CyberSecBulletin
CVE-2024-4577Exploited in the wildNVD status: Analyzed

PHP-CGI OS Command Injection

Published Updated By the CyberSecBulletin desk

CVE-2024-4577 is a critical-severity improper neutralization of special elements used in an OS command vulnerability in PHP from PHP Group, with a CVSS 3.1 base score of 9.8 out of 10. It can be exploited remotely over the network by an unauthenticated attacker, without any action from a user. The record lists versions 8.1.29, 8.2.20, 8.3.8 as the first without the flaw, so updating PHP to one of those releases or later removes the exposure. CISA added it to the Known Exploited Vulnerabilities catalogue on June 12, 2024, which means attacks have been observed in the wild, including in ransomware campaigns.

Patch now

Attackers are already exploiting this vulnerability, according to CISA.

What to do

  1. Update PHP to 8.1.29 or 8.2.20 or 8.3.8, whichever matches your release line, or a later version.
  2. CISA's required action: Apply mitigations per vendor instructions or discontinue use of the product if mitigations are unavailable.
  3. Read the advisory on github.com for workarounds and exact fixed builds.
  4. Until you can update, restrict network access to the affected service so it is not reachable from untrusted networks.

Affected products and versions

VendorProductAffected versionsFixed in
PHP GroupPHP8.1.* up to, but not including, 8.1.29; 8.2.* up to, but not including, 8.2.20; 8.3.* up to, but not including, 8.3.8; 8.1.0 up to, but not including, 8.1.29; 8.2.0 up to, but not including, 8.2.20; 8.3.0 up to, but not including, 8.3.88.1.29, 8.2.20, 8.3.8
Fedora ProjectFedora39; 40Not stated

Version data comes from the organisation that assigned the CVE. Confirm against the vendor advisory before deciding you are unaffected.

How the severity score breaks down

Attack vector
NetworkCan be exploited remotely over a network, including the internet.
Attack complexity
LowNo special conditions are needed; the attack works reliably.
Privileges required
NoneNo account or login is needed.
User interaction
NoneNo action by a victim is required.
Scope
UnchangedImpact stays within the vulnerable component.
Confidentiality
HighAll data handled by the component can be read.
Integrity
HighData or code can be modified at will.
Availability
HighThe component can be taken down completely.

Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H. Scored by NVD.

Scoring systemScoreSeverityScored by
CVSS 3.19.8CriticalCNA (php.net)
CVSS 3.19.8CriticalNVD

Official description

In PHP versions 8.1.* before 8.1.29, 8.2.* before 8.2.20, 8.3.* before 8.3.8, when using Apache and PHP-CGI on Windows, if the system is set up to use certain code pages, Windows may use "Best-Fit" behavior to replace characters in command line given to Win32 API functions. PHP CGI module may misinterpret those characters as PHP options, which may allow a malicious user to pass options to PHP binary being run, and thus reveal the source code of scripts, run arbitrary PHP code on the server, etc.

Source: the CVE record as published by its numbering authority, via NVD and CVE.org.

The underlying weakness: Improper Neutralization of Special Elements used in an OS Command

The product constructs all or part of an OS command using externally-influenced input from an upstream component, but it does not neutralize or incorrectly neutralizes special elements that could modify the intended OS command before it is sent to a downstream component.

How developers prevent this class of flaw

  • If at all possible, use library calls rather than external processes to recreate the desired functionality.
  • For any data that will be used to generate a command to be executed, keep as much of that data out of external control as possible. For example, in web applications, this may require storing the data locally in the session's state instead of sending it out to the client in a hidden form field.
  • For any security checks that are performed on the client side, ensure that these checks are duplicated on the server side, in order to avoid CWE-602. Attackers can bypass the client-side checks by modifying values after the checks have been performed, or by changing the client to remove the client-side checks entirely. Then, these modified values would be submitted to the server.

More Improper Neutralization of Special Elements used in an OS Command vulnerabilities (CWE-78)

Timeline

  1. CVE record published.
  2. Added to CISA's Known Exploited Vulnerabilities catalogue.
  3. CISA published its SSVC assessment (exploitation: active, automatable: yes, technical impact: total).
  4. Deadline for US federal agencies to remediate, set by CISA.
  5. Record last changed materially (score, affected products, status or references).

References

Technical write-ups (may include proof of concept)

Other vulnerabilities in PHP

All PHP vulnerabilities

Recent Improper Neutralization of Special Elements used in an OS Command vulnerabilities

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