CVE-2026-104454
Deferred Deferred - Pending Action

Algorithmic Complexity DoS in YesWiki Markdown-Link Regex

Publication date: 2026-10-02

Last updated on: 2026-10-02

Assigner: VulnCheck

Description
YesWiki before 4.6.7 contains an algorithmic-complexity denial of service in the wakka.php formatter due to an O(n^2) markdown-link regex. Unauthenticated attackers can submit a small crafted body of bracket characters to the page-edit preview endpoint to pin PHP-FPM workers and saturate the pool.

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Meta Information

Published
2026-10-02
Last Modified
2026-10-02
Generated
2026-10-02
AI Q&A
2026-10-02
EPSS Evaluated
N/A
NVD
CVE-2026-104454
EUVD
EUVD-2026-91465

Affected Vendors & Products

Showing 1 associated CPE
Vendor Product Version / Range
yeswiki yeswiki to 4.6.7 (exc)

Helpful Resources

Exploitability

CWE
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KEV
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CWE ID Description
CWE-1333 The product uses a regular expression with an inefficient, possibly exponential worst-case computational complexity that consumes excessive CPU cycles.

Attack-Flow Graph

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Executive Summary

YesWiki before version 4.6.7 has a vulnerability where an inefficient O(n^2) markdown-link regex in the wakka.php formatter causes a denial of service. Attackers can send a small crafted input of bracket characters to the page-edit preview endpoint, causing PHP-FPM workers to consume excessive CPU resources and become unresponsive.

Detection Guidance

Monitor PHP-FPM worker saturation and high CPU usage during page-edit preview requests. Check for repeated requests with large bracket character payloads to the wakka.php endpoint. Use tools like netstat or ss to observe connection pools.

Impact Analysis

This vulnerability can lead to service disruption by saturating PHP-FPM worker pools, making the website unavailable. Attackers can exploit it without authentication, and even small crafted requests can pin workers for extended periods, causing downtime during sustained attacks.

Compliance Impact

This vulnerability primarily causes denial of service by exhausting server resources, which could lead to system unavailability. While it does not directly expose or leak data, prolonged downtime could impact compliance with regulations requiring timely access to systems or data, such as GDPR's availability principles or HIPAA's access controls. However, the CVE data does not provide specific compliance impacts beyond service disruption.

Mitigation Strategies

Upgrade YesWiki to version 4.6.7 or later if available. If no patch exists, implement input-length caps in the formatter or modify the regex to use possessive quantifiers. Block or rate-limit requests to the wakka.php edit-preview endpoint.

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