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Actively exploited

CVE-2012-1823 PHP-CGI Query String Parameter Vulnerability

sapi/cgi/cgi_main.c in PHP, when configured as a CGI script, does not properly handle query strings, which allows remote attackers to execute arbitrary code.

From the CISA KEV catalogue version 2026.11.06, with Cybergen analysis. Updated 6 Nov 2026.

Our Assessment

Should You Worry?

Patch nowCybergen assessment
  • CISA confirmed exploitation in the wild and added it to the Known Exploited Vulnerabilities catalogue on 25 Mar 2022.
  • Rated Critical severity (CVSS 9.8, scored by CISA).
  • It has been in the catalogue for 1,687 days. Systems still unpatched now have almost certainly been scanned for it.
The Vulnerability

What It Is

sapi/cgi/cgi_main.c in PHP before 5.3.12 and 5.4.x before 5.4.2, when configured as a CGI script (aka php-cgi), does not properly handle query strings that lack an = (equals sign) character, which allows remote attackers to execute arbitrary code by placing command-line options in the query string, related to lack of skipping a certain php_getopt for the 'd' case.

From Watch to Action

What To Do Now

  1. 1

    Find it

    Search your asset inventory and external attack surface for PHP. Include cloud images, appliances and anything a supplier runs for you.

    Attack Surface Management
  2. 2

    Fix it

    Apply updates per vendor instructions.

    Vulnerability Management
  3. 3

    Hunt for compromise

    If an affected system was reachable before you patched, assume it may have been hit. Check logs, new accounts, web shells and outbound connections from the date of exposure.

    Incident Response
  4. 4

    Prove it is fixed

    Rescan or test the system after patching. Upgrades that fail silently and forgotten secondary instances are common.

    Penetration Testing

Vendor Advisories

Regulation

The Compliance Clock

Cyber EssentialsRated critical, so if it affects devices in your Cyber Essentials scope, the update must be installed within 14 days of the vendor releasing it.NIS2If exploitation causes a significant incident, essential and important entities owe their CSIRT an early warning within 24 hours and a notification within 72 hours.DORAFinancial entities must classify ICT incidents and send an initial notification for a major incident within strict deadlines, with exploited flaws a common cause.US federal (BOD 22-01)Federal civilian agencies had until 15 Apr 2022 to remediate. A sensible benchmark for everyone else.

General guidance, not legal advice. Your obligations depend on your sector, scope and jurisdiction.

Stay Ahead

More Exploited PHP Flaws

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CVE-2016-10033PHPMailer Command Injection VulnerabilityAdded 7 Jul 2025CVE-2019-11043 · RansomwarePHP FastCGI Process Manager (FPM) Buffer Overflow VulnerabilityAdded 25 Mar 2022

All 3 exploited PHP vulnerabilities

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Evidence

Sources

  1. CISA Known Exploited Vulnerabilities catalogue
  2. NVD: CVE-2012-1823
  3. CVE record: CVE-2012-1823
  4. FIRST EPSS
  5. marc.info/?l=bugtraq&m=134012830914727&w=2
  6. lists.opensuse.org/opensuse-security-announce/2012-05/msg00011.html
  7. securitytracker.com/id?1027022
  8. h20000.www2.hp.com/bizsupport/TechSupport/Document.jsp?objectID=c03360041
  9. mandriva.com/security/advisories?name=MDVSA-2012:068
  10. lists.opensuse.org/opensuse-security-announce/2012-05/msg00002.html
  11. rhn.redhat.com/errata/RHSA-2012-0546.html
  12. rhn.redhat.com/errata/RHSA-2012-0568.html