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CVE Record

CVE-2026-43634: HestiaCP 1.2.0-1.9.4 IP Spoofing via CF-Connecting-IP Header

HestiaCP versions 1.2.0 through 1.9.4 contain an IP spoofing vulnerability that allows unauthenticated remote attackers to bypass authentication security controls by supplying an arbitrary IP address in the CF-Connecting-IP HTTP header without verifying the request originated from Cloudflare's network. Attackers can exploit this to circumvent fail2ban brute-force protection, bypass per-user IP allowlists, and poison authentication audit logs by spoofing trusted IP addresses on each request.

HighCVSS 8.7Not KEV-listedUpdated
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Glexia's TakeAutomated analysishigh

Security readout for executives and security teams

Plain-English summary

HestiaCP trusted a Cloudflare client-IP header without confirming the request actually came through Cloudflare. An internet attacker could make login-related requests appear to come from chosen IP addresses, weakening brute-force blocking, IP allowlists, and audit trails.

Executive priority

Treat as high priority for internet-facing control panels. The issue may not directly grant code execution, but it can undermine login defenses and audit reliability during attacks.

Technical view

CVE-2026-43634 affects HestiaCP 1.2.0 through 1.9.4. The application accepts arbitrary CF-Connecting-IP values without validating Cloudflare source networks, enabling unauthenticated remote IP spoofing against authentication security controls. Sources cite CWE-348 and CVSS 4.0 score 8.7.

Likely exposure

Exposed HestiaCP admin interfaces are most at risk, especially where fail2ban, per-user IP allowlists, or authentication investigations rely on logged client IPs.

Exploitation context

The source bundle includes technical/exploit-labeled references, but KEV is false and no provided source confirms active exploitation in the wild.

Researcher notes

Evidence supports unauthenticated network exploitation for IP spoofing, not confirmed real-world exploitation. The provided bundle references a patch commit, GitHub issue, PR, CVE record, and third-party advisory; fixed release details should be confirmed from HestiaCP guidance.

Mitigation direction

  • Review HestiaCP vendor issue, PR, and patch guidance immediately.
  • Upgrade or patch to code that fixes CF-Connecting-IP trust handling.
  • Restrict HestiaCP admin access to trusted networks or VPNs.
  • Trust proxy client-IP headers only from verified Cloudflare source networks.
  • Review authentication controls that depend on client IP address.

Validation and detection

  • Inventory HestiaCP versions and flag 1.2.0 through 1.9.4.
  • Confirm patched code validates Cloudflare origin before using CF-Connecting-IP.
  • Review logs for CF-Connecting-IP use from non-Cloudflare sources.
  • Check authentication logs for inconsistent or suspicious client IP patterns.
  • Verify fail2ban and allowlist decisions use trustworthy client IP data.
Prepared
Confidence
high
Sources
7

Public sources used

Generated from the cited source records. This long-tail analysis has not been individually reviewed by a named human.

Potential ATT&CK relevance

Conservative CVE-to-ATT&CK context

These mappings and lookup hints may be relevant to the vulnerability behavior, CWE, affected product, or exposure path. Glexia-inferred context is not an official MITRE, ATT&CK, CWE, or CVE Program mapping.

ATT&CK lookup starting points

Use these exact CWE pages and searches to review the Glexia ATT&CK library from this CVE's weakness and description context.

cwe · low confidence lookup

CWE-348: Exact CWE lookup

Use the exact CWE identifier as the starting point before reviewing related ATT&CK behavior. Open the exact CWE lookup page first, then review the ATT&CK searches from that MITRE weakness context. This is a Glexia lookup hint, not an official ATT&CK mapping.

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cve · low confidence lookup

CVE-2026-43634 mapping review

Open the CVE-to-ATT&CK bridge for reviewed, inferred, or future official mappings tied to this CVE.

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Vulnerability profileCVE Program record
Severity
High
CVSS
8.7 (4.0)
Known Exploited
No
Published

Vector: CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:H/VA:N/SC:N/SI:N/SA:N

Official CVE source material

CNA and ADP enrichment extracted from CVE v5

These fields come from the CVE record and ADP containers, not from Glexia's Take. They preserve time-varying source decisions such as CISA SSVC, KEV status, CVSS metrics, and provider references.

2CVSS vectors
3Timeline events
1ADP providers
6Source links

SSVC decision data

CISA-ADPCISA Coordinator
Timestamp
Version
2.0.3
Exploitation: pocAutomatable: yesTechnical Impact: partial

CVSS vector scores

2 official scores

We collect every scored CVSS vector available in the official CNA and ADP containers. When more than one version is present, the table keeps the source vectors side by side instead of collapsing them into the highest score.

ScoreVersionSeverityVectorExploitImpactSource
8.7CVSS 4.0HighCVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:H/VA:N/SC:N/SI:N/SA:N——VulnCheck
7.5CVSS 3.1HighCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N3.93.6VulnCheck

Vulnerability scoring details

Base CVSS 4.0 score

8.7High
CVSS 4.0 vector shape for CVE-2026-43634Attack VectorAttack ComplexityAttack RequirementsPrivileges RequiredUser InteractionVS ConfidentialityVS IntegrityVS AvailabilitySS ConfidentialitySS IntegritySS Availability

Vector: CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:H/VA:N/SC:N/SI:N/SA:N

Attack Vector
NetworkAdjacentLocalPhysical
Attack Complexity
LowHigh
Attack Requirements
NonePresent
Privileges Required
NoneLowHigh
User Interaction
NonePassiveActive
VS Confidentiality
HighLowNone
VS Integrity
HighLowNone
VS Availability
HighLowNone
SS Confidentiality
HighLowNone
SS Integrity
HighLowNone
SS Availability
HighLowNone

Vulnerability timeline

Timeline events are normalized from CVE metadata, CNA source timelines, ADP timelines, and KEV metadata when present.

  1. CVE reservedCVE Program

    The CVE ID was reserved by the assigning CNA.

  2. CVE publishedCVE Program

    The CVE record was published.

  3. CVE updatedCVE Program

    The CVE record metadata indicates this as the latest update time.

ADP provider summaries

CISA-ADPCISA ADP Vulnrichment
other:ssvc

Source materials

Affected products

Products and packages named in the record

VendorProductVersion / packageStatus
hestiacphestiacp1.2.0, f381e294500f671cf12716c638afd0bfde901f88affected
Weakness

CWE details

CWE-348

CWE links open Glexia weakness intelligence pages with official CWE context, developer remediation guidance, and related CVE mappings.

CWE-348 · source CWE mapping

Use of Less Trusted Source

Use of Less Trusted Source represents a recurring weakness pattern that can create exploitable paths when design, validation, or implementation controls are missing.

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