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Deserialization of Untrusted DataWeakness · CWE-502

CVE-2026-43633

CRITICAL · 10.0 CVSS v3.1 Published 2026-05-19
Patch available
A vendor patch is available. No clean upgrade release — apply the published patch.
See remediation →
100/100
Remediation priority · Urgent
Remotely reachable No privileges Zero-click Patch available

Official description Straight from the sourceThe vendor's or NVD's own wording, published unedited. Authoritative, but often terse — it says what broke, rarely what to do.

NVD · unedited
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.

Technical summary Written by usOur analysis, written from the advisory, the CVSS vector and the affected-version data. It adds context the advisory leaves out, and never invents facts that are not in the source.

dbcve analysis · moderate confidence

HestiaCP versions 1.9.0-1.9.4 have a deserialization vulnerability in the web terminal component caused by a session format mismatch between PHP and Node.js. Attackers can inject crafted data into HTTP headers that PHP processes as session data, which the Node.js web terminal then deserializes as trusted session values, enabling unauthenticated remote code execution with root privileges.

MitigationDisable the web terminal feature immediately until a patched version is available. If the feature must remain enabled, restrict network access to the web terminal endpoints at the network perimeter as a temporary control.

Verify against the referenced sources before acting — the references below are authoritative for this CVE, this summary is not.

CVSS breakdown How the score is builtThe industry scoring standard. It rates how the flaw is reached, what it takes to exploit, and what an attacker gains — the score is derived from those, not the other way round.

From the vector
Attack vector
Network
Complexity
Low
Privileges
None
User interaction
None
Scope
Changed
Confidentiality
High
Integrity
High
Availability
High

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

Am I affected? How to checkSteps we derive from the advisory and the affected-version data, so you can decide whether this CVE reaches your setup. They are a guide, not a scan — your own configuration is the authority.

dbcve checks

Work through these to decide whether this CVE applies to you.

  1. Identify HestiaCP version
    Run 'v-list-sys-info' or check /usr/local/hestia/bin/hestia version file to see the installed HestiaCP version number
    Affected if Version is 1.9.0, 1.9.1, 1.9.2, 1.9.3, or 1.9.4
  2. Verify web terminal is enabled
    Check the HestiaCP control panel settings or examine the web terminal configuration file in /usr/local/hestia/data/templates/web/ for terminal-related configs; look for 'terminal' or 'webshell' in enabled features
    Affected if The web terminal feature is active or installed
  3. Confirm PHP component is in use
    Check if PHP is installed as part of HestiaCP by running 'php -v' or examining installed packages, and verify the web frontend uses PHP handlers
    Affected if PHP is handling web requests for the control panel
  4. Confirm Node.js component is in use
    Check for Node.js installation via 'node -v' or look for Node.js processes related to HestiaCP in running processes; examine if any HestiaCP services use Node.js
    Affected if Node.js is installed and running as part of HestiaCP services
  5. Inspect HTTP header session handling
    Review web server configuration (nginx/apache) for how session cookies and headers are passed between PHP and any Node.js components; check for proxy rules that forward headers to both backend types
    Affected if HTTP headers are forwarded to both PHP and Node.js backends without sanitization

You are affected if running HestiaCP version 1.9.0 through 1.9.4 with the web terminal feature enabled and both PHP and Node.js components handling sessions.

Generated from the published advisory. Verify against your own configuration.

Check your environment

Paste your version and any relevant configuration and it will be compared against the affected criteria above. Do not include secrets or credentials.

AI-assisted, checked against the advisory. Informational, not a guarantee.

Remediation Closing itWhat it takes to close this. Where a vendor fix exists we point at it; where none exists we say so plainly, and can build one. Effort estimates are scoped from the advisory, not from your codebase.

dbcve · scoped
Patch available Apply the vendor patch
Vendor patch github.com →
Interim mitigation

Disable the web terminal feature immediately until a patched version is available. If the feature must remain enabled, restrict network access to the web terminal endpoints at the network perimeter as a temporary control.

Recommended fix Moderate confidence

HestiaCP 1.9.5 or later (latest stable release)

  1. 1. Identify if the HestiaCP web terminal feature is enabled on the system (this feature is required for the vulnerability to be exploitable)
  2. 2. Check the currently installed HestiaCP version using: 'v-list-sys-hestia' or checking the admin panel
  3. 3. If running version 1.9.0 through 1.9.4 and web terminal is enabled, upgrade to the latest HestiaCP release (version 1.9.5 or later which contains the security fix)
  4. 4. After upgrade, verify the new version is installed: 'v-list-sys-hestia'
  5. 5. Review and restart the web terminal service if necessary to ensure the patched components are loaded
  6. 6. Check HestiaCP official release notes for version 1.9.5 or later to confirm the deserialization fix is included
Caveat Minor: Review release notes for any configuration changes between 1.9.x versions; web terminal functionality should remain intact after upgrade

Generated from the published advisory — verify against the referenced sources before acting.

Have this fixed Scoped from the published advisory
  • Consultation4.0 h
  • Implementation12.0 h
  • Testing6.0 h
  • Review / QA3.0 h
25.0 hours of engineering $4,400
Get the patch applied

An estimate, not a bill — we confirm scope with you before any work starts. Need it this week? Rush from $7,040.

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References Go to the primary sourcePrimary sources — vendor advisories, patches and trackers. Where our summary and a reference disagree, the reference wins.

Primary sources

Practitioner notes

Contributed

Peer-ranked notes from engineers who’ve handled CVE-2026-43633 in production — separate from our analysis above.

No notes yet

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What this is

A place for practitioners to share what actually worked: a mitigation you’ve tested, a configuration change, a version- or environment-specific caveat, or a link to a verified patch. The most useful notes rise to the top as peers upvote them, so the signal stays high.

What belongs here
  • Verified mitigations, workarounds, and config changes
  • Version or environment caveats, and links to real fixes
  • No weaponised exploit code, or anything meant to cause harm
  • No spam, self-promotion, credentials, or personal data