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This page v1 written in site v0.3.0 on 22 October 2026 · history
40 words this story cannot avoid, each explained for someone who has never worked in security, and each in the sense it has in this story. On every other page, the first use of each of these words is underlined and links here.
A fix copied to an older version. PHP published source-only backports for 7.4, 8.0 and 8.1, with no official release.
When software is out of support, its maintainers usually stop fixing it. For php2shell the PHP project published the fix as source code for 7.4, 8.0 and 8.1 but no ready-to-install release, so anyone on those versions has to build it themselves or rely on a Linux distribution that does.
Content delivery network: a service such as Cloudflare or Akamai that sits in front of many websites, caching pages and filtering traffic.
A CDN keeps copies of a website's pages close to its visitors and screens the traffic on the way in. Because so much of the web sits behind a few CDNs, their firewall rules protected many sites before their owners did anything.
Computer Emergency Response Team: a national or sector body that coordinates the response to cyber incidents.
CERT-EU, CERT-FR, CERT.LV and JPCERT/CC are examples. They publish alerts, collect reports of attacks and advise organisations in their country or sector.
The US Cybersecurity and Infrastructure Security Agency.
CISA is the US federal agency responsible for civilian cyber defence. It told organisations to take PHP systems offline if they could not patch, and keeps the KEV catalog.
The five words this site uses for how far a claim can be trusted.
Confirmed: two or more primary sources agree, or the site counted it from a captured file. Reported: one party says so and nobody has contradicted it. Disputed: sources disagree, and both readings are shown. Contradicted: a primary source says otherwise. Unverified: even the outlet reporting it could not check it.
Keeping a flaw secret between the finders and the maintainers until a fix is ready, then publishing both at an agreed time.
The agreed time is the embargo. For php2shell it was set for 22 October at 14:00 UTC. The CVE numbers leaked on 20 October, so the release was moved forward a day. The leak page reconstructs how.
Common Vulnerabilities and Exposures: the public catalogue that gives each known security flaw a unique ID, such as CVE-2026-109618.
A CVE ID is a serial number for a security flaw, so that a vendor, a government agency and a journalist can be sure they are talking about the same bug. The format is CVE, the year the number was reserved, and a sequence number. This story has two: CVE-2026-109618 and CVE-2026-109619. Each has an official record that says what is affected and how severe it is.
Common Vulnerability Scoring System: a severity score from 0 to 10. Both flaws score 9.2, which is rated critical.
CVSS turns the technical details of a flaw (can it be reached over the internet, does the attacker need a password, what can they do afterwards) into one number from 0 to 10. Anything from 9.0 up is critical. Both php2shell flaws are 9.2 under version 4.0 of the scale. The leaked early reports said 10.0, which was wrong.
Common Weakness Enumeration: a catalogue of kinds of software weakness (the bug class), as opposed to CVE, which names one flaw.
Where a CVE names one specific flaw, a CWE names the type of mistake behind it, such as use-after-free (CWE-416). The php2shell records list five.
A version the maintainers no longer fix. PHP 8.1 and older are end of life.
Software versions have a support window. After it ends, security fixes stop. PHP 8.1 and older are past theirs, so for organisations still on them php2shell is a migration project rather than an update.
The European Union Agency for Cybersecurity.
ENISA coordinates the EU's network of national response teams. Its advice on php2shell is one of the sixteen compared on the agencies page.
This site's private, encrypted store of every source it captured, each file hashed at the moment of capture.
Every page this site cites was saved, as served and as rendered, with a screenshot, into an encrypted vault. The pages themselves are not republished (they belong to their authors), but their fingerprints (hashes) are, so anyone can later check that nothing was changed.
To exploit a flaw is to actually use it in an attack. Exploitation attempts are tries; a compromise is a success.
An exploit is the code or technique that turns a vulnerability into an attack. This site keeps three things apart: an exploit existing, attempts being seen (requests that look like the attack), and a confirmed compromise (a named system actually broken into). For php2shell, the first two are reported; the third has not been confirmed anywhere as of the latest capture.
The security advisory the PHP project published on GitHub, with an ID starting GHSA. The most detailed primary record.
The PHP project publishes its security advisories on GitHub. Each has a GHSA identifier alongside its CVE. The two php2shell advisories carry the technical detail, the credits and the PHP team's own account of what was demonstrated.
A fingerprint of a file: change one byte and the hash changes, so a published hash proves later that a capture was not edited.
A SHA-256 hash is a 64-character fingerprint computed from a file's contents. Two different files practically never share one. Publishing the hash of every capture is how this site lets readers check its evidence without republishing other people's pages.
A decoy system set up to attract and record attacks.
A honeypot looks like a real, vulnerable server and exists only to be attacked, so its owner can see what attackers are trying. Amazon reports one was hit with a php2shell-shaped request four days before disclosure.
CISA's public list of flaws with reliable evidence of exploitation in the wild. Neither php2shell CVE was on it at the latest capture.
The Known Exploited Vulnerabilities catalog is maintained by the US agency CISA. A flaw goes on it when CISA has reliable evidence attackers are using it. It is the closest thing to an official, dated record of 'this was exploited', which is why this site checks it.
A C function that jumps out of the middle of running code without tidying up. PHP used it to abort on out-of-memory; the fix removes that.
longjmp is a low-level C mechanism for leaving a function in a hurry. It is fast and it skips cleanup, which is exactly the problem: PHP used it when a request ran out of memory, and the half-finished state it left behind is what the first flaw abuses.
PHP running inside the Apache web server. The setup where a complete exploit was demonstrated; php.net ranks it highest risk.
mod_php loads PHP directly into the Apache web server process. It is the oldest and simplest way to run PHP, still common on shared hosting, and the one the researchers exploited end to end before any application code ran.
The format a browser uses to send a form with a file upload. Limiting multipart requests is one of the stopgaps.
When you attach a file to a web form, the browser sends a multipart request. One of the demonstrated attack paths rides on PHP's handling of such requests, which is why some agencies suggest blocking or monitoring them at the edge where uploads are not needed.
National Cyber Security Centre: the name of the national cyber agency in the UK, the Netherlands (NCSC-NL) and New Zealand.
Several countries call their national cyber agency the NCSC. On this site NCSC UK, NCSC-NL and NCSC New Zealand are kept apart, because they gave different advice.
The US National Security Agency, whose cybersecurity arm issues advice to defenders.
The NSA's cybersecurity directorate publishes advice to US defence and critical-infrastructure organisations. Its post on X telling organisations that could not patch to take systems offline was one of the most widely shared pieces of advice in the story.
What happens when a program tries to use more memory than it is allowed. One flaw is in how PHP handles this.
PHP sets a memory limit for each request. When a request hits it, PHP abandons the request. The first flaw (CVE-2026-109618) is that this abandonment could leave memory half set up, and the cleanup that follows could be steered by an attacker.
An update that fixes a flaw. For PHP it means installing a fixed version and restarting PHP.
A patch is the fix. For php2shell the fixed versions are PHP 8.5.12, 8.4.27, 8.3.36 and 8.2.35, or a Linux distribution's updated package. Installing it is not enough on its own: PHP has to be restarted (and containers rebuilt) before the running server is actually fixed.
A programming language that runs on web servers and builds the pages you see. WordPress, Drupal and Wikipedia's software are written in it.
PHP is the language a large share of websites are written in. When you open a WordPress blog or a council website, a program on the server written in PHP builds the page and sends it to your browser. You never install PHP on your phone or laptop; it lives on the server. That is why this story is about websites and the organisations that run them, not about personal devices.
PHP running as a separate pool of worker processes behind a web server such as nginx. Susceptible; whether a full exploit exists is disputed.
FPM (FastCGI Process Manager) is the most common modern way to run PHP behind nginx or a load balancer. The PHP project says FPM is susceptible; the two primary accounts differ on whether a complete exploit against it for the first flaw has been demonstrated.
The nickname for these two flaws: from PHP to a shell, meaning an attacker can get a command line on the web server.
Security flaws with a big impact get nicknames so people can talk about them (Heartbleed, Shellshock, Log4Shell). php2shell reads as PHP to shell: send a request to a PHP website, and come away with a shell, a command line on the server. The NSA wrote it PHP2Shell. The official names are the two CVE numbers.
The party's own words: the CVE record, the vendor's advisory, the agency's page. Not a news report about them.
This site prefers primary sources and marks every source as primary or secondary. A claim that rests only on a news report is shown as reported until the original is found and captured.
Code that shows a flaw can really be exploited. A public PoC makes attacks easier for others.
Researchers write a proof of concept to convince the maintainers a bug is real. If it leaks or is published, less skilled attackers can reuse it. Several published php2shell PoCs reportedly do not work as published.
An attacker on the internet can make the server run commands of their choosing. The most serious kind of flaw.
Remote code execution means someone who is not on your network, and may be on the other side of the world, can make your computer run their instructions. On a web server that usually means they can read what the website can read (its files, its database passwords) and use the server as a foothold. It is the worst outcome a single flaw can have, which is why the agencies reacted as they did.
Server API: the way PHP is plugged into the web server. Which one is used changes how exposed a site is.
PHP can be attached to a web server in several ways: inside Apache (mod_php), as a separate pool of workers (PHP-FPM), as CGI, or through newer servers such as FrankenPHP. Each is a SAPI. The full exploit was shown against mod_php; the others are susceptible to different degrees.
Software bill of materials: a list of the components inside a piece of software.
An SBOM is the ingredient list for software. With one, an organisation can answer 'do we use PHP, and which version' in minutes instead of days, which is the first question this incident asked.
A command line on a computer. Getting a shell on a server means being able to type commands on it.
A shell is the text window where an administrator types commands. An attacker who gets a shell on a web server can run commands with whatever permissions the web server program has. It is where the nickname php2shell comes from.
No login needed: anyone who can reach the website can try the attack.
Many flaws need the attacker to have an account first. An unauthenticated flaw does not: the attacker only needs to be able to send a request to the website, which for a public site means anyone on the internet.
A memory bug where a program keeps using memory after releasing it, so an attacker can control what is found there.
When a program frees memory it promises not to use it again. If it does anyway, whatever was put there since (possibly by an attacker's request) is read as if it were trusted. The second flaw (CVE-2026-109619) is of this kind, across two requests handled by the same worker.
Vulnerability Exploitability eXchange: a vendor's statement of whether its product is affected by a given flaw.
A VEX statement lets a vendor say 'our product contains PHP but is not affected', or 'is affected, fixed in version X'. The Dutch NCSC inventory is built from them.
A flaw in software that an attacker can use to make it do something it should not.
Every large program has bugs. A vulnerability is a bug with a security consequence: it lets someone read what they should not, change what they should not, or run their own code. This site uses vulnerability and flaw for the same thing.
Web application firewall: a filter in front of a website that blocks requests that look like attacks. A stopgap here, not a fix.
A WAF inspects every request before it reaches the website and drops the ones that match known attack patterns. Cloudflare, Akamai, Fastly, Imperva, AWS and others shipped rules for php2shell, some before the fix was public. Every one of them says the same thing: it buys time, it does not replace patching.
The computer, and the program on it, that answers when a browser asks for a page. PHP runs there, not on your device.
When you type an address into a browser, a web server somewhere receives the request and sends back the page. For PHP websites, the web server hands the request to PHP, which builds the page. Both flaws are reached by sending that server a specially crafted request.
The core of PHP, written in C, that runs PHP code. Both flaws are here, below every PHP application.
The Zend engine is the part of PHP that reads PHP code and executes it, manages memory and handles errors. Because the flaws are in the engine, it does not matter how well the website's own code is written: any site on an unpatched PHP is in scope.