Log Parsing Flaw in luci-app-banip Enables IP Injection

Executive Summary

CVE-2026-62184 is a log parsing vulnerability in luci-app-banip, a tool used to block IP addresses based on log entries. The vulnerability arises from an awk-based parser that extracts the first IPv4 address from log lines without considering the field position. This flaw allows attackers to inject arbitrary IP addresses into fields like usernames, which are attacker-controlled.

An unauthenticated remote attacker can exploit this by entering a crafted IP address in the login username field. As a result, banIP may block the injected IP instead of the attacker's actual IP, leaving the attacker unblocked and able to continue malicious activities.

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Detection Guidance

Detecting this vulnerability involves checking for signs of IP injection in logs or banIP configurations. Since the vulnerability stems from an awk-based parser extracting the first IPv4 address from log lines without validating the field context, you can inspect logs for unusual or attacker-controlled fields (e.g., usernames containing IP-like strings).

• Review banIP logs for unexpected IP blocks or entries where the blocked IP does not match the expected source of the log event. For example, check for IPs appearing in username fields or other non-standard fields.
• Use grep or awk to search for log lines where the username field contains an IP address. Example command: `grep -E 'username=[0-9]{1,3}\.[0-9]{1,3}\.[0-9]{1,3}\.[0-9]{1,3}' /var/log/banip.log`.
• Inspect the banIP configuration or rules to see if any IPs have been added unexpectedly. Example command: `cat /etc/banip/banip.deny` or `iptables -L -n | grep DROP`.

If the system uses luci-app-banip, verify the version and check for updates or patches that address this vulnerability.

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Impact Analysis

This vulnerability can have several impacts:

• False blocking of legitimate IPs: Attackers can trick the system into blocking innocent users or systems by injecting their IPs into logs, disrupting their access.
• Evasion of security measures: The real attacker remains unblocked, allowing them to continue launching attacks or probing the system without being detected or mitigated.
• Operational disruption: Legitimate users or services may be incorrectly blocked, leading to downtime or degraded performance for critical systems.
• Reputation damage: If legitimate users or services are blocked, it could harm trust in the affected system or organization.

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Compliance Impact

This vulnerability may impact compliance with common standards and regulations in the following ways:

• GDPR (General Data Protection Regulation): If the vulnerability leads to the blocking of legitimate users or systems, it could disrupt access to personal data or services, potentially violating GDPR's requirements for data availability and integrity. Additionally, if the vulnerability is exploited to evade detection, it may hinder an organization's ability to protect personal data from unauthorized access.
• HIPAA (Health Insurance Portability and Accountability Act): For organizations handling protected health information (PHI), this vulnerability could lead to unauthorized access or disruption of services. If attackers exploit the flaw to remain unblocked, they may gain persistent access to systems containing PHI, violating HIPAA's security and integrity requirements.
• Other standards (e.g., ISO 27001, NIST): The vulnerability undermines security controls related to access management and log integrity. Failure to address such vulnerabilities could result in non-compliance with requirements for monitoring, incident response, and risk management.

Organizations should assess the risk posed by this vulnerability and implement mitigations to ensure continued compliance with applicable regulations.

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Mitigation Strategies

To mitigate this vulnerability, follow these immediate steps:

• Update luci-app-banip to the latest version if a patch is available. Check the project's repository or package manager for updates.
• Modify the awk-based log parser to validate the field context before extracting IP addresses. Ensure the parser only extracts IPs from the expected log fields (e.g., source IP field) and ignores attacker-controlled fields like usernames.
• Implement input validation for log fields to prevent IP injection. For example, sanitize or reject log entries where usernames or other attacker-controlled fields contain IP-like strings.
• Monitor banIP logs for suspicious activity, such as unexpected IP blocks or IPs appearing in unusual fields. Set up alerts for anomalous log entries.
• Temporarily disable banIP if the vulnerability cannot be patched immediately, and rely on alternative firewall rules or intrusion prevention systems until a fix is applied.

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