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Fencer Vulns
high 8.8

CVE-2026-40308 json

My Calendar: Unauthenticated Information Disclosure (IDOR) via Multisite switch_to_blog

published 2026-04-16 6 mo ago modified 2026-06-17 4 mo ago also EUVD-2026-23306 , GHSA-2mvx-f5qm-v2ch

cvss
8.8
version 4.0, CNA
cisa kev
Not listed
not in CISA's catalog
epss
0.9%
EPSS 0.9% chance of exploitation in 30 days, percentile 60%
public exploits
0
none known, plus a Nuclei check

Summary

My Calendar is a WordPress plugin for managing calendar events. In versions 3.7.6 and below, the mc_ajax_mcjs_action AJAX endpoint, registered for unauthenticated users, passes user-supplied arguments through parse_str() without validation, allowing injection of arbitrary parameters including a site value. On WordPress Multisite installations, this enables an unauthenticated attacker to call switch_to_blog() with an arbitrary site ID and extract calendar events from any sub-site on the network, including private or hidden events. On standard Single Site installations, switch_to_blog() does not exist, causing an uncaught PHP fatal error and crashing the worker thread, creating an unauthenticated denial of service vector. This issue has been fixed in version 3.7.7.

Patch / fix

  • packagist joedolson/my-calendar 3.7.7
  • joedolson my_calendar 3.7.7

CISA SSVC

Exploitation
Proof of concept is public
Automatable
yes
Technical impact
total
Assessed
6 mo ago

Exploit prediction

0.93% chance of exploitation in the next 30 days, higher than 60% of all scored CVEs (FIRST EPSS, 2026-11-08).

Exploits and checks

  • Nuclei template My Calendar WordPress Plugin - Information Disclosure nuclei detection template
  • github.com https://github.com/joedolson/my-calendar/security/advisories/GHSA-2mvx-f5qm-v2ch referenced PoC, tagged "exploit" by a source, unverified

CVSS scores

assigned by version score vector
CNA 4.0 8.8 CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:H/VI:N/VA:H/SC:N/SI:N/SA:N
CNA 4.0 8.8 CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:H/VI:N/VA:H/SC:N/SI:N/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X

Affected packages

ecosystem package affected fixed in
packagist joedolson/my-calendar
<3.7.7
3.7.7

Affected products

  • joedolson my-calendar

Classification

Weakness
  • CWE-639 Authorization Bypass Through User-Controlled Key
Technology feeds

References

Sources

Fencer Vulns keeps one entry per vulnerability: the CVE id wins, then GHSA, and records that alias each other are merged, except that two CVEs always keep separate entries. The same data is available as JSON.

CPEs and fixed versions use Anchore's correction of NVD's data: Added CPE configurations because not yet analyzed by NVD.