CVE-2026-91765
Description
A flaw was found in PHP. An unauthenticated remote attacker could cause a Denial of Service (DoS) by sending a specially crafted request to an affected Simple Object Access Protocol (SOAP) server endpoint. Due to a lack of recursion depth limits when parsing deeply nested XML elements, processing such requests exhausts system stack memory and crashes the application process.
Statement
An important-impact denial-of-service flaw exists in PHP's SOAP extension. When a SoapServer endpoint processes a specially crafted, deeply nested SOAP XML request, unbounded recursion in XML cleanup (and related decode/WSDL helpers) can exhaust the process stack and crash the PHP worker. Exploitation requires a reachable SoapServer that loads ext/soap; typical PHP applications that do not enable the SOAP extension or expose SoapServer are not affected by this attack path. Under PHP-FPM, repeated requests can exhaust the worker pool and take the application offline. Red Hat enterprise hardenings such as ASLR, NX, FORTIFY_SOURCE, and SELinux do not mitigate this stack-exhaustion DoS.
Mitigation
If SoapServer is unused, disable or remove the SOAP extension (php-soap / extension=soap) so the vulnerable parser is not loaded. Restrict any exposed SoapServer endpoints to trusted clients using a host firewall or network segmentation. Process and cgroup resource limits may contain host impact but do not prevent PHP-FPM worker crashes or pool exhaustion from crafted nested SOAP requests.
Common Vulnerability Scoring System (CVSS) Score Details
Info alert:Important note
CVSS scores for open source components depend on vendor-specific factors (e.g. version or build chain). Therefore, Red Hat's score and impact rating can be different from NVD and other vendors. Red Hat remains the authoritative CVE Naming Authority (CNA) source for its products and services (see Red Hat classifications).
CVSS v3 Score Breakdown
| Red Hat | NVD | cve.org | |
|---|---|---|---|
| Base Score | 7.5 | N/A | 7.5 |
| Attack Vector | Network | N/A | Network |
| Attack Complexity | Low | N/A | Low |
| Privileges Required | None | N/A | None |
| User Interaction | None | N/A | None |
| Scope | Unchanged | N/A | Unchanged |
| Confidentiality | None | N/A | None |
| Integrity Impact | None | N/A | None |
| Availability Impact | High | N/A | High |
Vector
Red Hat: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
cve.org: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
Understanding the Weakness (CWE)
Availability
Technical Impact: DoS: Resource Consumption (CPU); DoS: Resource Consumption (Memory)
Resources including CPU, memory, and stack memory could be rapidly consumed or exhausted, eventually leading to an exit or crash.
Confidentiality
Technical Impact: Read Application Data
In some cases, an application's interpreter might kill a process or thread that appears to be consuming too much resources, such as with PHP's memory_limit setting. When the interpreter kills the process/thread, it might report an error containing detailed information such as the application's installation path.
Frequently Asked Questions
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