CVE-2025-26042Public exploitNetwork attack vector

Service freeze via notification URL backtracking

Published Mar 17, 2025 · Updated Jan 26, 2026

Regular expression denial of service in Uptime Kuma allows remote authenticated users to freeze the web service through notification URLs. The PushDeer and Whapi providers strip trailing slashes with an end-anchored greedy expression that catastrophically backtracks on long slash runs followed by a non-slash. Administrator access to create or test a notification is required; affected releases are 1.15.0 through 1.23.16 and 2.0.0-beta.0 through 2.0.0-beta.1, and exploitation consumes CPU and delays or freezes the service.

CVSS severity6.7
Medium
EPSS probability0.38%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Regular expression denial of service in Uptime Kuma allows remote authenticated users to freeze the web service through notification URLs. The PushDeer and Whapi providers strip trailing slashes with an end-anchored greedy expression that catastrophically backtracks on long slash runs followed by a non-slash. Administrator access to create or test a notification is required; affected releases are 1.15.0 through 1.23.16 and 2.0.0-beta.0 through 2.0.0-beta.1, and exploitation consumes CPU and delays or freezes the service.

The record

CVE
CVE-2025-26042
Published
Mar 17, 2025
Updated
Jan 26, 2026
Vendor
Unknown vendor
Product
Unknown product
Classifications
CWE-1333, T1499.004
Attack vector
network
Privileges
admin

Timeline

How it unfolded

  1. Mar 17, 2025CVE publishedPublication date reported by the CVE source.
  2. Jan 26, 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?

Affected buildAffected product and version details are unavailable.

What conditions does exploitation require?

Attack vectornetwork
Required privilegesadmin

What is affected?

Affected products and versions are unavailable in this record.

Published CVSS scores

6.7GitHubCVSS:4.0/AV:N/AC:L/AT:N/PR:H/UI:A/VC:N/VI:N/VA:H/SC:L/SI:L/SA:L
6.0CISA-ADPCVSS:3.1/AV:N/AC:H/PR:H/UI:R/S:U/C:L/I:H/A:H

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 10, 2026Sep 16, 2026
Latest reporting daySep 16, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesadmin
Known exploitationUnconfirmed
Public exploitPublished

Weakness, pattern, technique

CWE-1333Inefficient Regular Expression Complexity
T1499.004Endpoint Denial of Service: Application or System Exploitation

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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