# CVE-2026-83627: Code injection in Hummingbird Performance – Cache & Page Speed Optimization for Core Web Vitals | Critical CSS | Minify CSS | Defer CSS Javascript | CDN

> Unauthenticated attackers can achieve remote code execution by injecting PHP into a debug log file if page caching debug logging is enabled.

- **Severity:** Critical 9.8 (`CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H`)
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** No
- **Published:** 5 Sep 2026
- **Updated:** 7 Sep 2026
- **Also known as:** GHSA-4rx5-c9jj-cfrj

## What is CVE-2026-83627?

CVE-2026-83627 is a critical code injection vulnerability in wpmudev Hummingbird Performance – Cache & Page Speed Optimization for Core Web Vitals | Critical CSS | Minify CSS | Defer CSS Javascript | CDN, published on 5 Sep 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.

### Official description

The Hummingbird – Speed Optimization, Caching, Minify, Compress & CDN plugin for WordPress is vulnerable to Remote Code Execution in all versions up to, and including, 3.21.0 via the log_msg() function in core/modules/class-page-cache.php. The page-cache debug log is written to wp-content/wphb-logs/page-caching-log.php, a directly web-accessible PHP file that is supposed to be protected by a leading '<?php die(); ?>' header. That header is guarded by class_exists( 'Filesystem' ), which can never match because class_exists() resolves string arguments in the global namespace while the class is Hummingbird\Core\Filesystem; when the log is created during a front-end request the header is therefore omitted entirely. get_cookies() then writes the raw name of any cookie matching the wphb_cache_ prefix into that file without sanitization. This makes it possible for unauthenticated attackers to write arbitrary PHP into the log file with a single anonymous request and execute it by requesting the file directly, resulting in full remote code execution. Exploitation requires the site administrator to have enabled Page Caching with the Debug Log option (non-default), and the log file to be created during a front-end request — a state reached by the plugin's own 'Clear logs' action, any cache flush, or unattended via the plugin's daily log-rotation cron, which can strip the protective header from an existing log file.

Weakness: CWE-94 (Improper Control of Generation of Code)

## Which versions are affected by CVE-2026-83627?


## How do I fix CVE-2026-83627?

No fix has been published for CVE-2026-83627 yet. Limit exposure of the affected software until one is available.

## Is CVE-2026-83627 being exploited?

There is no known exploitation of CVE-2026-83627 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-83627 and fix it if it is affected.

What it is: CVE-2026-83627 is a critical code injection vulnerability in wpmudev Hummingbird Performance – Cache & Page Speed Optimization for Core Web Vitals | Critical CSS | Minify CSS | Defer CSS Javascript | CDN, published on 5 Sep 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.
Exploitation: There is no known exploitation of CVE-2026-83627 in the wild and no public exploit code.

Affected product: wpmudev Hummingbird Performance – Cache & Page Speed Optimization for Core Web Vitals | Critical CSS | Minify CSS | Defer CSS Javascript | CDN. No package-level version data is available, so check the vendor advisory linked from the reference page.

Task:
1. Search the dependency manifests and lockfiles (for example package.json, package-lock.json, requirements.txt, poetry.lock, uv.lock, pom.xml, build.gradle, go.mod, Cargo.lock, Gemfile.lock) and any Dockerfiles for the affected packages, including transitive dependencies.
2. If an affected version is in use, upgrade it to the fixed version for its release line with the project's package manager, so the lockfile is regenerated. Prefer the smallest upgrade that fixes it.
3. If there is no fix, or the upgrade would break the build, do not guess: explain the risk and the safest workaround instead.
4. Run the tests and summarise what changed and why.
5. If nothing in the project is affected, say so and change nothing.

Reference: https://insights.sbomify.com/CVE-2026-83627/ (Markdown: https://insights.sbomify.com/CVE-2026-83627/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-83627
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-83627
- OSV: https://osv.dev/vulnerability/CVE-2026-83627

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From sbomify Insights: https://insights.sbomify.com/CVE-2026-83627/
Summaries are generated and may contain mistakes; the official description above is the record.