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HTMLy CVE-2026-18646

| EUVDEUVD-2026-52431 MEDIUM
Path Traversal (CWE-22)
2026-08-03 VulDB GHSA-pq92-gfff-99hc
5.5
CVSS 4.0 · Vendor: VulDB
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Attack ChainAIDerived

Hypothetical attack flow derived from CVE metadata – not a confirmed exploit chain

  1. Access
    Send HTTP request to /system/htmly.php
  2. Delivery
    Inject traversal sequences in Name parameter
  3. Exploit
    Escape intended web root directory
  4. Execution
    Read arbitrary files accessible to web process
  5. Impact
    Exfiltrate credentials or sensitive configuration data

Vulnerability Assessment

Weakness
CWE
OWASP Top 10:2025
A01:2025 - Broken Access Control
ASVS 5.0
V5 - File Handling Path canonicalization, traversal prevention
MITRE ATT&CK

2 techniques across 2 tactics: Discovery, Collection

The technique list with ATT&CK links and the kill-chain view is part of the Basic plan and up.

Exploitation Conditions

No special conditions are required for exploitation - the CVSS 4.0 vector confirms network-accessible (AV:N), low-complexity (AC:L), no-attack-requirements (AT:N), unauthenticated (PR:N), no-user-interaction (UI:N) exploitation against default HTMLy deployments up to version 3.1.1. Any instance of HTMLy with /system/htmly.php reachable over HTTP or HTTPS is a viable target. Exploitation is limited to file read operations (VC:L) on the vulnerable system; the attacker can only read files accessible to the web server process user, so the extent of disclosure depends on filesystem permissions and what sensitive data resides on the host. No write or code execution capability is indicated by this vector.

Impact

The CVSS 4.0 base vector (AV:N/AC:L/AT:N/PR:N/UI:N) presents a worst-case accessibility profile - unauthenticated, low-complexity, network-reachable with no attack requirements - making any internet-exposed HTMLy instance a trivially reachable target. However, impact is bounded: VC:L with VI:N/VA:N/SC:N/SI:N/SA:N indicates file read capability only, with no integrity, availability, or cross-system impact confirmed. This is meaningfully less severe than code execution. The E:P supplemental metric confirms a public POC exists, which elevates practical risk beyond the base score alone. No EPSS score or CISA KEV listing is present in the source data - exploitation is not confirmed as active, only possible. The vendor's non-response to disclosure removes the possibility of coordinated remediation, leaving users without official guidance. Real-world risk is moderate for exposed instances: file reads can expose credentials, configuration secrets, or private content stored on the server, even without full compromise.

Exploit ScenarioDerived

An unauthenticated remote attacker sends a crafted HTTP request to a publicly exposed HTMLy instance at /system/htmly.php, injecting path traversal sequences (e.g., ../../etc/passwd or ../../config.yaml) into the Name parameter. The server resolves the path outside the web root and returns the contents of sensitive files - potentially including application credentials, API keys, or system user data - readable by the web server process. A public POC at https://github.com/orionyan520/cve_report/issues/7 means this attack is replicable without technical sophistication.

This Month Plan within 30 days. Why: MEDIUM severity (CVSS 4.0-6.9).
No patch listed yet 0.5% exploitation probability (EPSS)

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AnalysisAIv1 – Aug 03, 2026

Path traversal in danpros HTMLy up to version 3.1.1 allows remote unauthenticated attackers to read arbitrary files from the server filesystem by manipulating the Author Name argument in /system/htmly.php. A publicly available proof-of-concept exploit (E:P per CVSS 4.0 supplemental metric) exists at a referenced GitHub issue, materially lowering the exploitation bar. The vendor was unresponsive to responsible disclosure, leaving no vendor-confirmed patch and no official mitigation guidance.

RemediationAI

No vendor-released patch has been identified at time of analysis - the vendor did not respond to responsible disclosure. Administrators running HTMLy 3.1.1 or earlier should restrict public HTTP access to the /system/ directory path via web server rules (e.g., nginx deny or Apache Require all denied for /system/), noting this may impair administrative functionality and should be tested before deployment. Input validation or WAF rules blocking traversal sequences (../, ..\) in query parameters provide a detection and partial blocking layer, though WAF bypass is possible. File system permissions should be reviewed to ensure the web server process cannot read sensitive files outside the web root (e.g., /etc/passwd, application secrets). Given vendor non-responsiveness, migration to an actively maintained flat-file or database-backed CMS is the most durable long-term remediation. Monitor VulDB entry https://vuldb.com/vuln/385565 for any future patch release.

Affected VersionsENISA

htmly 3.1.0
htmly 3.1.1

Affected Packages

euvd htmly no fix

Source: OSV (Open Source Vulnerabilities)

Affects your stack

Affects 1 package in euvd

Checking this CVE against your own stacks and servers is part of the Basic plan and up.

Technical ContextAI · show details

HTMLy is a flat-file blog CMS written in PHP that stores content in flat YAML/Markdown files rather than a relational database. The vulnerability resides in the Author Name Handler within /system/htmly.php, where user-supplied input to the Name argument is insufficiently sanitized before being used in a filesystem operation. This permits directory traversal sequences (e.g., ../../) to escape the intended file root, enabling reads of arbitrary files accessible to the web server process. CWE-22 (Improper Limitation of a Pathname to a Restricted Directory) identifies the root cause class: the application fails to canonicalize or validate path components before use. The affected CPE is cpe:2.3:a:danpros:htmly:*:*:*:*:*:*:*:*, covering all HTMLy releases through 3.1.1.

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  • Exploit and PoC references, threat intelligence from 22 sources

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Severity by source

Vendor (VulDB) PRIMARY 5.5 MEDIUM
CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:L/VI:N/VA:N/SC:N/SI:N/SA:N/E:P
vuln.today AI 5.3 MEDIUM

Network-reachable unauthenticated path traversal with read-only low-confidentiality impact; no integrity, availability, or scope-change consequence applies.

3.1 AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:N/A:N
4.0 AV:N/AC:L/AT:N/PR:N/UI:N/VC:L/VI:N/VA:N/SC:N/SI:N/SA:N

Primary rating from Vendor (VulDB).

CVSS VectorVendor: VulDB

Attack Vector
Network
Attack Complexity
Low
Attack Requirements
None
Privileges Required
None
User Interaction
None
Vulnerable system: Confidentiality
Low
Vulnerable system: Integrity
None
Vulnerable system: Availability
None
Subsequent system: Confidentiality
None
Subsequent system: Integrity
None
Subsequent system: Availability
None

Lifecycle Timeline

2
CVSS changed
Aug 03, 2026 - 21:22 NVD
6.9 (MEDIUM) 5.5 (MEDIUM)
CVE Published
Aug 03, 2026 - 20:30 cve.org
MEDIUM 6.9

DescriptionCVE.org

A weakness has been identified in danpros HTMLy up to 3.1.1. This vulnerability affects unknown code of the file /system/htmly.php of the component Author Name Handler. Executing a manipulation of the argument Name can lead to path traversal. The attack may be launched remotely. The exploit has been made available to the public and could be used for attacks. The vendor was contacted early about this disclosure but did not respond in any way.

Threat Intelligence Overview

EPSS Score
0.5%
Top 58% exploitable
Prevalence
Rare
niche flat-file PHP CMS with limited enterprise adoption
Exploit
POC
Public exploit code exists
Data Quality
7 sources
Confidence: High
EUVD NVD CVE.org EPSS Vulnrichment GitHub VulDB

How this decision was reached

The engine reads each signal below and applies a fixed list of rules from top to bottom. The first rule that matches sets the recommended action – like a statement, every line is shown.

SignalValue
Severity MEDIUM
CISA KEV No
Public POC Yes
EPSS 0.5%
Patch available No
Active threat No
Deciding rule
MEDIUM severity (CVSS 4.0-6.9)
What every action level means
Emergency Immediate action required. Criteria: CRITICAL + in CISA KEV (actively exploited) without patch, OR CRITICAL + EPSS > 30% without patch, OR CRITICAL + active threat signals without patch.
Act Now Prioritize within 24-48h. Criteria: in KEV with patch available, OR CRITICAL + public POC, OR HIGH + EPSS > 10%, OR CRITICAL + active threat, OR any CRITICAL severity.
This Week Schedule remediation this week. Criteria: HIGH severity (CVSS 7.0-8.9). Patch within normal change window.
This Month Plan within 30 days. Criteria: MEDIUM severity (CVSS 4.0-6.9), lower exploitation probability. Include in regular patch cycle.
Monitor Track and reassess. Criteria: LOW severity (CVSS 0.1-3.9), minimal exploitation risk. No immediate action needed.

SSVC AssessmentENISA

SSVC Decision· derived
Scheduled
Exploitation
Poc
System Exposure· derived
Open
Automatable
Yes
Human Impact· derived
Medium
Technical Impact
Partial

Priority Score

49
Low Medium High Critical
KEV: 0
EPSS: +1
CVSS: +28
PoC: +20
Weaponized: 0
Threat intel: 0
Gov advisory: 0

Attack Technique

Path traversal exploits occur when applications use user-controlled input to construct file system paths without proper validation.

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