CVE-2026-83627Network attack vector

Unauthenticated code execution via debug-log cookie names

Published Sep 5, 2026 · Updated Sep 7, 2026

Code injection in WPMU DEV Hummingbird Performance 3.21.0 and earlier allows remote attackers to execute PHP through a debug log. The log_msg() path writes raw wphb_cache_ cookie names into a web-accessible PHP log after a namespace-mismatched class_exists() check omits its protective die header. Exploitation requires non-default Page Caching and Debug Log settings plus front-end creation or rotation of the log, after which injected PHP runs with the WordPress process's access.

CVSS severity9.8
Critical
EPSS probability0.82%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Code injection in WPMU DEV Hummingbird Performance 3.21.0 and earlier allows remote attackers to execute PHP through a debug log. The log_msg() path writes raw wphb_cache_ cookie names into a web-accessible PHP log after a namespace-mismatched class_exists() check omits its protective die header. Exploitation requires non-default Page Caching and Debug Log settings plus front-end creation or rotation of the log, after which injected PHP runs with the WordPress process's access.

The record

CVE
CVE-2026-83627
Published
Sep 5, 2026
Updated
Sep 7, 2026
Vendor
WPMU DEV
Product
Hummingbird Performance
Classifications
CWE-94, T1190
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Sep 5, 2026CVE publishedPublication date reported by the CVE source.
  2. Sep 7, 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=0 <=3.21.0

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

WPMU DEV · Hummingbird Performanceversion=0 <=3.21.0

Published CVSS scores

9.8Wordfence CNACVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/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.

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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
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-94Improper Control of Generation of Code ('Code Injection')
T1190Exploit Public-Facing Application

Public exploit references

No public exploit references are available in this record.

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Technologies

Your stack

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Your stack

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