CVE-2026-55584 phpSysInfo: IP allowlist (PSI_ALLOWED) bypass via spoofed X-Forwarded-For / Client-IP headers
Remote attackers can bypass IP allowlists by spoofing headers to access sensitive system information in phpSysInfo.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Over the internet
- Victim action needed
- Not needed
- Fix
- Available
What is CVE-2026-55584?
CVE-2026-55584 is a high-severity authentication bypass vulnerability in phpsysinfo, published on 28 Aug 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.
Official description
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.
Weakness: CWE-290
Which versions are affected by CVE-2026-55584?
2 open source packages ship an affected version, including phpsysinfo/phpsysinfo.
| Package | Affected | Fixed in |
|---|---|---|
phpsysinfo/phpsysinfo Packagist | All versions | 3.4.6 |
phpsysinfo/phpsysinfo Packagist | All versions | 3.4.6 |
How do I fix CVE-2026-55584?
Upgrade phpsysinfo/phpsysinfo to 3.4.6 or later.
Upgrade, and rotate credentials and sessions that may have been exposed. More about Authentication bypass.
Is CVE-2026-55584 being exploited?
There is no known exploitation of CVE-2026-55584 in the wild and no public exploit code.
Public exploit code: 1 Exploit-DB entry and 1 proofs of concept on GitHub.
Sources
Also known as DEBIAN-CVE-2026-55584, GHSA-786w-p5pm-cvgh, UBUNTU-CVE-2026-55584.