CVE-2026-52767

HIGHPre-NVD 8.28.2—
EchelonGraph scoreMEDIUM confidence

This high-severity CVE scores 8.2 under a secondary CVSS source (NVD's own analysis pending). EPSS exploit probability: 0.2%, top 87% of all CVEs by exploit prediction. GitHub Security Advisory data not yet ingested — confidence will rise once GHSA publishes (typical lag: hours to days for open-source ecosystem CVEs; never for infrastructure-only CVEs).

Triggered by: NVD CVSS baseline
Sources: epss, secondary
Elevated
8.2EG
EchelonGraph verdictPlan a fixSerious severity, but no confirmed exploitation yet.
  • High severity, but no confirmed exploitation yet
CISA-KEV: Not listedEPSS PROB: 0%CVSS: 8.2Exploit: Elevated riskExposed: 0

No vendor fix yet — apply a workaround or compensating control (WAF / firewall / segmentation) and watch for a patch.

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.

CVSS v3
8.2
EG Score
8.2(medium)
EG Risk
68(Attend)
EG Risk 68/100SSVC: Attend

EG Risk is EchelonGraph's 0–100 priority score: it fuses intrinsic severity with real-world exploitation and automatability so you can rank equal-severity CVEs and fix the most dangerous first. Higher = act sooner. Distinct from the 0–10 EG Score (severity).

How it’s computed
Severity82% × 45%
Exploitation40% × 40%
Automatability100% × 15%
Action: Remediate soon — notable exploitation risk.
EPSS PROB
0%
EPSS %ILE
13%
KEV
Not listed

Published

July 9, 2026

Last Modified

September 8, 2026

Advisory Details (3)

Auto-updated Sep 4, 2026
🔬 Proof of concept available. Patch available. Sources: github_commit, github_release, github.
github_release Patch Available

v4.6.6

Patch available: YesWiki/yeswiki v4.6.6

https://github.com/YesWiki/yeswiki/releases/tag/v4.6.6
github_commit Patch Available

commit d1795e0301e1 (YesWiki/yeswiki)

Patch available: YesWiki/yeswiki v4.6.6 (contains commit d1795e0301e1)

https://github.com/YesWiki/yeswiki/commit/d1795e0301e1a1078f17b4b98f56fff70de2029e
github Patch Available🟡 PoC Available

Unauthenticated ActivityPub Signature-Verification Bypass via `!openssl_verify(...)` accepting `int(-1)` · Advisory · YesWiki/yeswiki · GitHub

https://github.com/YesWiki/yeswiki/security/advisories/GHSA-mv28-wj57-f57g

Vendor Advisories for CVE-2026-52767(1)

These vendors published their own advisory mentioning this CVE — often with vendor-specific remediation steps + affected product lists not in NVD.

Affected Packages

(1 across 1 ecosystem)
Packagist(1)
PackageVulnerable rangeFixed inDependents
yeswiki/yeswikiv4.6.2, v4.6.3, v4.6.4, v4.6.54.6.6—

Weakness Classification(1)

MITRE Common Weakness Enumeration — the root-cause categories this CVE belongs to.

Data Freshness Timeline

(refreshed 6× in last 7d / 17× in last 30d)

Each row is a source pipeline that fetched or updated this CVE on that date, with what changed. For example, "NVD update" means NVD published or revised its analysis for this CVE; "MITRE cvelistV5" means we ingested or refreshed it from the CNA feed. Most recent first.

  1. 2026-09-18 19:28 UTCEPSS rescore
  2. 2026-09-18 05:35 UTCEG score recompute
  3. 2026-09-16 14:08 UTCEPSS rescore
  4. 2026-09-16 05:15 UTCEPSS rescore
  5. 2026-09-13 23:45 UTCEG score recompute
  6. 2026-09-13 16:47 UTCEPSS rescore
  7. 2026-09-12 15:06 UTCEG score recompute
  8. 2026-09-12 03:21 UTCEG score recompute
  9. 2026-09-11 14:53 UTCEPSS rescore
  10. 2026-09-10 09:35 UTCEPSS rescore
  11. 2026-09-08 22:54 UTCEG score recompute
  12. 2026-09-08 22:01 UTCEPSS rescore
  13. 2026-09-07 16:01 UTCEPSS rescore
  14. 2026-09-06 13:59 UTCEG score recompute
  15. 2026-09-06 13:47 UTCEPSS rescore
  16. 2026-09-05 22:30 UTCEG score recompute
  17. 2026-09-05 00:19 UTCEG score recompute
  18. 2026-07-30 11:22 UTCEG score recompute
  19. 2026-07-26 12:17 UTCEG score recompute
  20. 2026-07-23 03:19 UTCEG score recompute
  21. 2026-07-09 21:46 UTCEG score recompute

Frequently asked(5)

What is CVE-2026-52767?
CVE-2026-52767 is a high vulnerability published on July 9, 2026. 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 opensslverify() with a loose boolean negation - if (!opensslverify(...)) { throw ... }. PHP's opensslverify has four possible return values: 1, 0,…
When was CVE-2026-52767 disclosed?
CVE-2026-52767 was first published in the National Vulnerability Database on July 9, 2026, with the most recent update on September 8, 2026. EchelonGraph re-ingests CVE updates from NVD on a 2-hour cycle, so this page reflects the latest published state.
Is CVE-2026-52767 actively exploited?
CVE-2026-52767 is not currently on CISA's Known Exploited Vulnerabilities catalog. FIRST EPSS estimates a 0% probability of exploitation in the next 30 days, which ranks it in the top 87.2% of all scored CVEs.
What is the CVSS score of CVE-2026-52767?
CVE-2026-52767 has a CVSS v3 base score of 8.2 (NVD).
How do I remediate CVE-2026-52767?
Patch to the fixed version published by the affected vendor. Where vendor advisories exist for CVE-2026-52767, EchelonGraph cross-links them in the Vendor Advisories panel below — those typically contain the canonical remediation steps, fixed version numbers, and any vendor-specific mitigations.

Dependency Blast Radius

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