CVE Intelligence
Critical Privilege escalation

CVE-2026-104798 — My Calendar <= 3.8.7 - Unauthenticated Privilege Escalation to 'mcs' Parameter via Reflected Shortcode Injection into 'above' Attribute

The My Calendar – Accessible Event Manager plugin for WordPress is vulnerable to Privilege Escalation in all versions up to, and including, 3.8.7. The public `mcs` GET parameter is reflected into post content unsanitized before WordPress core's `do_shortcode` filter runs, allowing an unauthenticated attacker to inject a nested `[my_calendar above=...]` shortcode; `mc_generate_calendar_nav()` then splits the `above` attribute on commas and dispatches each element via `call_user_func()` with no authentication, authorization, or callable allowlist check. This makes it possible for unauthenticated attackers to invoke arbitrary loaded PHP functions, enabling a call chain in which the shortcode `$params` array is passed to `edit_user()` — which PHP coerces to integer `1` as the `$user_id` argument — overwriting the credentials of the initial Administrator account (user ID 1) and granting the attacker full wp-admin access. Exploitation is trivially reachable via the plugin's auto-generated `/my-calendar/` page, which is publicly accessible by default upon plugin activation.

Published Oct 16, 2026 · Updated Oct 16, 2026 · Sources: CVE Program (cve.org) e CISA ADP, NIST National Vulnerability Database · CNA: Wordfence

Who exploits it and how urgent it is

A 0–100 score combining confirmed exploitation, ransomware and APT use, public exploits, EPSS and severity.

No exploitation signal in the sources consulted so far.
How the score was calculated
  • EPSS 0.9% (30-day exploitation probability)+9
  • Technical severity (critical)+10
  • Automatable exploitation (SSVC)+3

The score orders the patch queue; it does not replace your asset context (internet exposure, criticality, compensating controls).

Triage

Is it exploited, how likely is exploitation, what does it touch, and how severe do the sources call it.

Exploitation
Not confirmed
Not in CISA KEV — an absence of record, not proof it is unexploited.
EPSS FIRST
0.89%
ahead of 59% of scored CVEs · Oct 16, 2026
Affects
Joedolson
My Calendar – Accessible Event Manager
CVSS base
9.8
Critical · 2 source(s)

CISA SSVC assessment CISA

Three decision points CISA publishes for the CVEs it assesses (SSVC 2.0.3). A stakeholder decision, not a severity score.

Exploitation
None
none · proof-of-concept · active
Automatable
Yes
can an attacker script the kill-chain steps
Technical impact
Total
partial · total control of the vulnerable component

Remediation

Fixes and mitigations documented by the sources — linked to the original advisory.

No fix documented by the sources we poll. That does not mean none exists: check the vendor advisory.

First 24 hours

Ordered from the record’s own fields — exposure first, because you cannot patch what you have not found. A rule-generated starting point.

  1. Identify exposed assets running the affected vendor/product/version combinations (Joedolson My Calendar – Accessible Event Manager).
  2. The attack is network-based and needs no privileges: restrict exposure (ACLs, VPN, WAF) until patched.
  3. No fix documented in the sources: reduce exposure and monitor the vendor advisory.
  4. Search available logs for exploit probes matching the vulnerability class (privilege escalation), errors and authentication anomalies.

Affected scope

Vendor, product and versions as the sources word them.

VendorProductVersionsStatusSource
Joedolson My Calendar – Accessible Event Manager ≤ 3.4.24≥ 3.5 and ≤ 3.5.21≥ 3.6 and ≤ 3.6.17≥ 3.7 and ≤ 3.7.17≥ 3.8 and ≤ 3.8.7 Vulnerable CVE Program (cve.org) e CISA ADP

Attack characteristics

The CVSS vector, decoded. It describes the attack, not your exposure to it.

Attack vector
Network
Attack complexity
Low
Privileges required
None
User interaction
None
Scope
Unchanged
Confidentiality
High
Integrity
High
Availability
High

Every base score collected

Sources score independently and may disagree; each row says who scored it and under which version.

ScoreVersionSeverityExpl.ImpactScored by
9.8 CVSS 3.1 Critical 3.9 5.9 security@wordfence.com via NIST National Vulnerability Database
9.8 CVSS 3.1 Critical — — Wordfence via CVE Program (cve.org) e CISA ADP
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H (score shown at the top: security@wordfence.com)

Weakness MITRE

Weakness class according to MITRE’s CWE catalog.

CWE-269 · Improper Privilege Management

Other CVEs with this weakness →

Detection

Read off the CVSS vector and the weakness class. Starting points, not tested rules.

  • Prioritize edge telemetry for the network-reachable component (proxy, WAF, IDS/IPS).
web/proxy/WAF logsnetwork IDS/IPS

Timeline

What happened to this CVE, newest first.

  • 2026
  • SSVC assessment updated
    Oct 16, 2026 · CVE Program (cve.org) e CISA ADP
  • Source status changed · Received → Deferred
    Oct 16, 2026 · NIST National Vulnerability Database
  • Source status changed · Published → Received
    Oct 16, 2026 · NIST National Vulnerability Database
  • Record published
    Oct 16, 2026
  • CVSS changed · 9.8
    Oct 16, 2026 · CVE Program (cve.org) e CISA ADP
  • Source status changed · → Published
    Oct 16, 2026 · CVE Program (cve.org) e CISA ADP
  • Record created in this database
    Oct 16, 2026 · CVE Program (cve.org) e CISA ADP
  • CVE published
    Oct 16, 2026 · Wordfence

Source activity

Repeated readings are counted rather than listed.

  • 1× Official description updated · Oct 16, 2026 – Oct 16, 2026

References

8 on the record

Elsewhere on this site

Joedolson
every CVE for this vendor
Privilege escalation
same class
CWE-269
other pages naming this weakness

Related CVEs (same products)

  • CVE-2026-77187 My Calendar <= 3.8.3 - Authenticated (Contributor+) Stored Cross-Site Scripting via 'before' and 'after' Shortcode Attributes Sep 9, 2026
  • CVE-2026-77186 My Calendar <= 3.8.3 - Authenticated (Contributor+) Stored Cross-Site Scripting via 'fallback' Shortcode Attribute Sep 9, 2026
  • CVE-2026-6854 My Calendar <= 3.7.8 - Unauthenticated SQL Injection via 'mc_auth' and 'mc_host' Parameters Jul 8, 2026
  • CVE-2026-11896 My Calendar <= 3.7.14 - Insecure Direct Object Reference to Unauthenticated Sensitive Information Disclosure via 'vcal' Parameter Jul 2, 2026
  • CVE-2026-7525 My Calendar <= 3.7.9 - Authenticated (Custom+) Missing Authorization to Unauthorized Event Publication via 'event_approved' Parameter May 14, 2026
  • CVE-2026-2355 My Calendar – Accessible Event Manager <= 3.7.3 - Authenticated (Contributor+) Stored Cross-Site Scripting via Shortcode Attributes Mar 4, 2026

Not in any source we poll

Listed rather than left blank: an empty field and an unmeasured one look identical on screen, and only one is a reason to look elsewhere.

  • No fixed version, patch or mitigation documented.
  • No confirmed IOCs, IP addresses, domains, file hashes, or malware artifacts supplied.
  • No organization-specific asset inventory, compensating-control status, or patch deployment evidence supplied.
  • No exploit packet captures, log samples, or incident case IDs supplied.

Answered from this record

Text assembled only from the fields above — no additional claims.

What should defenders know first?

CVE-2026-104798 is "My Calendar <= 3.8.7 - Unauthenticated Privilege Escalation to 'mcs' Parameter via Reflected Shortcode Injection into 'above' Attribute", rated Critical. It affects My Calendar – Accessible Event Manager (Joedolson); versions are in the scope table. It is not in CISA KEV, which does not rule out exploitation. CVSS 9.8 describes technical severity. EPSS 0.89% estimates the probability of exploitation in 30 days; neither replaces your asset context. First verify whether exposed or business-critical assets run the affected versions, apply vendor fixes or mitigations, and preserve logs for review.

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