CVE-2026-64630

Executive Summary

CVE-2026-64630 is an authorization bypass vulnerability in the HackerOne platform's report-sharing functionality. A low-privileged user can retrieve report data from shared links, accessing content outside the intended scope of the link's sharing permissions. This is an access control flaw (CWE-863) affecting the platform's data confidentiality posture. As of the latest tracking, no vendor patch exists (patch confidence 0/4), leaving all HackerOne-hosted vulnerability reports susceptible to potential unauthorized disclosure. The EPSS score of 0.00236 indicates low immediate exploitation likelihood, but the severity is elevated given the sensitive nature of vulnerability reports.

Technical Analysis

CVE-2026-64630 resides in the HackerOne platform's shared report link mechanism. When a user generates a shareable link for a vulnerability report (typically via the "Share" feature), the server-side access control logic fails to properly validate that the requesting principal (the user who opens the link) has permission to view ALL fields and attachments included in the report resource.

The vulnerability is rooted in a broken authorization check (CWE-863 — Incorrect Authorization). The HackerOne application likely performs authorization checks on the report object itself, but fails to enforce granular, per-field or per-child-resource access controls. When a report is rendered through a shared link, the API endpoint serving the data performs a single coarse-grained permission check (e.g., "does user X have access to report Y?"), but then serializes the entire report payload — including private comments, internal team notes, redacted severity assessments, and attachments — to the client response without filtering based on the specific sharing scope selected by the original reporter.

Attack surface: Authenticated low-privileged users (e.g., a hacker with a "reporter" or "participant" role on one report) can craft or manipulate requests to the platform's report-access endpoints. The affected endpoints are those that accept a report ID or a share token and return JSON with report contents. Because the vulnerability requires an authenticated session, it is not a network-accessible remote code execution, but rather a horizontal privilege escalation / confidentiality breach within the platform's tenant boundaries.

No specific version range is disclosed (affected versions: []), which strongly suggests the vulnerability exists at the service/application level rather than in a versioned software package. The CNA title field is blank, and the vendor fix is N/A, reinforcing that this is a live SaaS issue without a released patch artifact.

The attack vector is network-based (AV:N) requiring authentication (PR:L) with no user interaction (UI:N), and the primary impact is confidentiality (C:H), with integrity (I:N) and availability (A:N) unaffected.

Exploitation Scenarios

Scenario: Cross-Report Data Exfiltration via Shared Link Abuse

1. Reconnaissance / Target Identification: The attacker is an authenticated HackerOne user with a low-privileged role — e.g., a security researcher who submitted a report. They identify another report (target report) whose content they are not legitimately authorized to view (e.g., a report submitted to a private program by a different researcher, or an internal triage report).

2. Trigger / Weaponization: The attacker requires a valid share token for the target report. They obtain one via social engineering (tricking the report owner into sharing a link) or by predicting/brute-forcing weak token entropy. Alternatively, if the platform's "shared link" feature generates tokens with the report ID embedded, the attacker can manipulate the URL path (e.g., /reports/{id}/share?token=attacker-supplied) or modify the API request body to include the target report ID.

   Specifically, the attacker intercepts a legitimate request they are authorized to make — e.g., GET /api/reports/{their_own_report_id} — and changes the report ID to the target report ID while preserving the share token from their own report. The server-side validation only checks that the sharing feature is enabled and fails to re-validate scope against the new report ID.

3. Payload / Execution: The attacker sends the crafted HTTP request:

   GET /api/v1/reports/98765?_share_token=abc123def456 HTTP/1.1
   Host: hackerone.com
   Authorization: Bearer {attacker-valid-session}
   

   Where 98765 is the target report ID and abc123def456 is the attacker's own valid share token. The server accepts the token, verifies it is a valid token for some report, but incorrectly authorizes access to whatever report ID is in the path.

4. Post-Exploitation Impact: The response returns the full JSON with the target report's title, description, vulnerability details (including unique exploits or proof-of-concept code), affected asset URLs, internal comments, and any attached files (as base64). The attacker exfiltrates this data. With access to award amounts and program-specific vulnerability details, the attacker can:

   • Re-report the vulnerability to a competing program for bounty duplication.
   • Disclose the vulnerability publicly before it's patched, forcing the vendor to pay extortion or accelerating risk.
   • Steal trade secrets of the affected vendor if the report contains proprietary code.

Impact Assessment

Business Impact: High confidentiality loss for the HackerOne platform and its clients (enterprise organizations running bug bounty programs). Vulnerability reports contain highly sensitive information — zero-day exploit techniques, internal network architectures, and source code snippets. Unauthorized disclosure could:

• Lead to exploitation of the same vulnerability by malicious actors before a vendor patch is deployed.
• Damage the trust relationship between program owners and researchers.
• Violate GDPR/other data protection regulations if the report contains PII (e.g., researcher email addresses, real names).

Affected Systems: All organizations running bug bounty programs on the HackerOne platform, and all security researchers with accounts. Blast radius is a multi-tenant data breach confined to the HackerOne application level.

CVSS Subscores: While the official CVSS vector is N/A, applying the known MITRE/CWE analysis, the vector would approximate CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:N/A:N — resulting in a Base Score of approximately 6.5 (Medium). The EPSS percentile of 14.6% indicates low current exploitation in the wild, but this is expected for a recent or poorly-documented CVE.

Detection Guidance

Sigma Rule

title: HackerOne Shared Report Link Authorization Bypass Attempt
id: 3a8f2c1e-4b5d-4e6f-9a0b-1c2d3e4f5a6b
status: experimental
description: Detects attempts to access HackerOne report data via shared link with modified report IDs, indicating a possible CVE-2026-64630 exploitation attempt.
logsource:
  category: web
  product: proxy
detection:
  selection:
    cs-host|endswith: 'hackerone.com'
    cs-method: 'GET'
    cs-uri-path|startswith: '/api/'
    cs-uri-path|contains: 'reports/'
    cs-uri-query|contains: '_share_token='
  filter:
    cs-uri-path|startswith: '/api/unauthorized_reports/'  # Internal operational path
  condition: selection and not filter
level: high
falsepositives:
  - Legitimate sharing by the report owner within scope
  - Automated platform processes that interlink reports
tags:
  - attack.t1190
  - cve.2026.64630

YARA Rule

rule HackerOne_SharedLink_AuthBypass
{
    meta:
        author = "ValtersIT Research"
        description = "Detects API responses indicative of CVE-2026-64630 exploitation - full report data returned without proper scope validation"
        cve = "CVE-2026-64630"
        date = "2026-01-15"
        severity = "high"
    strings:
        $endpoint = "reports/" ascii nocase
        $share_token = "_share_token" ascii nocase
        $report_field = "\"report_description\"" ascii
        $private_comment = "\"internal_note\"" ascii
        $attachments = "\"attachments\"" ascii
        $success = "HTTP/1.1 200" ascii
    condition:
        $endpoint and $share_token and 2 of ($report_field, $private_comment, $attachments) and $success
}

Suricata IDS Rule

alert http any any -> any any (msg:"ET EXPLOIT HackerOne CVE-2026-64630 Shared Report Link Auth Bypass"; flow:established,to_server; content:"GET"; http_method; content:"hackerone.com"; http_host; content:"/api/"; http_uri; content:"reports/"; http_uri; pcre:"/\/api\/[^\/]+\/reports\/\d+\?_share_token=[a-f0-9]+/Ui"; sid:202664630; rev:1; classtype:attempted-user; reference:cve,2026-64630; metadata:attack_target Web_Application, created_at 2026_01_15, deployment Perimeter, signature_severity High, tag Auth_Bypass;)

Elastic Detection

sequence by source.ip with maxspan=2s
  [http where url.domain == "hackerone.com" and url.path like "*reports/*" and url.query like "*_share_token=*"]
  [http where url.domain == "hackerone.com" and url.path like "*/reports/*" and method == "GET"]
  [network where direction == "egress" and destination.port == 443 and length > 50000]  // Large response exfiltration

Splunk SPL Query

index=web sourcetype=access_combined
| where "hackerone.com" IN (host, uri_domain)
| regex uri_path="\/api\/.*\/reports\/\d+"
| regex uri_query="_share_token="
| eval report_id = replace(uri_path, "^.*\/reports\/(\d+)$", "\1")
| stats count by clientip, report_id, status
| where count > 2  // Repeated attempts on same report
| table _time, clientip, report_id, count, status

Wazuh OSSEC Rule

<group name="web,accesslog,exploit,">
  <rule id="743896" level="10">
    <decoded_as>json</decoded_as>
    <field name="url">\.*\/api\/.*\/reports\/\d+\?_share_token=.*</field>
    <field name="host">hackerone\.com</field>
    <description>HackerOne CVE-2026-64630 shared link authorization bypass attempt</description>
    <mitre>
      <id>T1190</id>
    </mitre>
    <group>exploit_attempt</group>
  </rule>
</group>

Mitigation & Patch Guidance

Patch Confidence: 0/4 — UNPATCHED

There is currently no vendor patch available for CVE-2026-64630. The affected versions list is empty, and no vendor fix or workaround has been published. Organizations using HackerOne cannot remediate this at the code level and must rely on platform-side controls and compensating measures.

1. Immediate Mitigations (Platform Administrators):

• Disable or restrict the shared-link feature on all programs if the platform settings allow this administrative override. If HackerOne exposes a feature flag for "external report sharing," turn it OFF globally.
• Restrict report visibility to approved researchers only. Review all program settings and ensure that "participants" cannot view reports they were not added to — enforce a strict "invitation-only" participation model.
• Enable 2FA on all platform accounts to reduce the risk of legitimate account takeover that could be used to pivot into the shared-link flaw.

2. Patch/Upgrade Steps:

• Monitor the HackerOne status page and security advisory mailing list for CVE-2026-64630 patch announcements.
• Subscribe to the NVD CVE feed for CVE-2026-64630 to receive automated notifications when a vendor fix is linked.
• When a patch is released, HackerOne will apply it server-side; no client-side upgrade is needed. Validate the fix by attempting to share a report and accessing it with a second low-privileged account — verify that only the intended report is returned.

3. Long-Term Hardening (For Enterprise Security Teams):

• API request logging: Ensure your organization's web proxy (Palo Alto, Zscaler, etc.) is configured to log all hackerone.com API traffic. Use the Sigma/Splunk rules above to build a detection pipeline for this vulnerability class.
• Contractual controls: If your organization runs a bounty program on HackerOne, require in the service agreement that HackerOne maintains valid CWE-863 controls and timely disclosure of authorization bugs.
• Data minimization: Instruct your program managers to avoid pasting full internal details or credentials into HackerOne reports. Encourage the use of secure external links (e.g., private file storage) rather than inline attachments.
• Researcher vetting: Restrict participation to vetted researchers to reduce the pool of low-privileged users who could exploit this flaw.

References

1. NVD Entry for CVE-2026-64630: https://nvd.nist.gov/vuln/detail/CVE-2026-64630 — Official NVD record; current CVSS score is N/A; references the CWE-863 classification.
2. CVE.org Record: https://www.cve.org/CVERecord?id=CVE-2026-64630 — MITRE CVE record with CNA information and affected vendor status.
3. HackerOne Security Advisories: https://hackerone.com/security-advisories — Vendor advisory hub; monitor for a future advisory tied to CVE-2026-64630.
4. FIRST EPSS: https://www.first.org/epss/search?cve=CVE-2026-64630 — EPSS score 0.00236 (14.6th percentile), indicating a low probability of exploitation in the next 30 days.
5. CWE-863 — Incorrect Authorization: https://cwe.mitre.org/data/definitions/863.html — Weakness reference; describes the improper validation of authorization levels.

Exploit-in-the-Wild Evidence: No known threat actor campaigns have been publicly attributed to CVE-2026-64630. CISA KEV does not list this CVE. Public PoC/exploit code is available (PoC status: Public), but no Nuclei template or weaponized exploit has been published. The lack of patch data and the low EPSS percentile suggest that the public PoC may be limited or non-functional against the live platform, which could rotate tokens or have other mitigating controls not yet documented.