CVE-2026-90881

Executive Summary

CVE-2026-90881 is an information disclosure vulnerability affecting the D-Link DIR-882 wireless router (firmware up to 20260814). The flaw resides in the main function of the CGI binary /HNAP1/dllog.cgi, which can be manipulated remotely to leak sensitive information (CWE-200). With a CVSS v3.1 base score of 5.3 (AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:N/A:N), exploitation requires no authentication and no user interaction, and public exploit availability increases the risk of active scanning and abuse.

Technical Analysis

The vulnerability is an instance of CWE-200 (Exposure of Sensitive Information to an Unauthorized Actor). The NVD description identifies the affected component as the CGI binary executed via the path /HNAP1/dllog.cgi, specifically the main function. The HNAP1 (Home Network Administration Protocol) endpoint is a SOAP-over-HTTP management interface commonly exposed on D-Link routers, and /HNAP1/dllog.cgi appears to expose diagnostic logging functionality. Because the flaw is reachable through a remote, unauthenticated request and the CVSS integrity and availability subscores are "None," the impact is confined to confidentiality. The description does not disclose the exact parameter, HTTP method, or input transformation that triggers the disclosure; therefore the precise code-level defect cannot be reconstructed from available data. At the vulnerability-class level, information disclosure in a CGI main handler typically arises when user-supplied input influences which file, log entry, memory region, or environment value is returned to the client without adequate access control or output sanitization. The "manipulation" language indicates that crafted input to the endpoint alters the response content, disclosing data that should not be returned to an unauthenticated remote client. No technical detail beyond the function, file, and component is provided in the NVD entry; any further specifics would be speculative.

Exploitation Scenarios

Because no public PoC code, Nuclei template, or exploit artifact is present in the provided intelligence, the following steps are described at the vulnerability-class level and are inferred from the CWE-200 classification and the remote, unauthenticated CVSS profile.

1. Reconnaissance / Target Identification. An attacker scans internet-facing or LAN-accessible hosts for the D-Link DIR-882 management interface. The /HNAP1/ path and the presence of dllog.cgi are the primary indicators. Shodan-style queries for http.html:"HNAP1" or product:"D-Link DIR-882" can identify candidate devices.

2. Triggering the Flaw. The attacker sends a crafted HTTP request to /HNAP1/dllog.cgi. The "manipulation" referenced in the NVD description implies that a specific input supplied by the attacker causes the main function to return information that is not intended for unauthenticated disclosure. The exact parameter, method (GET vs. POST), and payload structure are not specified in the available intelligence and cannot be stated without fabrication.

3. Payload / Execution (class-level). Since this is an information disclosure issue rather than code execution, the "payload" is a malformed or specially-configured request that coerces the CGI binary into revealing sensitive output. No memory corruption, command injection, or authentication bypass is implied by the CWE-200 classification or the CVSS vector (I:N/A:N).

4. Post-Exploitation Impact. Disclosed information may include device diagnostic data, log contents, configuration fragments, or environment details that aid further attacks (e.g., credential harvesting, network mapping, or chaining into other router flaws). With C:L (Low confidentiality impact), the scope of a single disclosure is limited, but the unaudited, unauthenticated access makes the flaw a useful reconnaissance primitive.

No public PoC is available in the supplied data; the attack chain is inferred strictly from the vulnerability class.

Impact Assessment

• Confidentiality: Low (C:L). Only limited information is exposed per request, but repeated unauthenticated queries can aggregate useful intelligence.
• Integrity: None (I:N). No data modification is indicated.
• Availability: None (A:N). No denial-of-service impact is indicated.
• Scope: Unchanged (S:U). The vulnerable component's authority is not exceeded.
• Attack Vector: Network (AV:N). Exploitable remotely.
• Attack Complexity: Low (AC:L). No special conditions or race windows are required.
• Privileges Required: None (PR:N). No authentication needed.
• User Interaction: None (UI:N). No victim action required.

Blast radius: Primarily D-Link DIR-882 devices with reachable /HNAP1/ management interfaces, particularly those exposed to the internet or to untrusted internal segments. SOHO and small-branch deployments are the most common risk profile. Although the per-incident CVSS impact is moderate, the combination of no authentication, low complexity, and public exploit availability (EPSS 0.00409, ~34.6th percentile) makes this a persistent exposure on unpatched devices.

Detection Guidance

Sigma Rule

title: D-Link DIR-882 dllog.cgi Information Disclosure Attempt
id: 7b1c3e9a-2f6d-4a5e-9c1b-8d0e2f3a4b5c
status: experimental
description: Detects HTTP requests targeting the HNAP1 dllog.cgi endpoint on D-Link DIR-882 devices, associated with CVE-2026-90881.
logsource:
  category: webserver
detection:
  selection_uri:
    cs-uri-stem|contains|all:
      - '/HNAP1/'
      - 'dllog.cgi'
  selection_status:
    sc-status:
      - 200
      - 500
  condition: selection_uri and selection_status
falsepositives:
  - Legitimate administrative diagnostics
  - Vulnerability scanner traffic
level: medium
tags:
  - attack.t1190
  - cve.2026.90881

YARA Rule

rule CVE_2026_90881_DLink_DIR882_dllog_HNAP
{
    meta:
        author = "valtersit.com"
        description = "Detects references to D-Link DIR-882 dllog.cgi HNAP1 endpoint associated with CVE-2026-90881"
        cve = "CVE-2026-90881"
        reference = "https://nvd.nist.gov/vuln/detail/CVE-2026-90881"
        date = "2026-01-01"

    strings:
        $hnap = "/HNAP1/" ascii nocase
        $cgi  = "dllog.cgi" ascii nocase
        $dir  = "DIR-882" ascii nocase

    condition:
        (uint16(0) == 0x4745 or uint32(0) == 0x20544547 or $hnap or $cgi) and
        ($hnap or $cgi) and
        ($dir or $hnap)
}

Suricata IDS Rule

alert http any any -> any any (msg:"CVE-2026-90881 D-Link DIR-882 dllog.cgi Information Disclosure Attempt"; flow:established,to_server; http.uri; content:"/HNAP1/"; http.uri; content:"dllog.cgi"; http.method; content:"GET" or content:"POST"; classtype:attempted-recon; reference:cve,2026-90881; reference:url,nvd.nist.gov/vuln/detail/CVE-2026-90881; sid:202690881; rev:1;)

Elastic Detection

sequence by source.ip with maxspan=30s
  [network where http.request.method in ("GET","POST") and
     url.path : "/HNAP1/*dllog.cgi*"]
  [network where http.response.status_code in (200,500)]

Splunk SPL Query

index=web OR index=network sourcetype=access_combined OR sourcetype=suricata
| search uri_path="*dllog.cgi*" OR http.url="*dllog.cgi*" OR url="*HNAP1*"
| stats count min(_time) as first_seen max(_time) as last_seen by src_ip, uri_path, http.url, status
| where count > 0
| table src_ip, uri_path, http.url, status, count, first_seen, last_seen
| sort - count

Wazuh OSSEC Rule

<group name="web,attack,">
  <rule id="100881" level="10">
    <decoded_as>web-accesslog</decoded_as>
    <url>/HNAP1/.*dllog\.cgi</url>
    <description>CVE-2026-90881: D-Link DIR-882 dllog.cgi HNAP1 information disclosure attempt detected.</description>
    <mitre>
      <id>T1190</id>
    </mitre>
    <group>cve_2026_90881,</group>
    <options>no_full_log</options>
  </rule>
</group>

Mitigation & Patch Guidance

Patch confidence: 0/4 (UNPATCHED — no patch evidence from any tracked source).

1. Immediate mitigations.

   • Restrict access to the /HNAP1/ interface: disable remote management, block WAN-side access to the router's web UI, and bind management to the LAN only.
   • Apply firewall/ACL rules to deny external access to TCP/80 and TCP/443 on the DIR-882.
   • Monitor for requests to /HNAP1/dllog.cgi and treat them as hostile until a patch is available.
   • If the router cannot be isolated, consider segmenting it onto a dedicated VLAN with no access to sensitive internal resources.

2. Patch / upgrade steps.

   • No vendor patch is referenced in any tracked source for this CVE. Monitor D-Link's official security advisory page and firmware download portal for the DIR-882.
   • Until a fix is released, treat the device as untrusted and enforce the network mitigations above.

3. Long-term hardening.

   • Replace end-of-support SOHO routers with devices that receive regular firmware security updates.
   • Disable unused management interfaces (HNAP, UPnP, remote administration) by default.
   • Deploy continuous exposure monitoring (Shodan/Censys) for your external IP ranges and alert on management interfaces appearing publicly.
   • Integrate CVE feeds with asset inventory to ensure routers are inventoried and tracked for patch status.

References

1. NVD — CVE-2026-90881: https://nvd.nist.gov/vuln/detail/CVE-2026-90881
2. CWE-200 — Exposure of Sensitive Information to an Unauthorized Actor: https://cwe.mitre.org/data/definitions/200.html
3. D-Link Security Advisories (vendor advisory portal): https://supportannouncement.us.dlink.com/
4. MITRE ATT&CK T1190 — Exploit Public-Facing Application: https://attack.mitre.org/techniques/T1190/
5. CISA Known Exploited Vulnerabilities Catalog (status check): https://www.cisa.gov/known-exploited-vulnerabilities-catalog

Threat actor / exploit-in-the-wild note: No threat actor attribution or confirmed in-the-wild exploitation campaign is present in the provided data. The NVD description states that an exploit "has been made available to the public and could be used for attacks," and the PoC status is recorded as Public. EPSS is 0.00409 (~34.6th percentile), indicating a historically low but non-zero likelihood of observed exploitation in the wild. This CVE is not listed in CISA KEV.