CVSS 10.0CVSS 10.0 · CRITICAL

CVE-2026-43633

HestiaCP versions 1.9.0 through 1.9.4 contain a deserialization vulnerability in the web terminal component caused by a session format mismatch between PHP and Node.js that allows unauthenticated remote attackers to achieve root-level code execution. Attackers can inject crafted data into HTTP headers that are processed by the PHP session handler but incorrectly deserialized by the Node.js web terminal component as trusted session values, resulting in arbitrary command execution on systems with the web terminal feature enabled.

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Analysis

A critical unauthenticated RCE vulnerability has been identified in HestiaCP versions 1.9.0 through 1.9.4. Attackers can achieve root access by exploiting a session deserialization mismatch between PHP and Node.js via crafted HTTP headers. Systems with the web terminal feature enabled should be updated immediately.

Relevant roles

PhpLinuxCyberSecurityBackendJavascript

Severity

Score: 10.0(CRITICAL)

Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:H/I:H/A:H

AV: NETWORK

AC: LOW

PR: NONE

UI: NONE

S: CHANGED

C: HIGH

I: HIGH

A: HIGH

Weakness (CWE): CWE-502

EPSS

Probability of exploitation (next 30 days): 0.0020 (0.2%)

Percentile: 42.1%

EPSS: 2026-05-25

Technical description

Published: 5/19/2026, 2:16:43 PM

Last modified: 5/19/2026, 2:43:04 PM

References

How to read this card

Actively exploited

KEV (Known Exploited Vulnerabilities) is CISA's catalog of CVEs confirmed as actively exploited in the real world. If a CVE is on KEV, someone is already using it in attacks.

CVSS 10.0

CVSS 10.0 — máxima severidad teórica. Explotable de forma remota, sin privilegios, con impacto total. Aún no confirmada como explotada en el mundo real, pero parchea ya.

AI-recommended

Un modelo de lenguaje revisó el CVE y consideró que afecta a software ampliamente desplegado o herramientas comunes de desarrollo. Un humano del equipo aprobó la publicación antes de que llegara aquí.

Categorías de impacto que evalúa la IA

widely_deployed_infra — kernel Linux, OpenSSL, glibc, k8s, Docker, nginx, OpenSSH.

popular_dev_tooling — Node.js, Python, Go, React, Next.js, librerías comunes de npm/pip.

common_consumer_software — Chrome, Firefox, Windows, macOS, apps móviles populares.

enterprise_saas — GitHub, GitLab, Atlassian, Salesforce, Cisco, Fortinet, Ivanti.

niche_software — CMS regionales, herramientas de hobby, librerías de poco uso.

not_relevant — firmware específico de proveedor, software descontinuado.

EPSS — EPSS (Exploit Prediction Scoring System) by FIRST.org estimates the probability that a CVE will be exploited in the next 30 days. Range is 0 to 1; very fresh CVEs typically score low until evidence accumulates.