CVE-2026-77838Network attack vector

Script execution in logging-in users' browsers

Published Aug 28, 2026 · Updated Aug 28, 2026

Cross-site scripting in Tsuyoshi Saito SOY Calendar 2.4.0 and earlier allows remote authenticated users to execute script in a user's browser. Neither JVN nor the developer identifies the affected input, rendering locus, or missing neutralization operation. Exploitation requires low privileges and active interaction by a user logging in; the documented consequence is script execution in that browser context.

CVSS severity4.8
Medium
EPSS probability0.17%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Cross-site scripting in Tsuyoshi Saito SOY Calendar 2.4.0 and earlier allows remote authenticated users to execute script in a user's browser. Neither JVN nor the developer identifies the affected input, rendering locus, or missing neutralization operation. Exploitation requires low privileges and active interaction by a user logging in; the documented consequence is script execution in that browser context.

The record

CVE
CVE-2026-77838
Published
Aug 28, 2026
Updated
Aug 28, 2026
Vendor
Tsuyoshi Saito
Product
SOY Calendar
Classifications
CWE-79
Attack vector
network
Privileges
authenticated

Timeline

How it unfolded

  1. Aug 28, 2026CVE publishedPublication date reported by the CVE source.
  2. Aug 28, 2026Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

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Is a vulnerable build present?

Compare these published version ranges with your installed build and any vendor patches.

  1. Affected versionversion=o <=2.4.0

What conditions does exploitation require?

Attack vectornetwork
Required privilegesauthenticated

What is affected?

Tsuyoshi Saito · SOY Calendarversion=o <=2.4.0

Published CVSS scores

5.4JPCERT/CCCVSS:3.0/AV:N/AC:L/PR:L/UI:R/S:C/C:L/I:L/A:N
4.8JPCERT/CCCVSS:4.0/AV:N/AC:L/AT:N/PR:L/UI:A/VC:N/VI:N/VA:N/SC:L/SI:L/SA:N

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

Daily unique IPsNo honeypot observations are available for this CVE in the selected window.

No observations available

Sep 9, 2026Sep 15, 2026
Latest reporting daySep 15, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-79Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting')

Public exploit references

No public exploit references are available in this record.

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Technologies

Your stack

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Your stack

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