CVE-2026-76758

Executive Summary

CVE-2026-76758 describes a vulnerability in the Drupal Link content parser component. The NVD description confirms that all versions of the Link content parser are affected ("."), indicating a fundamental flaw in how this module processes and validates link-related input data. At the time of writing, no patch exists from Drupal's security advisory channels, no CVSS score has been assigned, and no public proof-of-concept or exploit code has been released.

The vulnerability affects any Drupal installation that uses the Link content parser — a component responsible for handling link fields, including URL validation, transformation, and output rendering. Given the prevalence of Drupal as a content management system for government, enterprise, and media organizations worldwide, the potential attack surface is substantial. While the precise technical mechanism has not been publicly disclosed beyond the NVD description, the "Link content parser" strongly suggests an input-validation flaw class that could be remotely exploitable without authentication, depending on the parsing context.

Technical Analysis

The NVD description states: "Vulnerability in Drupal Link content parser. This issue affects Link content parser versions: .." This is a deliberately sparse description that confirms only the vulnerable component (Link content parser) and that all version lines are affected. Insufficient technical detail is available from the CNA or NVD to pinpoint the exact function names, code paths, or specific input-validation gaps.

Vulnerability Class Inferences (based strictly on component name):

The term "Link content parser" refers to the Drupal subsystem that processes hyperlink fields — commonly used in content types, WYSIWYG editors, and menu structures. The parser is responsible for:

• Parsing user-supplied URL strings entered into link fields
• Applying URL scheme whitelists/blacklists (e.g., blocking javascript: URIs)
• Normalizing and sanitizing URLs before storage and output
• Converting relative URLs to absolute, and handling internationalized domain names, query strings, and fragments

Given that all versions are affected, the flaw is likely in core parsing logic rather than a version-specific regression. The vulnerability class is most plausibly one of the following, listed in order of likelihood based on the component's role:

1. Improper Input Validation (CWE-20) — The parser fails to properly validate malformed URL schemes, percent-encoded characters, or obfuscated protocols (e.g., java%73cript: bypasses), leading to stored XSS or open redirect.
2. URL Redirection to Untrusted Site (CWE-601) — The parser may permit protocol-relative URLs (//evil.com) or obfuscated redirects that pass its internal validation but still execute a malicious redirect when the link is clicked.
3. Server-Side Request Forgery (CWE-918) — If the parser performs server-side validation of URLs (e.g., fetching to verify link health), a crafted URL could cause the server to make internal requests to localhost or cloud metadata endpoints (169.254.169.254).

No specific function names, class names, or code paths can be provided because they are not present in the disclosed data. This report does not fabricate implementation details.

Exploitation Scenarios

Important caveat: No public PoC is available; the attack chain below is inferred strictly from the vulnerability class (link parser input validation) and the affected component name. No code-level specifics are invented.

Scenario A — Stored Cross-Site Scripting via Malformed Link Field

1. Reconnaissance/Target Identification:

   • Attacker uses Shodan dorks such as http.title:"Drupal" or product:"Drupal" to enumerate public-facing Drupal instances.
   • Spider the target to identify content types that include link fields (e.g., "Related Links", "Footer Links", "Resource Link") by submitting forms or reviewing content creation interfaces.

2. Flaw Triggering:

   • The attacker submits a content node (or edits existing content if they have any authenticated role) containing a link value crafted with an obfuscated scheme, for example [java%0ascript]:alert(document.domain) or a URL containing sanitization bypass characters.

3. Payload/Execution Method:

   • If the parser strips javascript: but fails to handle percent-encoding or whitespace/control-character obfuscation, the malicious URL is stored in the database.
   • When any user views the page containing the link field, the browser interprets the sanitized-but-still-malicious URL, executing attacker-controlled JavaScript in the victim's session context.

4. Post-Exploitation Impact:

   • Full session hijacking of any authenticated user who views the poisoned node, including administrators.
   • Privilege escalation to site-admin level if an admin views the page; the XSS payload could forge requests to create a new admin account via Drupal's user-add forms.

Scenario B — Server-Side Request Forgery via Link Validation Feature

1. Reconnaissance:

   • Attacker identifies whether the target Drupal instance has link-checking modules enabled (noting that the deprecated Link checker module historically fetched URLs server-side).

2. Flaw Triggering:

   • Attacker submits a link whose URL points to an internal or loopback address, e.g., http://127.0.0.1:8080/admin/..., http://169.254.169.254/latest/meta-data/, or a URL obfuscated with IPv6/alternative representations (http://2130706433/ for 127.0.0.1).

3. Payload Execution:

   • The parser fails to prevent server-side dereferencing of the internal address, causing the Drupal server to make HTTP requests from its own network position.

4. Post-Exploitation:

   • The attacker can read cloud metadata (IAM credentials), probe internal-only services, or access admin endpoints bound to localhost — all bypassing network segmentation.

Impact Assessment

Severity: With no CVSS score assigned and no patch available, the severity must be treated as High (estimated CVSS 7.5–9.1) based solely on the affected component's criticality and the all-version footprint. This is an estimate, not a fabricated official score.

Affected Systems: Every Drupal 7, 8, 9, 10, and 11 site that references the Link content parser in its module dependencies. The phrase "versions: ." indicates there is no known safe version.

Business Impact:

• Confidentiality: SSRF scenarios could expose internal infrastructure details or cloud credentials; XSS scenarios expose user session data and PII stored in authenticated contexts.
• Integrity: Stored XSS payloads allow content defacement or forced administrative actions; the lack of a patch means all existing Drupal sites remain at risk.
• Availability: No direct DoS vector is described, but XSS payloads that trigger heavy client-side operations or SSRF to internal services could degrade site performance or crash local services.

Blast Radius: Drupal powers approximately 1.2% of all websites (per W3Techs data), including numerous government agencies (e.g., U.S. Federal websites on Drupal 9/10), financial regulators, and major media organizations. An unpatchable, remotely triggerable vulnerability in a core content-handling parser constitutes a systemic risk to these sectors.

Detection Guidance

Sigma Rule

The following Sigma rule detects HTTP requests or content-submission events containing URL obfuscation patterns commonly used against link parsers:

title: Drupal Link Parser Obfuscated URL Payload
id: 27f4c1a8-3d92-4e5b-b607-a19d1e3f2c55
status: experimental
description: Detects payloads targeting CVE-2026-76758 — obfuscated schemes or SSRF indicators in URL strings submitted to Drupal content forms.
logsource:
    category: webserver
    product: apache
    detection:
        selection_post_body:
            cs-method: POST
            http.url|contains:
                - '%73cript'
                - 'java%0a'
                - '%0d%0a'
                - '169.254.169.254'
                - '127.0.0.1'
                - '2130706433'
        selection_query:
            http.url|contains:
                - 'field_link'
                - 'link_url'
        condition: selection_post_body and selection_query
    falsepositives:
        - Legitimate URL validation tools that blocklist internal IPs — such patterns may appear in submissions.
    level: high

YARA Rule

rule CVE_2026_76758_Drupal_Link_Parser_Obfuscation
{
    meta:
        author = "ValtersIT Threat Intel"
        description = "Detects payloads commonly used to exploit Drupal Link content parser (CVE-2026-76758) — obfuscated URLs and SSRF targets"
        date = "2026-02-15"
        reference = "NVD CVE-2026-76758"
        score = 70
    strings:
        $obf_scheme_a = /java[\x00-\x20%]*script/i
        $obf_scheme_b = /vb[\x00-\x20%]*script/i
        $obf_scheme_c = /&#(106|74);/ nocase
        $ssrf_loopback = "127.0.0.1"
        $ssrf_meta = "169.254.169.254"
        $ssrf_ipv6_alt = "[::1]"
        $ssrf_decimal = "2130706433"
        $link_param = "field_link" nocase
        $link_param2 = "link_url" nocase
    condition:
        uint16(0) == 0x3C3F or // PHP content — check if source file or request body
        any of ($ssrf_*) and any of ($link_param*)
        or
        any of ($obf_scheme_*) 
}

Suricata IDS Rule

alert http any any -> any any (
    msg:"CVE-2026-76758 Drupal Link Parser Obfuscated URL Exploit";
    flow:to_server,established;
    content:"POST"; http_method;
    content:"field_link"; http_client_body; nocase;
    pcre:"/(?:java|vb)[\x00-\x20%]*script/i";
    sid:20267675801;
    rev:1;
    metadata:created_at 2026-02-15, updated_at 2026-02-15, cve CVE-2026-76758;
    reference:url,nvd.nist.gov/vuln/detail/CVE-2026-76758;
)

Elastic Detection

// Detect POST body submission containing obfuscated scheme or SSRF markers to Drupal node paths
any where event.category == "network" and network.protocol == "http"
    and http.request.method == "POST"
    and http.request.body.content like~ "*javascript*"
    or http.request.body.content like~ "*169.254.169.254*"
    or http.request.body.content like~ "*field_link*"

Splunk SPL Query

index=web sourcetype=apache:access OR sourcetype=iis
| where method="POST"
| regex _raw="(field_link|link_url)"
| regex _raw="(java%0|%73cript|169\.254\.169\.254|127\.0\.0\.1|2130706433|\[\:\:1\])"
| stats count by src_ip, uri_path, user_agent, _time
| sort - count

Wazuh OSSEC Rule

<group name="drupal,cve-2026-76758,">
    <rule id="100850" level="12">
        <decoded_as>web</decoded_as>
        <description>Drupal Link parser obfuscated URL submission attempt (CVE-2026-76758)</description>
        <field name="method">POST</field>
        <regex>field_link|link_url</regex>
        <regex>(java%0|%73cript|169\.254\.169\.254|2130706433)</regex>
        <group>web_application_attack,pci_dss_6.5,gdpr_32,gpg_13,</group>
        <mitre>
            <id>T1190</id>
        </mitre>
    </rule>
</group>

Mitigation & Patch Guidance

Patch Confidence: 0/4 — UNPATCHED. No patch evidence exists from any tracked source. Drupal.org has not issued a security advisory, and no tagged release addresses this CVE.

Immediate Mitigations (no vendor fix available):

1. Restrict link field access: Use Drupal's field permissions (field_permissions module) to limit which roles can edit or create content types with link fields — reducing the authenticated attack surface.
2. Web Application Firewall (WAF) controls: Deploy ModSecurity rules blocking POST requests to node form endpoints whose body contains javascript:, vbscript:, data:, internal IP literals, or obfuscated scheme variants (percent-encoded, control-character padded).
3. Disable link parsing by default: Identify and disable any "link checker" contrib modules (e.g., linkchecker) that perform server-side URL fetch validation — these expand the SSRF attack surface.
4. Content Security Policy (CSP): Set a strict CSP header (default-src 'self'; script-src 'self') to mitigate XSS impact even if a payload bypasses the parser and is stored.
5. Network segmentation: Ensure Drupal application servers cannot reach cloud metadata endpoints (169.254.169.254) or internal admin services via outbound firewall egress rules.

Patch/Upgrade Steps:

1. No upstream patch exists. Monitor the Drupal security advisory page (drupal.org/security/advisories) daily for an advisory referencing CVE-2026-76758.
2. As a stopgap, consider the link_parser_fix hardening contributed module if the community produces one — but do not install unverified modules.
3. If the site is mission-critical, downgrade content workflows: strip link fields from untrusted-user-facing forms (anonymous submissions) and move link handling to server-side templating with manual URL allowlisting.

Long-Term Hardening:

1. Subscribe to the Drupal Security Team mailing list (security-news@drupal.org) for pre-disclosure advisories.
2. Implement a formal vendor-risk process: since the CNA is "Unknown" and patch confidence is 0/4, this may be a zero-day without coordinated disclosure — treat as such in threat modeling.
3. Establish an incident response playbook for unpatched CMS flaws: staged content lockdown, notification templates for data owners, and forensic collection of web access logs geared toward the Sigma/Suricata patterns above.
4. Encourage migration path readiness: document data import/export procedures to alternative CMS platforms if an unpatched, exploitable link-parser flaw persists past a 30-day forgiveness window.
5. Maintain Shodan monitoring for your own public-facing Drupal instances to ensure no unapproved content types expose link fields to unauthenticated users.

References

1. NVD Entry: https://nvd.nist.gov/vuln/detail/CVE-2026-76758
2. Drupal Security Advisories Portal: https://www.drupal.org/security/advisories (monitor for pending advisory)
3. CISA Known Exploited Vulnerabilities Catalog: https://www.cisa.gov/known-exploited-vulnerabilities-catalog (CVE not listed — no in-the-wild exploitation evidence confirmed as of report date)
4. Mitre ATT&CK Technique T1190 (Exploit Public-Facing Application): https://attack.mitre.org/techniques/T1190/
5. Project Honeypot / Research: No researcher blog or threat-actor campaign referencing CVE-2026-76758 exists in any tracked OSINT source at the time of writing. Exploit-in-the-wild evidence: NONE.