CVE-2026-42267Public exploitNetwork attack vector

Client-side formula execution via unsanitized tag names

Published May 8, 2026 · Updated May 8, 2026

Formula injection in Kimai 2.27.0 through 2.53.0 allows remote authenticated users to plant formulas in XLSX timesheet exports. ArrayFormatter.formatValue() joins attacker-controlled tag names with implode() and returns the result without formula neutralization, so OpenSpout creates a FormulaCell for an equals-prefixed value. Exploitation requires ROLE_USER access plus an administrator to export and open the workbook; the formula then executes in the spreadsheet client.

CVSS severity5.7
Medium
EPSS probability0.22%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Formula injection in Kimai 2.27.0 through 2.53.0 allows remote authenticated users to plant formulas in XLSX timesheet exports. ArrayFormatter.formatValue() joins attacker-controlled tag names with implode() and returns the result without formula neutralization, so OpenSpout creates a FormulaCell for an equals-prefixed value. Exploitation requires ROLE_USER access plus an administrator to export and open the workbook; the formula then executes in the spreadsheet client.

The record

CVE
CVE-2026-42267
Published
May 8, 2026
Updated
May 8, 2026
Vendor
Kimai
Product
Kimai
Classifications
CWE-1236, T1204.002
Attack vector
network
Privileges
authenticated

Timeline

How it unfolded

  1. May 8, 2026CVE publishedPublication date reported by the CVE source.
  2. May 8, 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=>= 2.27.0, < 2.54.0

What conditions does exploitation require?

Attack vectornetwork
Required privilegesauthenticated

What is affected?

Kimai · Kimaiversion=>= 2.27.0, < 2.54.0

Published CVSS scores

5.4GitHub, Inc.CVSS:4.0/AV:N/AC:L/AT:N/PR:L/UI:A/VC:N/VI:H/VA:N/SC:N/SI:N/SA:N/E:P
5.7NIST National Vulnerability DatabaseCVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:U/C:N/I:H/A: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.

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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 exploitPublished

Weakness, pattern, technique

CWE-1236Improper Neutralization of Formula Elements in a CSV File
T1204.002User Execution: Malicious File

Public exploit references

Labels summarize the accepted research assessment. They do not indicate a test against your environment.

Technologies

Your stack

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Your stack

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