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CVE-2026-109618 and CVE-2026-109619 represent two severe use-after-free vulnerabilities embedded within the PHP core engine.
These flaws specifically target the session upload progress handler when processing incoming multipart form data requests.
An unauthenticated remote attacker can trigger the vulnerability by sending a malicious HTTP POST request to any reachable PHP endpoint.
This includes default files, maintenance scripts, and empty index pages without requiring authentication or upload forms.
The PHP interpreter parses multipart request bodies before application-level middleware or web firewall rules execute.
Improper handling of upload progress tracking strings leaves dangling pointers and half-initialized memory structures behind.
During request shutdown, memory allocators free these structures while active references persist across requests.
This creates a dangerous cross-request use-after-free condition where reused worker processes treat freed memory as live data.
By utilizing heap-shaping jitter and per-build offsets between destructor functions and call handlers, execution flow is hijacked.
Winning the heap race allows arbitrary code execution directly under the privileges of the PHP process user.
CVE-2026-109618 also functions as a memory disclosure vector, leaking heap data back through session cookies.
CVE-2026-109619 combines a fatal-error backtrace use-after-free with OPcache type confusion for stable exploitation.
Because the vulnerability resides in core language components, popular CMS platforms and web applications are exposed.
Default installations across mod_php, PHP-FPM, and CGI server architectures are vulnerable out of the box.
Emergency patches were released by the PHP security team following public disclosure leaks and circulating exploits.
Administrators must inventory all instances, apply official security updates, and implement temporary edge mitigations immediately.
DailyCVE Form:
Platform: PHP engine
Version: All branches
Vulnerability: Code execution
Severity: Critical risk
date: October 21
Prediction: October 21
What Undercode Say:
Here are the scanner and lab commands related to the analysis repository:
pipx install git+https://github.com/0xrsydn/php2shell-scan python3 -m php2shell_scan probe https://target-host/ python3 -m unittest discover -s tests nix shell nixpkgsphp nixpkgsnginx -c bash -c 'php-fpm -y lab/fpm.conf & nginx -c lab/nginx.conf -p lab' python3 lab/fuzz.py --n 200 --conc 4 ./lab/detonate.sh /path/to/poc.py
Exploit: (Educational Purposes!)
The exploit framework leverages custom multipart payload generation with specialized upload-progress parameter names and heap-shaping jitter. It probes target servers to identify build-specific offsets between internal zval pointers and execution functions. By sending malformed body structures that induce worker crashes or memory corruption, the exploit achieves precise heap manipulation. When the race condition succeeds, the server executes arbitrary shell commands supplied in the payload under the web server user context.
Protection: from this CVE
- Immediately apply the official PHP security release provided for supported active branches.
- Configure web servers to block unauthenticated multipart requests at the edge if patching is delayed.
- For Nginx, add conditional rules to reject multipart/form-data requests on PHP paths with HTTP 403.
- Monitor system process trees for unexpected shell spawns originating from PHP worker processes.
- Upgrade legacy or end-of-life PHP installations to supported versions immediately.
Impact:
Successful exploitation grants unauthenticated remote code execution with the privileges of the PHP worker process. This enables attackers to deploy persistent web shells, extract sensitive database credentials, pivot deeper into internal network infrastructure, and fully compromise underlying server systems.
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Sources:
Reported By: github.com
Extra Source Hub:
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