Vulnerability-Lookup

CVE-2026-55584 (GCVE-0-2026-55584)

Vulnerability from cvelistv5 – Published: 2026-08-28 18:29 – Updated: 2026-08-31 18:54

Title

phpSysInfo: IP allowlist (PSI_ALLOWED) bypass via spoofed X-Forwarded-For / Client-IP headers

Summary

phpSysInfo is a customizable PHP script that displays system information. Prior to 3.4.6, the PSI_ALLOWED access-control check in read_config.php trusts attacker-controlled X-Forwarded-For and Client-IP HTTP headers before REMOTE_ADDR. A remote unauthenticated attacker can supply an allowed address in one of these headers to impersonate a trusted client and access exposed hostname, kernel, CPU, memory, filesystem, and network-interface information. This issue is fixed in version 3.4.6.

Severity

7.5 (High)


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

SSVC

Exploitation: none Automatable: yes Technical Impact: partial

CISA Coordinator · CISA-ADP (v2.0.3)

Decision recorded 2026-08-31 15:42 UTC

CWE

CWE-290 - Authentication Bypass by Spoofing

Assigner

GitHub_M mitre root

References

3 references

URL	Tags
https://github.com/phpsysinfo/phpsysinfo/security…	x_refsource_CONFIRM
https://github.com/phpsysinfo/phpsysinfo/commit/0…	x_refsource_MISC
https://github.com/phpsysinfo/phpsysinfo/releases…	x_refsource_MISC

Impacted products

1 product

Vendor	Product	Version	CPE status
phpsysinfo	phpsysinfo	Affected: < 3.4.6	guessed

Show details on NVD website

JSON

To clipboard

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FKIE_CVE-2026-55584

Vulnerability from fkie_nvd - Published: 2026-08-28 20:18 - Updated: 2026-08-31 19:17

Severity

7.5 (High) - CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N

Summary

References

	URL	Tags
	security-advisories@github.com	https://github.com/phpsysinfo/phpsysinfo/commit/019fa2d7e568ea11461adb4bd33da5dc87c4b9ab
	security-advisories@github.com	https://github.com/phpsysinfo/phpsysinfo/releases/tag/v3.4.6
	security-advisories@github.com	https://github.com/phpsysinfo/phpsysinfo/security/advisories/GHSA-786w-p5pm-cvgh

Impacted products

	Vendor	Product	Version

JSON

To clipboard

{
  "affected": [
    {
      "affectedData": [
        {
          "product": "phpsysinfo",
          "vendor": "phpsysinfo",
          "versions": [
            {
              "status": "affected",
              "version": "\u003c 3.4.6"
            }
          ]
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    }
  ],
  "id": "CVE-2026-55584",
  "lastModified": "2026-08-31T19:17:00.940",
  "metrics": {
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        "type": "Secondary"
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  "references": [
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    },
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      "source": "security-advisories@github.com",
      "url": "https://github.com/phpsysinfo/phpsysinfo/releases/tag/v3.4.6"
    },
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    }
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}

GHSA-786W-P5PM-CVGH

Vulnerability from github – Published: 2026-08-28 18:30 – Updated: 2026-08-28 18:30

Summary

phpSysInfo has an IP allowlist (PSI_ALLOWED) bypass via spoofed X-Forwarded-For / Client-IP headers

Details

Summary

phpSysInfo's PSI_ALLOWED IP allowlist can be trivially bypassed by any unauthenticated remote attacker. The access-control check in read_config.php derives the client IP from the attacker-controlled X-Forwarded-For and Client-IP HTTP headers before falling back to REMOTE_ADDR. An attacker can send X-Forwarded-For: <an allowed IP> to impersonate a trusted address and gain full access to all exposed system information, defeating the only IP-based access restriction the application provides.

Affected component

File: read_config.php
Versions: all versions up to and including 3.4.x (current main)

Description

When PSI_ALLOWED is configured, read_config.php enforces an IP allowlist. The client IP is resolved as follows:

if (isset($_SERVER["HTTP_X_FORWARDED_FOR"])) {
    $ip = $_SERVER["HTTP_X_FORWARDED_FOR"];
} else {
    if (isset($_SERVER["HTTP_CLIENT_IP"])) {
        $ip = $_SERVER["HTTP_CLIENT_IP"];
    } else {
        $ip = $_SERVER["REMOTE_ADDR"];
    }
}

Both HTTP_X_FORWARDED_FOR and HTTP_CLIENT_IP are fully attacker-controlled request headers. They are trusted unconditionally and take priority over REMOTE_ADDR. There is no concept of a configured/trusted reverse proxy, so even when phpSysInfo is exposed directly (no proxy in front), the spoofed header wins. As a result the allowlist provides no real protection.

Proof of Concept

Verified against phpSysInfo 3.4.x-main-d786ab2 running in a local Docker container (php:8.2-apache).

Deployment with the allowlist (under [main]) restricted to an address the attacker does not own:

; phpsysinfo.ini  ([main] section)
ALLOWED=8.8.8.8

Request without the spoofed header — correctly denied (attacker's real IP is the container gateway 172.17.0.1):

$ curl -s http://localhost:8080/xml.php | head -c 200
Client IP address (172.17.0.1) not allowed.

Request with a spoofed X-Forwarded-For matching the allowlist — bypass, full system information returned:

$ curl -s -H "X-Forwarded-For: 8.8.8.8" http://localhost:8080/xml.php | head -c 200
<?xml version="1.0" encoding="UTF-8"?>
<tns:phpsysinfo xmlns:tns="http://phpsysinfo.sourceforge.net/" ...>

The same bypass works with the Client-IP header (HTTP_CLIENT_IP), which is also trusted before REMOTE_ADDR.

Impact

Any remote, unauthenticated attacker can defeat the PSI_ALLOWED access restriction and read the complete system information exposed by phpSysInfo, including hostname, kernel version, CPU model, memory layout, mounted filesystems, and all network interface addresses. This information is valuable for reconnaissance and targeting of further attacks.

Remediation

Use REMOTE_ADDR as the authoritative client IP by default. Only honor X-Forwarded-For / Client-IP when the request originates from an explicitly configured list of trusted proxies, and when honoring it, parse the correct entry from the chain rather than trusting the whole header. Example direction:

$ip = $_SERVER["REMOTE_ADDR"];
if (defined('PSI_TRUSTED_PROXIES') && in_array($ip, $trusted_proxies, true)
    && isset($_SERVER["HTTP_X_FORWARDED_FOR"])) {
    // take the right-most untrusted hop from the XFF chain
    $parts = array_map('trim', explode(',', $_SERVER["HTTP_X_FORWARDED_FOR"]));
    $ip = end($parts);
}

Discovery / Credit

Reported by: Muhammed Mirac Kayıkci
Coordinated disclosure; no third-party systems were tested. Verification performed against a local Docker deployment only.

Severity

7.5 (High)


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

Show details on source website

JSON

To clipboard

{
  "affected": [
    {
      "database_specific": {
        "last_known_affected_version_range": "\u003c= 3.4.5"
      },
      "package": {
        "ecosystem": "Packagist",
        "name": "phpsysinfo/phpsysinfo"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "0"
            },
            {
              "fixed": "3.4.6"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ]
    }
  ],
  "aliases": [
    "CVE-2026-55584"
  ],
  "database_specific": {
    "cwe_ids": [
      "CWE-290"
    ],
    "github_reviewed": true,
    "github_reviewed_at": "2026-08-28T18:30:55Z",
    "nvd_published_at": null,
    "severity": "HIGH"
  },
  "details": "## Summary\nphpSysInfo\u0027s `PSI_ALLOWED` IP allowlist can be trivially bypassed by any unauthenticated remote attacker. The access-control check in `read_config.php` derives the client IP from the attacker-controlled `X-Forwarded-For` and `Client-IP` HTTP headers **before** falling back to `REMOTE_ADDR`. An attacker can send `X-Forwarded-For: \u003can allowed IP\u003e` to impersonate a trusted address and gain full access to all exposed system information, defeating the only IP-based access restriction the application provides.\n\n## Affected component\n- File: `read_config.php`\n- Versions: all versions up to and including 3.4.x (current `main`)\n\n## Description\nWhen `PSI_ALLOWED` is configured, `read_config.php` enforces an IP allowlist. The client IP is resolved as follows:\n\n```php\nif (isset($_SERVER[\"HTTP_X_FORWARDED_FOR\"])) {\n    $ip = $_SERVER[\"HTTP_X_FORWARDED_FOR\"];\n} else {\n    if (isset($_SERVER[\"HTTP_CLIENT_IP\"])) {\n        $ip = $_SERVER[\"HTTP_CLIENT_IP\"];\n    } else {\n        $ip = $_SERVER[\"REMOTE_ADDR\"];\n    }\n}\n```\n\nBoth `HTTP_X_FORWARDED_FOR` and `HTTP_CLIENT_IP` are fully attacker-controlled request headers. They are trusted unconditionally and take priority over `REMOTE_ADDR`. There is no concept of a configured/trusted reverse proxy, so even when phpSysInfo is exposed directly (no proxy in front), the spoofed header wins. As a result the allowlist provides no real protection.\n\n## Proof of Concept\nVerified against phpSysInfo `3.4.x-main-d786ab2` running in a local Docker container (`php:8.2-apache`).\n\nDeployment with the allowlist (under `[main]`) restricted to an address the attacker does not own:\n\n```ini\n; phpsysinfo.ini  ([main] section)\nALLOWED=8.8.8.8\n```\n\nRequest without the spoofed header \u2014 correctly denied (attacker\u0027s real IP is the container gateway `172.17.0.1`):\n\n```bash\n$ curl -s http://localhost:8080/xml.php | head -c 200\nClient IP address (172.17.0.1) not allowed.\n```\n\nRequest with a spoofed `X-Forwarded-For` matching the allowlist \u2014 bypass, full system information returned:\n\n```bash\n$ curl -s -H \"X-Forwarded-For: 8.8.8.8\" http://localhost:8080/xml.php | head -c 200\n\u003c?xml version=\"1.0\" encoding=\"UTF-8\"?\u003e\n\u003ctns:phpsysinfo xmlns:tns=\"http://phpsysinfo.sourceforge.net/\" ...\u003e\n```\n\nThe same bypass works with the `Client-IP` header (`HTTP_CLIENT_IP`), which is also trusted before `REMOTE_ADDR`.\n\n## Impact\nAny remote, unauthenticated attacker can defeat the `PSI_ALLOWED` access restriction and read the complete system information exposed by phpSysInfo, including hostname, kernel version, CPU model, memory layout, mounted filesystems, and all network interface addresses. This information is valuable for reconnaissance and targeting of further attacks.\n\n## Remediation\nUse `REMOTE_ADDR` as the authoritative client IP by default. Only honor `X-Forwarded-For` / `Client-IP` when the request originates from an explicitly configured list of trusted proxies, and when honoring it, parse the correct entry from the chain rather than trusting the whole header. Example direction:\n\n```php\n$ip = $_SERVER[\"REMOTE_ADDR\"];\nif (defined(\u0027PSI_TRUSTED_PROXIES\u0027) \u0026\u0026 in_array($ip, $trusted_proxies, true)\n    \u0026\u0026 isset($_SERVER[\"HTTP_X_FORWARDED_FOR\"])) {\n    // take the right-most untrusted hop from the XFF chain\n    $parts = array_map(\u0027trim\u0027, explode(\u0027,\u0027, $_SERVER[\"HTTP_X_FORWARDED_FOR\"]));\n    $ip = end($parts);\n}\n```\n\n## Discovery / Credit\n- Reported by: Muhammed Mirac Kay\u0131kci\n- Coordinated disclosure; no third-party systems were tested. Verification performed against a local Docker deployment only.",
  "id": "GHSA-786w-p5pm-cvgh",
  "modified": "2026-08-28T18:30:55Z",
  "published": "2026-08-28T18:30:55Z",
  "references": [
    {
      "type": "WEB",
      "url": "https://github.com/phpsysinfo/phpsysinfo/security/advisories/GHSA-786w-p5pm-cvgh"
    },
    {
      "type": "WEB",
      "url": "https://github.com/phpsysinfo/phpsysinfo/commit/019fa2d7e568ea11461adb4bd33da5dc87c4b9ab"
    },
    {
      "type": "PACKAGE",
      "url": "https://github.com/phpsysinfo/phpsysinfo"
    },
    {
      "type": "WEB",
      "url": "https://github.com/phpsysinfo/phpsysinfo/releases/tag/v3.4.6"
    }
  ],
  "schema_version": "1.4.0",
  "severity": [
    {
      "score": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N",
      "type": "CVSS_V3"
    }
  ],
  "summary": "phpSysInfo has an IP allowlist (PSI_ALLOWED) bypass via spoofed X-Forwarded-For / Client-IP headers"
}

ubuntu-cve-2026-55584

Vulnerability from osv_ubuntu

Published

2026-08-31 00:00

Modified

2026-08-31 00:00

Summary

Details

Severity

7.5 (High)


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

N/A (UNKNOWN)


                    
                      medium

References

URL

Type

	https://ubuntu.com/security/CVE-2026-55584	REPORT
	https://www.cve.org/CVERecord?id=CVE-2026-55584	REPORT
	https://github.com/phpsysinfo/phpsysinfo/security…	REPORT
	https://github.com/phpsysinfo/phpsysinfo/commit/0…	REPORT
	https://github.com/phpsysinfo/phpsysinfo/commit/0…	REPORT
	https://github.com/phpsysinfo/phpsysinfo/releases…	REPORT

JSON

To clipboard

{
  "affected": [
    {
      "ecosystem_specific": {
        "binaries": [
          {
            "binary_name": "phpsysinfo",
            "binary_version": "3.2.1-1ubuntu3"
          }
        ]
      },
      "package": {
        "ecosystem": "Ubuntu:16.04:LTS",
        "name": "phpsysinfo",
        "purl": "pkg:deb/ubuntu/phpsysinfo@3.2.1-1ubuntu3?arch=source\u0026distro=xenial"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "0"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ],
      "versions": [
        "3.0.17-1ubuntu1",
        "3.2.1-1ubuntu1",
        "3.2.1-1ubuntu2",
        "3.2.1-1ubuntu3"
      ]
    },
    {
      "ecosystem_specific": {
        "binaries": [
          {
            "binary_name": "phpsysinfo",
            "binary_version": "3.2.5-3ubuntu1"
          }
        ]
      },
      "package": {
        "ecosystem": "Ubuntu:18.04:LTS",
        "name": "phpsysinfo",
        "purl": "pkg:deb/ubuntu/phpsysinfo@3.2.5-3ubuntu1?arch=source\u0026distro=bionic"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "0"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ],
      "versions": [
        "3.2.5-3ubuntu1"
      ]
    },
    {
      "ecosystem_specific": {
        "binaries": [
          {
            "binary_name": "phpsysinfo",
            "binary_version": "3.2.5-3ubuntu1"
          }
        ]
      },
      "package": {
        "ecosystem": "Ubuntu:20.04:LTS",
        "name": "phpsysinfo",
        "purl": "pkg:deb/ubuntu/phpsysinfo@3.2.5-3ubuntu1?arch=source\u0026distro=focal"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "0"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ],
      "versions": [
        "3.2.5-3ubuntu1"
      ]
    },
    {
      "ecosystem_specific": {
        "binaries": [
          {
            "binary_name": "phpsysinfo",
            "binary_version": "3.2.5-3ubuntu1"
          }
        ]
      },
      "package": {
        "ecosystem": "Ubuntu:22.04:LTS",
        "name": "phpsysinfo",
        "purl": "pkg:deb/ubuntu/phpsysinfo@3.2.5-3ubuntu1?arch=source\u0026distro=jammy"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "0"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ],
      "versions": [
        "3.2.5-3ubuntu1"
      ]
    },
    {
      "ecosystem_specific": {
        "binaries": [
          {
            "binary_name": "phpsysinfo",
            "binary_version": "3.4.3-3"
          }
        ]
      },
      "package": {
        "ecosystem": "Ubuntu:24.04:LTS",
        "name": "phpsysinfo",
        "purl": "pkg:deb/ubuntu/phpsysinfo@3.4.3-3?arch=source\u0026distro=noble"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "0"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ],
      "versions": [
        "3.4.3-1",
        "3.4.3-3"
      ]
    },
    {
      "ecosystem_specific": {
        "binaries": [
          {
            "binary_name": "phpsysinfo",
            "binary_version": "3.4.4-1"
          }
        ]
      },
      "package": {
        "ecosystem": "Ubuntu:26.04:LTS",
        "name": "phpsysinfo",
        "purl": "pkg:deb/ubuntu/phpsysinfo@3.4.4-1?arch=source\u0026distro=resolute"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "0"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ],
      "versions": [
        "3.4.4-1"
      ]
    }
  ],
  "aliases": [],
  "details": "phpSysInfo is a customizable PHP script that displays system information. Prior to 3.4.6, the PSI_ALLOWED access-control check in read_config.php trusts attacker-controlled X-Forwarded-For and Client-IP HTTP headers before REMOTE_ADDR. A remote unauthenticated attacker can supply an allowed address in one of these headers to impersonate a trusted client and access exposed hostname, kernel, CPU, memory, filesystem, and network-interface information. This issue is fixed in version 3.4.6.",
  "id": "UBUNTU-CVE-2026-55584",
  "modified": "2026-08-31T00:00:00Z",
  "published": "2026-08-31T00:00:00Z",
  "references": [
    {
      "type": "REPORT",
      "url": "https://ubuntu.com/security/CVE-2026-55584"
    },
    {
      "type": "REPORT",
      "url": "https://www.cve.org/CVERecord?id=CVE-2026-55584"
    },
    {
      "type": "REPORT",
      "url": "https://github.com/phpsysinfo/phpsysinfo/security/advisories/GHSA-786w-p5pm-cvgh"
    },
    {
      "type": "REPORT",
      "url": "https://github.com/phpsysinfo/phpsysinfo/commit/019fa2d7e568ea11461adb4bd33da5dc87c4b9ab"
    },
    {
      "type": "REPORT",
      "url": "https://github.com/phpsysinfo/phpsysinfo/commit/019fa2d7e568ea11461adb4bd33da5dc87c4b9ab"
    },
    {
      "type": "REPORT",
      "url": "https://github.com/phpsysinfo/phpsysinfo/releases/tag/v3.4.6"
    }
  ],
  "related": [],
  "schema_version": "1.7.0",
  "severity": [
    {
      "score": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N",
      "type": "CVSS_V3"
    },
    {
      "score": "medium",
      "type": "Ubuntu"
    }
  ],
  "upstream": [
    "CVE-2026-55584"
  ]
}

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

CVE-2026-55584 (GCVE-0-2026-55584)

FKIE_CVE-2026-55584

GHSA-786W-P5PM-CVGH

Summary

Affected component

Description

Proof of Concept

Impact

Remediation

Discovery / Credit

ubuntu-cve-2026-55584

Vulnerability from osv_ubuntu

Tags

Sightings

Nomenclature