025-04-10