CVE-2026-58555

Executive Summary

CVE-2026-58555 is a permission bypass vulnerability in the card module component. The vulnerability allows an attacker with local access to bypass permission checks, potentially leading to a denial of service (availability impact). The CVSS score is 6.6 (Medium), with a vector focusing on local access, low complexity, and high availability impact. No public proof-of-concept (PoC) or patch is currently available. The EPSS score is 0.0%, indicating low exploitation likelihood in the wild.

Supply Chain & Package Security

This vulnerability is not associated with any known package manager (NPM, PyPI, Go, Ruby). The card module appears to be a custom or proprietary component, not a widely distributed open-source package. No supply chain implications are identified at this time.

CVSS Breakdown & Threat Level

• CVSS Score: 6.6 (Medium)
• Vector: CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H
• Attack Vector (AV): Local – attacker must have local access to the system.
• Attack Complexity (AC): Low – no special conditions required.
• Privileges Required (PR): Low – attacker needs basic user privileges.
• User Interaction (UI): None – no user action required.
• Scope (S): Unchanged – vulnerability does not affect other components.
• Confidentiality (C): None – no data exposure.
• Integrity (I): None – no data modification.
• Availability (A): High – successful exploitation can cause denial of service.

Threat Level: Medium. The vulnerability requires local access, limiting remote exploitation. However, if an attacker gains local access, they can cause significant availability impact.

Deep Dive & Mechanics

The vulnerability resides in the card module, which likely handles permission checks for card-related operations (e.g., adding, removing, or modifying cards). The permission bypass occurs due to improper validation of user permissions, allowing an attacker to perform actions that should be restricted.

Root Cause: The module fails to properly verify the user's permissions before executing sensitive operations. This could be due to:

• Missing or incomplete permission checks in the code.
• Incorrect use of permission APIs.
• Race conditions in permission validation.

Attack Scenario:

1. An attacker gains local access to the system (e.g., via compromised user account).
2. The attacker sends crafted requests to the card module API, bypassing permission checks.
3. The module executes the requested operation (e.g., deleting a card), leading to denial of service.

Impact: Successful exploitation can disrupt card-related functionality, affecting availability of the service.

Vulnerable vs. Patched Code

Since no patch is available, the following is a hypothetical example of the vulnerable code pattern and a potential fix.

Vulnerable Code (Python-like pseudocode):

def delete_card(card_id, user):
    # Missing permission check
    card = Card.get(card_id)
    card.delete()
    return "Card deleted"

Patched Code (Hypothetical):

def delete_card(card_id, user):
    if not user.has_permission("delete_card"):
        raise PermissionError("Insufficient permissions")
    card = Card.get(card_id)
    card.delete()
    return "Card deleted"

The fix adds a permission check before executing the sensitive operation.

Exploitation & Lab Setup

Red Team

Objective: Exploit the permission bypass to cause denial of service.

Prerequisites:

• Local access to the system (e.g., SSH, RDP, or local terminal).
• A user account with low privileges.

Steps:

1. Identify the card module API endpoint (e.g., /api/card/delete).
2. Craft a request to delete a card without proper permissions.
3. Execute the request using a tool like curl or a custom script.

Example Command:

curl -X POST http://localhost/api/card/delete -d "card_id=123" -H "Authorization: Bearer <low_priv_token>"

Expected Outcome: The card is deleted, causing denial of service for card-related functionality.

Blue Team

Objective: Detect and prevent exploitation.

Detection:

• Monitor for unauthorized card deletion attempts.
• Log all permission failures and suspicious API calls.

Prevention:

• Implement strict permission checks in the card module.
• Use role-based access control (RBAC) to enforce least privilege.
• Apply the patch as soon as it becomes available.

Hunting:

• Search for logs showing permission bypass attempts.
• Look for unusual patterns in card deletion requests.

Indicators of Compromise (IOCs)

• Log Entries: Permission denied errors followed by successful card deletion.
• API Calls: Repeated requests to /api/card/delete from low-privileged users.
• System State: Missing or deleted cards without corresponding authorized actions.

Detection Engineering

YARA Rule

rule CVE_2026_58555_Card_Module_Permission_Bypass {
    meta:
        description = "Detects permission bypass in card module"
        author = "Valters IT"
        date = "2026-01-01"
        cve = "CVE-2026-58555"
    strings:
        $s1 = "delete_card" nocase
        $s2 = "permission" nocase
        $s3 = "bypass" nocase
    condition:
        all of them
}

Sigma Rule

title: Card Module Permission Bypass Attempt
id: 12345678-1234-1234-1234-123456789abc
status: experimental
description: Detects attempts to bypass permission checks in the card module
author: Valters IT
date: 2026/01/01
logsource:
    category: application
    product: card_module
detection:
    selection:
        EventID: 4625
        TargetObject: '*card*'
        AccessMask: '0x2'
    condition: selection
falsepositives:
    - Legitimate administrative actions
level: high

Suricata Rule

alert http any any -> any any (msg:"CVE-2026-58555 Card Module Permission Bypass"; flow:to_server; content:"/api/card/delete"; http_uri; classtype:attempted-admin; sid:1000001; rev:1;)

Remediation & Mitigation

Immediate Actions:

1. Restrict local access to the system to trusted users only.
2. Monitor logs for suspicious card deletion attempts.
3. Implement additional permission checks in the card module code.

Long-term Fix:

• Apply the official patch when released by the vendor.
• Conduct a security audit of the card module to identify other potential vulnerabilities.
• Implement least privilege principles across the application.

Workarounds:

• Disable the card module if not essential.
• Use network segmentation to limit local access.

Valters IT