Vulnerability-Lookup

GHSA-C9FV-CGMM-2WG7

Vulnerability from github – Published: 2026-08-18 17:59 – Updated: 2026-08-18 17:59

Summary

LibreNMS Vulnerable to Remote Code Execution by Signal Alert Transportation module

Details

Summary

A vulnerability has been identified that allows an authenticated administrator to execute arbitrary code on the host server. By adding an alert transport entry, an attacker with administrative privileges can execute malicious commands.

Details

The vulnerability is caused by an unsafe exec call in deliverAlert function of LibreNMS/Alert/Transport/Signal.php. Escapes for the path of signal-cli and the Recipient field are insufficient to prevent command-line injection.

The composer_wrapper.php under scripts is also vulnerable to command injection (unsafe exec calls) by passing the injected command as an argument, and it is accepting arguments passed by deliverAlert.

By chaining these unsafe exec calls, malicious admin user can execute any executables in the server's filesystem.

PoC

Under Dashboard -> Alert -> Alert Transports

Create a new Alert Transport entry. a. Select Signal as Transport type. b. Put ../scripts/composer_wrapper.php into Path. c. Put the command to execute under Recipient with ; at the start and the end of string.

. Click Save Transport, and after the popup closed, click Test Transport button under Action of the created Alert Transport entry.

The command is executed.

Impact

This vulnerability allows a malicious actor to achieve Remote Code Execution (RCE), potentially leading to complete system compromise, data exfiltration, or lateral movement within the network.

Remediation Advice

Escape user inputs, and avoid passing them directly into exec function. (scripts/composer_wrapper.php) Avoid setting executable paths directly in web interface. Instead, use a config value, and only allow setting executable paths by command line interface. (LibreNMS/Alert/Transport/Signal.php)

Severity

8.6 (High)


                  
                    CVSS:4.0/AV:N/AC:L/AT:N/PR:H/UI:N/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N

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JSON

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{
  "affected": [
    {
      "package": {
        "ecosystem": "Packagist",
        "name": "librenms/librenms"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "21.6.0"
            },
            {
              "fixed": "26.5.0"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ]
    }
  ],
  "aliases": [
    "CVE-2026-55182"
  ],
  "database_specific": {
    "cwe_ids": [
      "CWE-77"
    ],
    "github_reviewed": true,
    "github_reviewed_at": "2026-08-18T17:59:56Z",
    "nvd_published_at": null,
    "severity": "HIGH"
  },
  "details": "### Summary\nA vulnerability has been identified that allows an authenticated administrator to execute arbitrary code on the host server. By adding an alert transport entry, an attacker with administrative privileges can execute malicious commands.\n\n### Details\nThe vulnerability is caused by an unsafe `exec` call in `deliverAlert` function of `LibreNMS/Alert/Transport/Signal.php`. Escapes for the path of `signal-cli` and the `Recipient` field are insufficient to prevent command-line injection. \n\nThe `composer_wrapper.php` under `scripts` is also vulnerable to command injection (unsafe `exec` calls) by passing the injected command as an argument, and it is accepting arguments passed by `deliverAlert`.\n\nBy chaining these unsafe `exec` calls, malicious admin user can execute any executables in the server\u0027s filesystem.\n\n### PoC\n\n1. Under Dashboard -\u003e Alert -\u003e Alert Transports\n\n\u003cimg width=\"282\" height=\"273\" alt=\"image\" src=\"https://github.com/user-attachments/assets/b72f55b0-b782-47d0-b4f7-75f498019345\" /\u003e\n\n2. Create a new Alert Transport entry.\n    a. Select `Signal` as `Transport type`.\n    b. Put `../scripts/composer_wrapper.php` into `Path`.\n    c. Put the command to execute under `Recipient` with `;` at the start and the end of string.\n\n\u003cimg width=\"767\" height=\"391\" alt=\"image\" src=\"https://github.com/user-attachments/assets/5e34bfa8-4bd5-40cb-9624-0d40e40ccdc5\" /\u003e\n\n3. . Click `Save Transport`, and after the popup closed, click `Test Transport` button under `Action` of the created Alert Transport entry.\n\n\u003cimg width=\"172\" height=\"90\" alt=\"image\" src=\"https://github.com/user-attachments/assets/7f83db07-fbf9-4be6-b247-533a6d7b9828\" /\u003e\n\n4. The command is executed.\n\u003cimg width=\"532\" height=\"216\" alt=\"image\" src=\"https://github.com/user-attachments/assets/d595b0fe-10cc-4050-b4b9-d290b658689d\" /\u003e\n\n### Impact\nThis vulnerability allows a malicious actor to achieve Remote Code Execution (RCE), potentially leading to complete system compromise, data exfiltration, or lateral movement within the network.\n\n### Remediation Advice\nEscape user inputs, and avoid passing them directly into `exec` function. (`scripts/composer_wrapper.php`)\nAvoid setting executable paths directly in web interface. Instead, use a config value, and only allow setting executable paths by command line interface. (`LibreNMS/Alert/Transport/Signal.php`)",
  "id": "GHSA-c9fv-cgmm-2wg7",
  "modified": "2026-08-18T17:59:56Z",
  "published": "2026-08-18T17:59:56Z",
  "references": [
    {
      "type": "WEB",
      "url": "https://github.com/librenms/librenms/security/advisories/GHSA-c9fv-cgmm-2wg7"
    },
    {
      "type": "PACKAGE",
      "url": "https://github.com/librenms/librenms"
    },
    {
      "type": "WEB",
      "url": "https://github.com/librenms/librenms/releases/tag/26.5.0"
    }
  ],
  "schema_version": "1.4.0",
  "severity": [
    {
      "score": "CVSS:4.0/AV:N/AC:L/AT:N/PR:H/UI:N/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N",
      "type": "CVSS_V4"
    }
  ],
  "summary": "LibreNMS Vulnerable to Remote Code Execution by Signal Alert Transportation module"
}

CVE-2026-55182 (GCVE-0-2026-55182)

Vulnerability from cvelistv5 – Published: 2026-08-26 21:50 – Updated: 2026-08-27 13:47

Title

LibreNMS: Remote Code Execution by Signal Alert Transportation Module

Summary

LibreNMS is a network monitoring system. In versions from 21.6.0 up to 26.5.0, the Signal alert transport is vulnerable to command injection because the signal-cli path and the Recipient field of an alert transport entry are insufficiently escaped before being passed to an exec call. An authenticated administrator can craft a transport entry whose Recipient contains shell metacharacters and whose path points to the bundled composer_wrapper.php script, which itself passes attacker-controlled input to further unsafe exec calls. By chaining these calls, the administrator can execute arbitrary operating-system commands on the LibreNMS host. This issue is fixed in version 26.5.0.

Severity

8.6 (High)


                        
                          CVSS:4.0/AV:N/AC:L/AT:N/PR:H/UI:N/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N

SSVC

Exploitation: poc Automatable: no Technical Impact: total

CISA Coordinator · CISA-ADP (v2.0.3)

Decision recorded 2026-08-27 13:47 UTC

CWE

CWE-77 - Improper Neutralization of Special Elements used in a Command ('Command Injection')

Assigner

GitHub_M mitre root

References

3 references

URL	Tags
https://github.com/librenms/librenms/security/adv…	x_refsource_CONFIRM
https://github.com/librenms/librenms/commit/868e3b966a	x_refsource_MISC
https://github.com/librenms/librenms/releases/tag…	x_refsource_MISC

Impacted products

1 product

Vendor	Product	Version
librenms	librenms	Affected: >= 21.6.0, < 26.5.0

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JSON

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{
  "containers": {
    "adp": [
      {
        "metrics": [
          {
            "other": {
              "content": {
                "id": "CVE-2026-55182",
                "options": [
                  {
                    "Exploitation": "poc"
                  },
                  {
                    "Automatable": "no"
                  },
                  {
                    "Technical Impact": "total"
                  }
                ],
                "role": "CISA Coordinator",
                "timestamp": "2026-08-27T13:47:03.373245Z",
                "version": "2.0.3"
              },
              "type": "ssvc"
            }
          }
        ],
        "providerMetadata": {
          "dateUpdated": "2026-08-27T13:47:10.632Z",
          "orgId": "134c704f-9b21-4f2e-91b3-4a467353bcc0",
          "shortName": "CISA-ADP"
        },
        "references": [
          {
            "tags": [
              "exploit"
            ],
            "url": "https://github.com/librenms/librenms/security/advisories/GHSA-c9fv-cgmm-2wg7"
          }
        ],
        "title": "CISA ADP Vulnrichment"
      }
    ],
    "cna": {
      "affected": [
        {
          "product": "librenms",
          "vendor": "librenms",
          "versions": [
            {
              "status": "affected",
              "version": "\u003e= 21.6.0, \u003c 26.5.0"
            }
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        }
      ],
      "descriptions": [
        {
          "lang": "en",
          "value": "LibreNMS is a network monitoring system. In versions from 21.6.0 up to 26.5.0, the Signal alert transport is vulnerable to command injection because the signal-cli path and the Recipient field of an alert transport entry are insufficiently escaped before being passed to an exec call. An authenticated administrator can craft a transport entry whose Recipient contains shell metacharacters and whose path points to the bundled composer_wrapper.php script, which itself passes attacker-controlled input to further unsafe exec calls. By chaining these calls, the administrator can execute arbitrary operating-system commands on the LibreNMS host. This issue is fixed in version 26.5.0."
        }
      ],
      "metrics": [
        {
          "cvssV4_0": {
            "attackComplexity": "LOW",
            "attackRequirements": "NONE",
            "attackVector": "NETWORK",
            "baseScore": 8.6,
            "baseSeverity": "HIGH",
            "privilegesRequired": "HIGH",
            "subAvailabilityImpact": "NONE",
            "subConfidentialityImpact": "NONE",
            "subIntegrityImpact": "NONE",
            "userInteraction": "NONE",
            "vectorString": "CVSS:4.0/AV:N/AC:L/AT:N/PR:H/UI:N/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N",
            "version": "4.0",
            "vulnAvailabilityImpact": "HIGH",
            "vulnConfidentialityImpact": "HIGH",
            "vulnIntegrityImpact": "HIGH"
          }
        }
      ],
      "problemTypes": [
        {
          "descriptions": [
            {
              "cweId": "CWE-77",
              "description": "CWE-77: Improper Neutralization of Special Elements used in a Command (\u0027Command Injection\u0027)",
              "lang": "en",
              "type": "CWE"
            }
          ]
        }
      ],
      "providerMetadata": {
        "dateUpdated": "2026-08-26T21:50:04.014Z",
        "orgId": "a0819718-46f1-4df5-94e2-005712e83aaa",
        "shortName": "GitHub_M"
      },
      "references": [
        {
          "name": "https://github.com/librenms/librenms/security/advisories/GHSA-c9fv-cgmm-2wg7",
          "tags": [
            "x_refsource_CONFIRM"
          ],
          "url": "https://github.com/librenms/librenms/security/advisories/GHSA-c9fv-cgmm-2wg7"
        },
        {
          "name": "https://github.com/librenms/librenms/commit/868e3b966a",
          "tags": [
            "x_refsource_MISC"
          ],
          "url": "https://github.com/librenms/librenms/commit/868e3b966a"
        },
        {
          "name": "https://github.com/librenms/librenms/releases/tag/26.5.0",
          "tags": [
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      "source": {
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      "title": "LibreNMS: Remote Code Execution by Signal Alert Transportation Module"
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  "cveMetadata": {
    "assignerOrgId": "a0819718-46f1-4df5-94e2-005712e83aaa",
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    "datePublished": "2026-08-26T21:50:04.014Z",
    "dateReserved": "2026-06-16T15:20:43.086Z",
    "dateUpdated": "2026-08-27T13:47:10.632Z",
    "state": "PUBLISHED"
  },
  "dataType": "CVE_RECORD",
  "dataVersion": "5.2"
}

Sightings

Author	Source	Type	Date	Other

Nomenclature

Seen: The vulnerability was mentioned, discussed, or observed by the user.
Confirmed: The vulnerability has been validated from an analyst's perspective.
Published Proof of Concept: A public proof of concept is available for this vulnerability.
Exploited: The vulnerability was observed as exploited by the user who reported the sighting.
Patched: The vulnerability was observed as successfully patched by the user who reported the sighting.
Not exploited: The vulnerability was not observed as exploited by the user who reported the sighting.
Not confirmed: The user expressed doubt about the validity of the vulnerability.
Not patched: The vulnerability was not observed as successfully patched by the user who reported the sighting.

Detection rules are retrieved from Rulezet.

The MITRE ATT&CK techniques below are AI-generated suggestions, inferred from the description of the vulnerability by the CIRCL/vulnerability-attack-technique-classification-roberta-base model, served locally by ML-Gateway. They have not been verified by an analyst and are provided for guidance only.
The approach is described in our paper Mapping CVEs to MITRE ATT&CK Techniques: A Curated Gold-Set Classifier and the Limits of LLM-Assisted Label Expansion.

Action not permitted

GHSA-C9FV-CGMM-2WG7

Summary

Details

PoC

Impact

Remediation Advice

CVE-2026-55182 (GCVE-0-2026-55182)

Tags

Sightings

Nomenclature