CVE-2026-43633 — HestiaCP 1.9.0-1.9.4 Deserialization RCE via Web Terminal
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.
Who exploits it and how urgent it is
A 0–100 score combining confirmed exploitation, ransomware and APT use, public exploits, EPSS and severity.
How the score was calculated
- EPSS 1.5% (30-day exploitation probability)+11
- Technical severity (critical)+10
- CISA SSVC: exploitation "poc"+5
- Automatable exploitation (SSVC)+3
The score orders the patch queue; it does not replace your asset context (internet exposure, criticality, compensating controls).
Triage
Is it exploited, how likely is exploitation, what does it touch, and how severe do the sources call it.
CISA SSVC assessment CISA
Three decision points CISA publishes for the CVEs it assesses (SSVC 2.0.3). A stakeholder decision, not a severity score.
Remediation
Fixes and mitigations documented by the sources — linked to the original advisory.
No fix documented by the sources we poll. That does not mean none exists: check the vendor advisory.
First 24 hours
Ordered from the record’s own fields — exposure first, because you cannot patch what you have not found. A rule-generated starting point.
- Identify exposed assets running the affected vendor/product/version combinations (Hestiacp Hestiacp).
- The attack is network-based and needs no privileges: restrict exposure (ACLs, VPN, WAF) until patched.
- No fix documented in the sources: reduce exposure and monitor the vendor advisory.
- Search available logs for exploit probes matching the vulnerability class (insecure deserialization), errors and authentication anomalies.
Affected scope
Vendor, product and versions as the sources word them.
Attack characteristics
The CVSS vector, decoded. It describes the attack, not your exposure to it.
Every base score collected
Sources score independently and may disagree; each row says who scored it and under which version.
| Score | Version | Severity | Expl. | Impact | Scored by |
|---|---|---|---|---|---|
| 9.5 | CVSS 4.0 | Critical | — | — | disclosure@vulncheck.com via NIST National Vulnerability Database |
| 9.5 | CVSS 4.0 | Critical | — | — | VulnCheck via CVE Program (cve.org) e CISA ADP |
| 10.0 | CVSS 3.1 | Critical | 3.9 | 6.0 | disclosure@vulncheck.com via NIST National Vulnerability Database |
| 10.0 | CVSS 3.1 | Critical | — | — | VulnCheck via CVE Program (cve.org) e CISA ADP |
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:H/I:H/A:H (score shown at the top: disclosure@vulncheck.com) Weakness MITRE
Weakness class according to MITRE’s CWE catalog.
EPSS over time FIRST
Oct 13, 2026 → Oct 15, 2026 · 3 reading(s) · max 1.49%
Detection
Read off the CVSS vector and the weakness class. Starting points, not tested rules.
- Prioritize edge telemetry for the network-reachable component (proxy, WAF, IDS/IPS).
- Monitor serialized objects in requests and unexpected processes spawned by the runtime.
Timeline
What happened to this CVE, newest first.
- 2026
- Affected products added · hestiacp/hestiacp
- SSVC assessment updated
- Record published
- CVSS changed · 10.0
- Source status changed · → Deferred
- Record created in this database
- CVE published
Source activity
Repeated readings are counted rather than listed.
- 1× Official description updated · Oct 13, 2026 – Oct 13, 2026
References
5 on the record
- github.com/hestiacp/hestiacp/commit/854d71b3c1737b0a0d0cc55c926008ffe1f6719b
- www.vulncheck.com/advisories/hestiacp-deserialization-rce-via-web-terminal
- github.com/hestiacp/hestiacp/pull/5244
- github.com/hestiacp/hestiacp/issues/5229
- mercuryiss.com.au/hestiacp-unauthenticated-rce-ip-spoofing-cve-2026-43633-cve-2026-4363
Elsewhere on this site
Related CVEs (same products)
- Critical CVE-2026-108390 HestiaCP Low-Privileged User to Root via Config-Field Injection and PATH Hijacking 1d
- Medium CVE-2025-30008 HestiaCP < 1.9.5 Stored XSS via DNS Record Management Interface Jul 10, 2026
- High CVE-2025-30007 HestiaCP < 1.9.5 Authenticated OS Command Injection via DNS Record Management Jul 10, 2026
- High CVE-2026-12196 HestiaCP Admin Takeover Jul 4, 2026
- High CVE-2026-43634 HestiaCP 1.2.0-1.9.4 IP Spoofing via CF-Connecting-IP Header May 19, 2026
Not in any source we poll
Listed rather than left blank: an empty field and an unmeasured one look identical on screen, and only one is a reason to look elsewhere.
- No fixed version, patch or mitigation documented.
- No confirmed IOCs, IP addresses, domains, file hashes, or malware artifacts supplied.
- No organization-specific asset inventory, compensating-control status, or patch deployment evidence supplied.
- No exploit packet captures, log samples, or incident case IDs supplied.
Answered from this record
Text assembled only from the fields above — no additional claims.
What should defenders know first?
CVE-2026-43633 is "HestiaCP 1.9.0-1.9.4 Deserialization RCE via Web Terminal", rated Critical. It affects Hestiacp (Hestiacp); versions are in the scope table. It is not in CISA KEV, which does not rule out exploitation. CVSS 10.0 describes technical severity. EPSS 1.49% estimates the probability of exploitation in 30 days; neither replaces your asset context. First verify whether exposed or business-critical assets run the affected versions, apply vendor fixes or mitigations, and preserve logs for review.
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