AI Found A PHP Bug That Puts Up To 70% Of Websites At Risk: What php2shell Is, Who's Affected, And How To Patch It

On Wednesday, October 21, 2026, the PHP Foundation disclosed two critical flaws, nicknamed php2shell, that let attackers run code on unpatched PHP servers without logging in. PHP is the language behind WordPress and a large share of the web, and AI models helped find a bug that had been sitting in it for 14 years.

Within hours, government agencies in Europe pulled websites offline, Cloudflare reported early attack attempts, and the FBI and NSA urged organizations to update. The patch exists. The open question is how fast the internet applies it.

What php2shell Actually Is

php2shell is the collective name for two critical vulnerabilities in PHP itself, CVE-2026-109618 and CVE-2026-109619, each rated 9.2 out of 10 on the CVSS severity scale. Because the flaws live in the language, not in any one website or plugin, updating WordPress, a theme, or an extension does not fix them. Only a patched PHP does.

How AI Found It

Three groups reached the same flaw independently in August 2026, and all of them used AI to do it. They then joined a coordinated effort with the PHP Foundation to develop fixes and time the disclosure, led by OpenAI.

OpenAI president Greg Brockman noted that the underlying bug had been present for 14 years, and that a limited version of it surfaced in 2024 but wasn't considered significant at the time. The Calif team said it wasn't expecting to find anything critical, since PHP has been scrutinized by the security community for years.

Where The "70%" Comes From, And What It Doesn't Mean

The 70% figure is an estimate of how much of the web runs on PHP, not a count of websites confirmed to be vulnerable. Coverage from CNN, The Washington Post, and Fortune uses the phrase "up to" or "as much as" 70% for that reason: it describes the maximum exposed population before anyone patches.

• PHP powers WordPress, which Reuters says runs roughly 40% of all websites, along with many other content systems and a long tail of custom applications

• Whether a particular site is exposed depends on its PHP version, its configuration, and whether the fix has been applied

• Palo Alto Networks' initial scan put the number of potentially vulnerable instances at about 22.6 million, a much narrower figure than 70% of the web

• Wiz has compared the severity to the 2014 Heartbleed bug, which affected an encryption library used by roughly two-thirds of the web

What Happened On Disclosure Day

The response was fast and, in places, disruptive: several government and company sites went dark as a precaution while administrators updated.

• Government agencies in the Netherlands and Finland took websites offline, and an EU agency warned others might need to, according to Reuters

• The Internet Archive's Archive.org went temporarily offline

• The FBI's Cyber Division and the NSA urged potentially affected organizations to update, as did the EU's computer emergency response team and Japan's prime minister

• Cloudflare's CTO said the company was seeing early attack attempts, and Cloudflare rolled out initial firewall rules for the known exploit routes

Successful breaches were still described as limited as of Thursday, with a handful of unverified individual reports circulating online. Security vendors say exploitation attempts have been observed in the wild, which is why most of them are treating this as a patch-now situation rather than a watch-and-wait one.

Why Researchers Call It An "AI Inflection Point"

The flaw itself wasn't new, what changed is how fast AI can turn a subtle weakness into a working attack. Wiz said the vulnerable code had been in PHP for more than a decade, and that AI's contribution was the ability to understand the weaknesses and turn them into an exploit. OpenAI called it one of the most impactful security issues in recent memory.

What Site Owners Should Do Now

The only complete fix is updating PHP to a patched release and restarting the processes that serve your site. This guidance reflects advisories from the PHP project and security vendors as of October 22, 2026, so check your host's or the PHP project's current notices for updates.

• Update PHP to 8.5.12, 8.4.27, 8.3.36, or 8.2.35, whichever branch you're on

• Restart your PHP workers (PHP-FPM, Apache, or container workers) after updating. A package update alone doesn't replace code already loaded in memory

• Don't rely on a WordPress update. The fix has to happen in the PHP your host or server runs, so confirm the exact PHP version with your host

• Using PHP 8.1 or older? There's no upstream release. Upgrade to a supported branch, get a backported fix from your Linux distribution or vendor, or take the system offline until it's patched, which is the guidance security firms attribute to CISA for systems that can't be updated

• Rebuild container images and redeploy, since a base image is only as fixed as its last rebuild

• Review logs from before you patched for signs of suspicious requests

If an immediate update isn't possible, some vendors, including Aikido, have published stopgap configuration changes to reduce exposure, which they stress should be applied together at the server level and are not a substitute for patching. Sites behind Cloudflare also benefit from its initial protective rules, but those too are a layer, not a cure. PHP 8.2, one of the patched branches, reaches end of life on December 31, 2026, so it's worth planning a move to a newer branch.

The Same Capability Cuts Both Ways

php2shell lands in the middle of an ongoing argument about whether AI helps defenders or attackers more, and the evidence so far says both. Fortune reported the same day on a growing wave of AI-assisted cyberattacks, and Forbes recently reported on a hacker who used Anthropic and DeepSeek models to steal more than 600,000 credit card numbers in attacks on over 100 websites.

It also connects directly to a threshold covered elsewhere on this site. OpenAI's newer Astra model was the first the company classified at its "Critical" cybersecurity tier, and GPT-5.6 Sol, the model at the center of the php2shell discovery, was the model that preceded it in the "High" tier. This week's disclosure is a concrete example of the capability those risk categories were created to describe, used here for defense, and a reminder that the same skills don't stay on one side of the line.

The php2shell PHP Vulnerability: FAQ

This article summarizes public reporting on a fast-moving security incident as of October 22, 2026. It is general information, not a substitute for guidance from the PHP project, your hosting provider, or your organization's security team.

Jans Bock-Schroeder

Publisher & Founder of AI Angst

Coming from the world of art, photography, and the luxury market, Jans launched AI Angst in 2025 to explore the cultural, ethical, and psychological impacts of artificial intelligence. His work bridges creative vision with critical technology analysis, offering clarity in an era of rapid technological change.