---
id: CVE-2026-52767
title: YesWiki is a wiki system written in PHP
summary: >-
  YesWiki is a wiki system written in PHP. From version 4.6.2 to before version
  4.6.6, HttpSignatureService::verifySignature() checks the result of PHP's
  openssl_verify() with a loose boolean negation - if (!openssl_verify(...)) {
  throw ..…
severity: high
cvss: 8.2
cvssVector: 'CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:L'
cwe:
  - CWE-347
vendor: YesWiki
product: yeswiki
affected:
  - 'yeswiki >= 4.6.2, < 4.6.6'
patched:
  - yeswiki/yeswiki 4.6.6
published: '2026-09-05'
updated: '2026-09-08'
sourceUpdated: '2026-09-08T21:05:26.920'
source: NVD
sourceUrl: 'https://nvd.nist.gov/vuln/detail/CVE-2026-52767'
references:
  - url: >-
      https://github.com/YesWiki/yeswiki/commit/d1795e0301e1a1078f17b4b98f56fff70de2029e
    label: security-advisories@github.com
  - url: 'https://github.com/YesWiki/yeswiki/releases/tag/v4.6.6'
    label: security-advisories@github.com
  - url: 'https://github.com/YesWiki/yeswiki/security/advisories/GHSA-mv28-wj57-f57g'
    label: security-advisories@github.com
  - url: 'https://github.com/YesWiki/yeswiki/security/advisories/GHSA-mv28-wj57-f57g'
    label: 134c704f-9b21-4f2e-91b3-4a467353bcc0
  - url: 'https://github.com/advisories/GHSA-mv28-wj57-f57g'
tags:
  - nvd
  - cve.org
  - exploit-available
  - ghsa
  - composer
epss: 0.00352
epssPercentile: 0.26117
aliases:
  - GHSA-mv28-wj57-f57g
ecosystem: composer
exploitAvailable: true
ssvc:
  exploitation: poc
  automatable: 'yes'
  technicalImpact: partial
  timestamp: '2026-09-08T17:51:20.326023Z'
ingestedAt: '2026-07-09T21:52:34.694Z'
---

## Overview

YesWiki is a wiki system written in PHP. From version 4.6.2 to before version 4.6.6, HttpSignatureService::verifySignature() checks the result of PHP's openssl_verify() with a loose boolean negation - if (!openssl_verify(...)) { throw ... }. PHP's openssl_verify has four possible return values: 1, 0, -1, and "false". The -1 row is the bypass: PHP's truthiness rules make -1 a truthy value, so !(-1) === false, the throw is skipped, and the controller proceeds to processActivity(). Any condition that makes OpenSSL's EVP_VerifyFinal() return -1 triggers the bypass. The reachable consequence is the controller silently treats a failed verification as success and processes the attacker's payload. This issue has been patched in version 4.6.6.

## Remediation

Refer to the linked advisories for vendor-supplied fixes and affected version ranges.

## Package advisory (CVE-2026-52767)

Affected packages:

- `yeswiki/yeswiki >= 4.6.2, < 4.6.6`

Patched in:

- `yeswiki/yeswiki 4.6.6`

Source: https://github.com/advisories/GHSA-mv28-wj57-f57g