CVE-2026-75689

Executive Summary

CVE-2026-75689 is a stored Cross-Site Scripting (XSS) vulnerability in Adobe Connect, rated CVSS 9.3 (Critical). An unauthenticated attacker can inject malicious JavaScript into vulnerable form fields; that script is later executed in the browser of any user who views the affected page, potentially granting the attacker elevated access to or control over the victim's account or session. Adobe Connect is widely deployed for enterprise web conferencing, virtual classrooms, and eLearning, so successful exploitation can compromise privileged meeting hosts, administrators, and authenticated participants across a tenant.

Technical Analysis

The vulnerability class is CWE-79, Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting'), specifically the stored (persistent) variant. Per the NVD description, the flaw resides in "vulnerable form fields" — attacker-supplied input is persisted server-side without adequate output encoding, and is subsequently rendered into a page served to other users. When a victim browses to the page containing the vulnerable field, the injected script executes in the origin of the Adobe Connect application, in the victim's authenticated browser context.

The CVSS vector CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:H/I:H/A:N is highly diagnostic of the mechanics:

• AV:N / AC:L / PR:N — the vulnerable interface is network-reachable, no special conditions are required to attempt injection, and the attacker needs no prior account or privileges on the platform to submit the malicious field content in the general case.
• UI:R — exploitation requires a victim to navigate to the page containing the tainted field. Attacker effectiveness therefore depends on lure delivery (meeting invitations, shared links, e-mail to participants), not on victim-side software faults.
• S:C (Scope Changed) — the most significant component. Script execution is not contained to the vulnerable component; the injected code acts with privileges of a different security authority than the vulnerable form handling. In an XSS context this reflects the attacker's script inheriting the victim's full authenticated session and origin privileges, crossing the intended trust boundary between the untrusted input channel and the application's privileged UI.
• C:H / I:H / A:N — total loss of confidentiality and integrity, no availability impact. This is the classic persistent-XSS profile: read anything the victim can read (meeting records, stored files, directory and profile data), perform anything the victim can perform (account, meeting, and administrative actions), but no guaranteed denial of service.

Because the payload is stored, no crafted URL is needed at execution time — the tainted field remains in the application's data store and re-fires on every subsequent page view, providing repeatable, multi-victim detonation from a single injection.

Insufficient technical detail is available in the provided intelligence to identify the specific vulnerable endpoint, parameter, or validation routine. No CNA title, affected version range, OSV package data, Nuclei template, or public PoC was supplied. All analysis below is therefore conducted at the vulnerability-class level.

Exploitation Scenarios

1. Reconnaissance / target identification. The attacker identifies a reachable Adobe Connect deployment — typically via web fingerprinting of login, meeting, or content pages — and locates a form field whose submitted value is later displayed to other users (for example, a name, title, comment, or similar free-text display field). No authentication is assumed necessary per PR:N.

2. Trigger of the specific flaw class (stored XSS). The attacker submits crafted HTML/JavaScript-bearing content into the vulnerable form field. Because the application fails to neutralize the input before persistence, the script is stored server-side rather than being rejected or encoded. This step is the injection half of the classic stored-XSS chain and succeeds without any victim interaction.

3. Payload / execution method (vulnerability-class level). When any user — participant, meeting host, or administrator — browses to the page that renders the tainted field, the stored script is emitted into the response and executes in that user's browser within the Adobe Connect origin. No publicly available PoC exists for this CVE; the execution path is inferred strictly from the documented stored-XSS mechanism in the NVD description.

4. Post-exploitation impact. The script runs with the victim's authenticated session context. Because the CVSS scope is Changed with High confidentiality and integrity impact, the attacker can perform any action the victim's account is authorized to perform — reading data visible to that account and issuing state-changing requests as that user — and can exfiltrate the session to the attacker. For privileged victims (meeting hosts, administrators), this escalates to control over meetings, content, and potentially tenant-level configuration. A:N confirms the vulnerability is not expected to cause denial of service.

Impact Assessment

With a base score of 9.3, this is a Critical-severity issue. The NVD description explicitly warns of "potentially gaining elevated access or control over the victim's account or session," which is consistent with the CVSS subscores: Confidentiality High and Integrity High under a Changed scope, and no Availability impact. The required user interaction (UI:R) is the only moderating factor.

Business impact centers on Adobe Connect's role as a trusted corporate communications channel. A stored XSS payload in a meeting or content field can:

• Harvest and reuse authenticated sessions of meeting hosts, instructors, and administrators.
• Manipulate or exfiltrate meeting content, participant data, and stored materials within the victim's authorization scope.
• Serve as a pivot for further internal phishing or malware delivery from a trusted, allow-listed SaaS origin.

Blast radius equals every user who views the page containing the tainted field — the persistence means one injection can compromise many victims without repeated attacker action. Because no CISA KEV entry, no EPSS score, and no public exploit or Nuclei template currently exist, there is no confirmed in-the-wild exploitation evidence at the time of writing; however, the low complexity and network reachability make weaponization straightforward once the vulnerable field is identified.

Detection Guidance

Sigma Rule

title: Potential Stored XSS Injection Attempt Against Adobe Connect Form Fields
id: 9c1f7a52-4b3e-4d0a-9f21-7e6a8c2b5d10
status: experimental
description: Detects script-tag or event-handler payloads submitted to Adobe Connect form fields, consistent with CVE-2026-75689 stored XSS exploitation.
references:
  - https://nvd.nist.gov/vuln/detail/CVE-2026-75689
author: Threat Intelligence
date: 2026/01/01
logsource:
  category: webserver
detection:
  selection_method:
    cs-method:
      - 'POST'
      - 'PUT'
  selection_payload:
    - 'cs-uri-query|contains':
        - '<script'
        - 'javascript:'
        - 'onerror='
        - 'onload='
        - '<svg'
    - 'cs-uri-query|contains|all':
        - '<'
        - '>'
  condition: selection_method and selection_payload
falsepositives:
  - Legitimate rich-text or HTML content submission in fields that permit markup
  - Security scanners and authorized penetration tests
level: medium
tags:
  - attack.t1189
  - cve.2026.75689

YARA Rule

rule CVE_2026_75689_AdobeConnect_Stored_XSS
{
    meta:
        description = "Detects stored XSS payload markers associated with CVE-2026-75689 in Adobe Connect form-field content"
        author = "Threat Intelligence"
        reference = "https://nvd.nist.gov/vuln/detail/CVE-2026-75689"
        date = "2026-01-01"
        severity = "high"

    strings:
        $s1 = "<script" ascii nocase
        $s2 = "javascript:" ascii nocase
        $s3 = "onerror=" ascii nocase
        $s4 = "onload=" ascii nocase
        $s5 = "document.cookie" ascii nocase
        $s6 = "<svg" ascii nocase
        $s7 = "String.fromCharCode" ascii nocase

    condition:
        uint16(0) == 0x3C3F or 2 of ($s*)
}

Suricata IDS Rule

alert http any any -> any any (msg:"CVE-2026-75689 Adobe Connect Stored XSS Injection Attempt"; flow:established,to_server; http.method; content:"POST"; http.header; content:"Adobe Connect"; nocase; http.request_body; content:"<script"; nocase; http.request_body; content:"onerror="; nocase; http.request_body; content:"javascript:"; nocase; threshold:type limit, track by_src, count 1, seconds 60; sid:202675689; rev:1; classtype:web-application-attack; reference:cve,2026-75689; reference:url,nvd.nist.gov/vuln/detail/CVE-2026-75689; metadata:service http;)

Elastic Detection

sequence by source.ip with maxspan=5m
  [ network where network.protocol == "http" and http.request.method == "POST" and
    http.request.body.text contains "<script" ]
  [ network where network.protocol == "http" and http.request.method == "POST" and
    (http.request.body.text contains "onerror=" or http.request.body.text contains "javascript:") ]

Splunk SPL Query

index=web OR index=proxy sourcetype=access_combined OR sourcetype=stream:http
| eval body=coalesce(form_data, uri_query, request_body)
| where (method="POST" OR method="PUT") AND match(body, "(?i)(<script|javascript:|onerror=|onload=)")
| stats count min(_time) as first_seen max(_time) as last_seen values(uri) as target_uris by src_ip, dest_host
| where count > 1
| sort - count
| table first_seen, last_seen, src_ip, dest_host, target_uris, count

Wazuh OSSEC Rule

<group name="web,appsec,adobe_connect,">
  <rule id="2026758" level="10">
    <decoded_as>web-accesslog</decoded_as>
    <if_sid>31100</if_sid>
    <method>POST|PUT</method>
    <url_contains>adobe</url_contains>
    <regex type="pcre2">(?i)(&lt;script|javascript:|onerror=|onload=)</regex>
    <description>CVE-2026-75689: Possible stored XSS payload submitted to Adobe Connect form field</description>
    <mitre>
      <id>T1189</id>
    </mitre>
    <group>cve_2026_75689,attack,</group>
  </rule>
</group>

Mitigation & Patch Guidance

Patch confidence: 0/4 (UNPATCHED — no patch evidence from any tracked source). No vendor fix, workaround, or affected version range was provided in the source intelligence. The guidance below is class-level for stored XSS and should be validated against any subsequent Adobe advisory.

1) Immediate mitigations

• Deploy a WAF or reverse-proxy rule that neutralizes or rejects HTML/JavaScript markup (<script, event handlers such as onerror/onload, javascript: URIs) in form-field submissions and blocks it on response rendering.
• Where the operational profile permits, restrict public/guest access to form-field submission paths pending a fix.
• Enforce Content-Security-Policy headers that prohibit inline and third-party script on application responses to reduce residual XSS execution.
• Remind users to avoid clicking unsolicited meeting or content links delivered from unknown senders (the UI:R requirement makes lure delivery a core control point).

2) Patch / upgrade steps

• Monitor the Adobe Product Security Bulletin feed (helpx.adobe.com/security) for the assigned APSB advisory covering CVE-2026-75689 and apply the fixed build as soon as it is released.
• Until then, treat all deployments as unpatched and rely on the compensating controls above.
• After upgrading, re-test the form fields that previously accepted and rendered user content to confirm output encoding is effective.

3) Long-term hardening

• Apply contextual output encoding for all user-supplied data rendered into HTML, and validate/normalize input at the server boundary.
• Adopt an allow-list policy (for example, a sanitizer with strict tag/attribute filtering) for any field intended to carry rich content.
• Deploy CSP with nonces and no unsafe-inline as a defense-in-depth layer against stored XSS classes generally.
• Monitor for re-injection: since stored payloads persist, ensure any identified tainted records are purged from storage as part of incident response.

References

• NVD — CVE-2026-75689: https://nvd.nist.gov/vuln/detail/CVE-2026-75689
• MITRE CWE-79 — Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting'): https://cwe.mitre.org/data/definitions/79.html
• Adobe Product Security Bulletins (vendor advisory feed; verify APSB entry for CVE-2026-75689): https://helpx.adobe.com/security.html
• FIRST — EPSS model documentation (no score currently assigned for this CVE): https://www.first.org/epss/
• CISA Known Exploited Vulnerabilities Catalog (CVE-2026-75689 not currently listed): https://www.cisa.gov/known-exploited-vulnerabilities-catalog

No public proof-of-concept, Nuclei template, or exploit code was identified. No CISA KEV listing, EPSS score, or threat-actor campaign has been associated with CVE-2026-75689 at the time of writing.