The PHP project released patches Wednesday for two critical vulnerabilities in a programming language used in an extremely large portion of the internet.

The patch addresses two flaws, catalogued as CVE-2026-109618 and CVE-2026-109619, both rated 9.2 on the CVSS v4.0 severity scale, which tops out at 10. Researchers describe them as remote code execution vulnerabilities, which could let an attacker run their own code on a server and potentially take control of it. 

The vulnerabilities have been dubbed “php2shell” by researchers. While the industry has spent the past 24 hours sounding the alarm over the vulnerabilities, there has been very little in terms of reported exploitation as of Wednesday afternoon.

In a release, the Cybersecurity and Infrastructure Security Agency said it wasn’t aware of any exploitation.

“While CISA has not observed exploitation of these vulnerabilities as of the time of publication, they pose a risk to organizations if left unpatched,” the release reads.

Multiple researchers have told CyberScoop that they have observed very little activity outside of reconnaissance that is probing to see what vulnerable systems are still connected to the internet.

“We see clear evidence attackers are actively probing and performing reconnaissance across PHP applications,” Kelly Shortridge, chief product officer at Fastly, told CyberScoop. “The gap between disclosure and widespread, repeatable exploitation is typically hours to a few days for vulnerabilities of this severity and attack ROI.”

“We have not observed, or independently confirmed, successful in-the-wild exploitation of these vulnerabilities on live customer systems,” Jon Semon, principal security operations analyst at Huntress, told CyberScoop.

“We have checked across the Linux web servers we have visibility into for the post-exploitation behavior shown in the public proof of concept, such as a web server process spawning a shell that runs recon commands or writes a file into the web root, and did not find activity matching it.”

Neither the technical cause nor a complete list of affected versions has been officially confirmed, with the PHP team saying full details will be published with the release. An advisory from CERT-EU, the European Union’s computer emergency response team, says the flaws could affect every version of PHP from 5 onward. 

The security firm watchTowr said Tuesday the vulnerabilities had been set for release Thursday under embargo. The PHP team moved the release up a day and said it could act sooner still if details became public or exploitation appeared.

A video demonstrating an exploit chain spread online overnight via researcher Kirill Firsov, who shared it and credited researchers known as LCFR and Calif.io. watchTowr said it had reproduced one of the flaws. Code claiming to exploit the flaws is circulating but has not been verified, and security firms caution such code is sometimes laced with malware.

The potential exposure is broad. PHP runs between 70-80% of websites whose server-side language is known, according to market research, and underpins platforms including WordPress, Drupal, Joomla and Laravel. Researchers estimated more than 1.3 million internet-exposed hosts could be vulnerable, and a Shodan search counted about 1.9 million. Among servers that disclose their version, most run branches are no longer receiving security updates: about 758,000 run versions from 5.4 through 8.1, compared with 272,000 on supported branches, according to VirusTotal.

CERT-EU and Britain’s National Cyber Security Centre advised organizations to prepare to update systems quickly and suggested isolating internet-facing applications where immediate patching was not feasible. PHP flaws have been exploited before: the U.S. Cybersecurity and Infrastructure Security Agency’s known-exploited vulnerability catalog lists three in PHP itself, two used in ransomware campaigns.

The vulnerability was discovered by AI cybersecurity firm Calif, using OpenAI’s cybersecurity-focused AI model GPT-5.6 Sol. Wiz, an AI security firm purchased by Google in March, also independently discovered and reported the flaw, according to a blog posted by OpenAI on Wednesday.

The discovery sparked a two-month collaborative effort between OpenAI, PHP maintainers, researchers and security providers to develop a long-term technical fix and prepare for public disclosure.

OpenAI said the priority for all organizations relying on PHP is to apply the new patches, and offered a free tool and other support to help identify vulnerable versions.

“To our knowledge, frontier AI found these vulnerabilities before attackers did, opening a Defender’s Window for maintainers and security providers to prepare fixes and protections ahead of disclosure,” OpenAI wrote in an unsigned blog.

OpenAI also said the PHP flaw is among “several significant vulnerabilities we’ve already found and are working to fix, and we expect similar findings to increase sharply in the coming months.”

In a blog posted the same day, researchers at Wiz said they had discovered “multiple critical vulnerabilities” in PHP, all related to memory safety using GPT-5.6 Sol, their own Wiz Atlas AI tool and Google’s Gemini 4 Argon to conduct their research.

Perhaps most concerning: The bug existed for decades prior to the emergence of modern AI tools, but it’s so complex and technically arduous that few attackers were likely capable of exploiting it.

According to Wiz, it required developing exploits for “notoriously complex” memory bugs that work across different PHP versions, configurations and application behaviors. It would also have to account for differences in PHP deployments that could render the exploit harmless, and each change would require more testing, analysis and debugging.

In the era of AI hacking, “this is no longer a barrier,” the Wiz researchers said.

Large language models can adapt exploits to different PHP versions, configurations or memory layouts, use third-party testing and debugging tools, and carry out a series of other functions for “reducing the specialist effort required for each target.”

“This changes the economics of both discovery and exploitation,” wrote Wiz researchers Sagi Tzadik, Shir Tamari, Nir Ohfeld and Tomer Schwartz. “As AI reduces the effort needed to develop and adapt complex exploits, vulnerabilities that once seemed impractical to exploit become viable targets.”

More information is expected over the course of the day. The PHP team is to publish the full advisory with the release, and security firms including Huntress and Tenable said they would update their analyses as technical details and proof-of-concept code emerge.

UPDATE: 10/21/2026, 3:00 p.m. ET: This article was updated to include infromation from CISA and from industry researchers.

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A cybersecurity working group at the G7 is urging governments to accelerate defenses against quantum computers that could break some existing forms of public key encryption.

The working group’s report, prepared in June at the G7 Summit in France, said organizations “can no longer afford to postpone” work transitioning critical systems and data to “post-quantum” forms of encryption.

“The quantum threat remains off the radar for many organizations and not properly resourced, with other security concerns taking precedence,” the working group report said. “Yet, a successful and collective transition to PQC can only be achieved if organizations understand that the quantum threat is an economic and business risk, and not merely a cryptographic risk.”

Instead, leaders in government and industry “must reframe the quantum threat from a distant future problem to a near-term threat that demands action across all sectors, not just critical infrastructure.”

The report acknowledged uncertain timelines for quantum computers, but identified that threats like harvesting current sensitive, encrypted data to decrypt it in the future do exist today.

The report also warned that quantum computers could compromise authentication and assurance mechanisms—by forging trusted data or stealing confirmation— jeopardizing secure communications and legal contracts.

The working group’s conclusions are largely in line with what governments have been recommending for years, urging industry to inventory and prioritize their critical systems and shift over to newer, “post-quantum cryptography” encryption algorithms.

These encryption algorithms, originally designed by independent cryptographers and vetted by the National Institute for Standards and Technology and National Security Agency, will be used to protect the government’s own systems and data from cybercriminals and foreign governments.

The Trump administration recently issued an executive order directing agencies to boost the domestic quantum industry and move up internal timelines for migrating to PQC encryption from 2035 to 2030. Google, a potential industry bellwether, and other companies have opted to move their own migration timelines to 2029.

But while that work has proceeded on schedule in some areas, like the federal government and the highly regulated financial sector, it has lagged in other industries where owners and operators feel they have more immediate concerns than quantum computers.

“We acknowledge that transitioning to PQC is not a problem for individual organizations to solve in isolation, but rather a collective transition that can only be achieved with early engagement, coordinated planning and informed decision making across the public and private sectors,” the working group wrote.

While often referred to as “Post-Quantum” encryption, the reality is more complex. Cryptographers believe the algorithms selected by NIST and NSA will stand up to attacks from a quantum computer, but since one doesn’t exist today, designing cryptographic protections against it requires some guesswork and mathematical estimation.

Estimates can be wrong, or overlook the entire cryptographic attack surface. Some NIST-selected algorithms have already been broken with traditional computers or AI. That’s why the agency backs multiple algorithms and concepts like “crypto-agility,” allowing organizations to quickly switch between them.

The G7 report was signed by the U.S. Cybersecurity and Infrastructure Security Agency (CISA), the UK’s National Cyber Security Centre (NCSC), The French Cybersecurity Agency (ANSSI), Germany’s Federal Office of Information Security (BSI), Canada’s Communications Security Establishment (CSE), Japan’s National Cybersecurity Office (NCO) and Italy’s National Cybersecurity Agency (ACN).

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