CVE-2026-109618 PHP Group · PHP

PHP - Remote Code Execution via Out-of-Memory Corruption

Vulnerability at a glance

Severity, exploitation likelihood & attack requirements

CVSS v4.0 severity
9.2Critical
EPSS · exploitation likelihood
Not available No score available
EPSS trend
UnavailableNo comparable history
Known exploitation
Not in KEV CISA KEV catalog Absence does not establish safety
Attack vector
NetworkRemotely reachable
Attack complexity
HighMore obstacles to exploitation
Privileges required
NoneNo authentication required
User interaction
NoneNo user action needed
Exploit availability & maturity
Not scored Availability not established No explicit exploit maturity assessment View exploit evidence
How to read the colors & trend
Higher exposureElevatedModerateLower exposureUnknown / unassessed

CVSS colors follow its reported severity. Attack-factor colors describe each requirement, not an overall risk rating. Gray also covers absence from KEV; absence does not establish safety.

EPSS display bands: below 1% blue, 1–10% amber, 10–50% orange, 50% and above red. These are presentation bands, not FIRST severity categories. The trend compares daily EPSS probabilities, not percentile ranks; “pp” means percentage points. The sparkline shows relative movement, with its vertical scale fitted to the observed scores.

Atomicorp ModSecurity protection

Protected by Atomicorp rules

Atomicorp ModSecurity rules block attacks exploiting this vulnerability when blocking is enabled. Keep your rules current.

4 rules identified View rules & research details →

WAF protection applies to the tested attack paths; it does not change the CVSS or EPSS score. Keep your software patched and your Atomicorp rules current.

CISA SSVC

No CISA SSVC assessment is available in the current source data.

On this page

CVE Details

  • Protection status: Protected by Atomicorp rules · About protection statuses
  • CVE: CVE-2026-109618
  • Name: PHP - Remote Code Execution via Out-of-Memory Corruption
  • Severity: Critical
  • CVSS: 9.2 (v4.0) (Critical)
  • CVSS version: 4.0
  • CVSS source: php CNA
  • CVSS vector: CVSS:4.0/AV:N/AC:H/AT:P/PR:N/UI:N/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X
    • Attack vector: Network
    • Attack complexity: High
    • Attack requirements: Present
    • Privileges required: None
    • User interaction: None
    • Vulnerable-system confidentiality: High
    • Vulnerable-system integrity: High
    • Vulnerable-system availability: High
    • Subsequent-system confidentiality: Negligible
    • Subsequent-system integrity: None
    • Subsequent-system availability: None
    • Safety: Not defined
  • CWE: CWE-416 — Use After Free, CWE-755 — Improper Handling of Exceptional Conditions, CWE-824 — Access of Uninitialized Pointer, CWE-1325 — Improperly Controlled Sequential Memory Allocation
  • Related CAPEC attack patterns (via MITRE CWE relationships): CAPEC-130
  • Vendor: PHP Group
  • Vulnerable product: PHP
  • CVE published: 2026-10-21
  • CVE last modified: 2026-10-21
  • Latest Update: 2026-10-21
  • Reviewed Rule IDs: 314143 , 330791 , 330793 , 340152
  • Reviewed rules with current blocking actions: 314143 , 330791 , 330793 , 340152
Technical vulnerability details · CVSS assessments, exploit evidence & CPE data

CVSS assessments

CVSS v4.0 · security@php.net

  • Base score: 9.2
  • Base severity: CRITICAL
  • Assessment type: Secondary
  • Source identifier: security@php.net
  • Full vector: CVSS:4.0/AV:N/AC:H/AT:P/PR:N/UI:N/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X
    • Attack vector: Network
    • Attack complexity: High
    • Attack requirements: Present
    • Privileges required: None
    • User interaction: None
    • Vulnerable-system confidentiality: High
    • Vulnerable-system integrity: High
    • Vulnerable-system availability: High
    • Subsequent-system confidentiality: Negligible
    • Subsequent-system integrity: None
    • Subsequent-system availability: None
    • Safety: Not defined
  • Exploit maturity: Not scored

Exploitability and impact subscores describe the vulnerability’s technical characteristics. Exploit maturity describes the reported state of exploitation; these are separate measures.

Assessment source: NVD record · CVE record

Vulnerable CPE configurations

No vulnerable CPE configurations are supplied in the current NVD record. See the affected-product information and vendor guidance on this page.

Vulnerability Description

PHP uses longjmp() for out-of-memory (OOM) errors to exit the current context and abort handling of the request. Some contexts may not properly account for this scenario and leave request memory in an uninitialized state before performing an allocation. The subsequent request cleanup procedure may read or branch on this memory. Multiple OOM strategies can consistently trigger this condition and lead to remote code execution (RCE).

  1. Maintain the reviewed Atomicorp rules. Keep your Atomicorp commercial rules current and confirm that the reviewed rules (314143 , 330791 , 330793 , 340152 ) have not been locally disabled. Atomicorp commercial rules are enabled by default. If you use Atomic WAF, review the applicable policy and rule settings.

  2. Apply the vendor’s remediation. WAF protection is defense in depth and does not replace upgrading or following the affected vendor’s guidance.

    • Affected versions: PHP Group PHP versions earlier than 8.2.35.
    • Affected versions: PHP Group PHP versions earlier than 8.3.36.
    • Affected versions: PHP Group PHP versions earlier than 8.4.27.
    • Affected versions: PHP Group PHP versions earlier than 8.5.12.
    • Recommended upgrade: Upgrade PHP Group PHP to 8.2.35 or later.
    • Recommended upgrade: Upgrade PHP Group PHP to 8.3.36 or later.
    • Recommended upgrade: Upgrade PHP Group PHP to 8.4.27 or later.
    • Recommended upgrade: Upgrade PHP Group PHP to 8.5.12 or later.
    • CNA guidance source: php
    • Vendor workaround: Check the GitHub Security Advisory for mitigation strategies.

  3. Validate after changes. Confirm rule updates are current, review WAF events for the affected application, and test application behavior after vendor upgrades, mitigations, or local policy changes.

Research Notes

Atomicorp WAF protections are designed around attack techniques and exploit behaviors, allowing existing protections to apply across multiple vulnerabilities without requiring a unique rule for every CVE.

Public Vulnerability References

Test or Research Source

  • Source: https://github.com/php/php-src/security/advisories/GHSA-w8hw-w9fx-j79w
  • Tags: manual-review
  • Research basis: Manual PHP core inspection established protection for the session upload-progress attack path using new Atomicorp rule 314143. Additional manual review identified existing rules 330791, 330793 and 340152 as disrupting other reviewed cases associated with this CVE.
  • Notes: New rule 314143 blocks requests carrying PHP’s default session upload-progress activation field. Existing rule 330793 enforces strict multipart validation; existing rules 330791 and 340152 reject request-body parsing errors. These existing controls disrupt additional reviewed request paths. Use current Atomicorp rules with blocking enabled and install the fixed PHP package for your branch. PHP lists fixes in 8.2.35, 8.3.36, 8.4.27 and 8.5.12; distribution packages may provide backported fixes.

Research Note Context

This research note documents exploit-technique analysis associated with this vulnerability and references Atomicorp WAF protections observed during engineering review, testing, or validation activities.

Atomicorp security controls are generally designed to identify and mitigate attack techniques and exploit behaviors rather than individual CVE identifiers. As a result, protections developed for one vulnerability may also apply to related attack variants and future vulnerabilities using similar techniques.

Learn More

Atomicorp develops commercially supported security technologies for web applications, servers, endpoints, workloads, and legacy enterprise platforms.

Organizations interested in protecting systems against exploit techniques associated with vulnerabilities such as this one can learn more about:

  • Atomic ModSecurity Rules: commercially maintained WAF rules for ModSecurity deployments, including protections for web attacks, bots, scanners, malware, exploitation attempts, and emerging vulnerability classes.
  • Atomic WAF: an enterprise web application firewall with Atomicorp rules, centralized management, reporting, authentication controls, and operational tooling.
  • Atomic ModSecurity Integrator: a special licensing option for MSPs, MSSPs, OEMs, VARs, reverse proxy providers, and other integrators who want to incorporate Atomicorp ModSecurity rule technology into their own products or services.
  • Atomic OSSEC: an enterprise OSSEC-based intrusion detection, compliance, and security monitoring platform.
  • Atomic Protector: workload protection for Linux, web, cloud, data center, and hybrid environments.

For additional information, product evaluations, or technical discussions, visit https://www.atomicorp.com/ or https://modsecurity.io/ .