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

Exploitation

No confirmed exploitation recorded. Patch Next marks exploitation only from CISA KEV.

CVSS

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

EPSS

• CVE-2026-55584: 1.91% estimated exploitation activity in the next 30 days; percentile 79.81 (FIRST EPSS, 2026-11-03). This is a model estimate, not proof of exploitation or customer exposure.

As published by the source; long descriptions are shortened.

Summary phpSysInfo's PSIALLOWED IP allowlist can be trivially bypassed by any unauthenticated remote attacker. The access-control check in readconfig.php derives the client IP from the attacker-controlled X-Forwarded-For and Client-IP HTTP headers before falling back to REMOTEADDR. 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: readconfig.php - Versions: all versions up to and including 3.4.x (current main) Description When PSIALLOWED is configured, readconfig.php enforces an IP allowlist. The client IP is resolved as follows: Both HTTPXFORWARDEDFOR and HTTPCLIENTIP are fully attacker-controlled request headers. They are trusted unconditionally and take priority over REMOTEADDR. There is no concept of a configured/trusted reverse proxy, so even when phpSysInfo is exposed directly (no proxy in…

Published by the source

28 Aug 2026, 18:30 UTC

Last modified by the source

28 Aug 2026, 18:55 UTC

Source last checked

26 Oct 2026, 14:50 UTC

1. Revision 2 · amended · 26 Oct 2026

   Amended from ghsa record GHSA-786w-p5pm-cvgh

2. Revision 1 · created · 24 Oct 2026

   Published from osv record GHSA-786w-p5pm-cvgh

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# Patch Next advisory brief: CVE-2026-55584

Advisory: phpSysInfo has an IP allowlist (PSI_ALLOWED) bypass via spoofed X-Forwarded-For / Client-IP headers
IDs: CVE-2026-55584, GHSA-786w-p5pm-cvgh
Record: https://patchnext.com/advisories/cve-2026-55584 (revision 2, source checked 26 Oct 2026, 14:50 UTC)
Inventory: none attached. This brief comes from a public page and does not say whether any deployment is affected.
Severity: High (CVSS 7.5)
Exploitation: no confirmed exploitation recorded. Patch Next confirms exploitation only from CISA KEV.
Vendor response: Vendor fix available; fixed versions by package: phpsysinfo/phpsysinfo 3.4.6. A vendor fix does not mean a deployment is fixed.

## Affected components
- Packagist phpsysinfo/phpsysinfo: affected <= 3.4.5; fixed in 3.4.6

## Suggested inspection (read-only)
- Packagist phpsysinfo/phpsysinfo: check the installed version with your package manager.

## Supported action
Upgrade each affected component to a fixed version on its release line. For a transitive dependency, upgrade the parent package or add an override or constraint, then regenerate the lockfile. Redeploy every environment that ran an affected version.

## Required regression checks
- Run the test suite and a production build.
- Exercise the features that depend on phpsysinfo/phpsysinfo.
- Repeat the inspection and confirm that only fixed versions remain installed.

## Rollback considerations
- Keep the previous lockfile and deployment artifact. Rolling back reinstates the vulnerable version, so apply any documented mitigation while you fix forward.

## Unresolved questions
- Which deployments run an affected version?
- Exploitation status can change. Check again before lowering the priority.
- Mark the work resolved only after the fixed version is verified in production.

## Sources
- Verified: https://osv.dev/vulnerability/GHSA-786w-p5pm-cvgh (OSV record GHSA-786w-p5pm-cvgh lists affected ranges: Packagist phpsysinfo/phpsysinfo >=0 <3.4.6 (fixed))
- Verified: https://github.com/advisories/GHSA-786w-p5pm-cvgh (GitHub-reviewed advisory GHSA-786w-p5pm-cvgh lists affected ranges: Packagist phpsysinfo/phpsysinfo >=0 <=3.4.5)

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