# [CRIT] [GHSA / CRITICAL] CVE-2026-45034: PHPSpreadsheet has a patch bypass for CVE-2026-34084

**Source:** GitHub Security Advisories
**Published:** 2026-06-08
**Article:** https://github.com/advisories/GHSA-87m4-826x-3crx

## Threat Profile

PHPSpreadsheet has a patch bypass for CVE-2026-34084

## Summary

CVE-2026-34084 was patched by the helper `File::prohibitWrappers`. The helper calls `parse_url($filename, PHP_URL_SCHEME)` and then checks `is_string($scheme) && strlen($scheme) > 1` to reject stream wrappers such as `phar://`, `php://`, `data://` or `expect://`. The check is not equivalent to "does the path contain a wrapper". When the input has the form `phar:///path/file.phar/inner` with three or more slashes after the scheme, …

## Indicators of Compromise (high-fidelity only)

- **CVE:** `CVE-2026-45034`
- **CVE:** `CVE-2026-34084`

## MITRE ATT&CK Techniques

- **T1190** — Exploit Public-Facing Application
- **T1204.002** — User Execution: Malicious File
- **T1059** — Command and Scripting Interpreter
- **T1059.004** — Unix Shell
- **T1059.001** — PowerShell
- **T1505.003** — Web Shell
- **T1105** — Ingress Tool Transfer

## Kill chain phases observed

_(none detected from narrative keywords)_

## Recommended hunts

### PHPSpreadsheet phar:/// three-slash wrapper in HTTP request (CVE-2026-45034)

`UC_99_2` · phase: **exploit** · confidence: **High** · AI-generated for this article

**Splunk SPL (CIM):**
```spl
| tstats `summariesonly` count min(_time) as firstTime max(_time) as lastTime values(Web.url) as urls values(Web.http_user_agent) as user_agents values(Web.http_method) as methods from datamodel=Web where (Web.url="*phar://*" OR Web.url="*phar%3A%2F%2F*" OR Web.url="*phar%3a%2f%2f*") by Web.dest Web.src Web.user
| `drop_dm_object_name(Web)`
| eval bypass_attempt=if(match(urls,"(?i)phar:/{3,}") OR match(urls,"(?i)phar%3a%2f%2f%2f"),"yes","no")
| eval cve="CVE-2026-45034"
| where bypass_attempt="yes"
| `security_content_ctime(firstTime)`
| `security_content_ctime(lastTime)`
```

### Web-server process (php-fpm / apache / nginx / w3wp) spawning shell or network tooling

`UC_99_3` · phase: **exploit** · confidence: **Medium** · AI-generated for this article

**Splunk SPL (CIM):**
```spl
| tstats `summariesonly` count min(_time) as firstTime max(_time) as lastTime values(Processes.process) as cmdlines values(Processes.process_path) as paths from datamodel=Endpoint.Processes where (Processes.parent_process_name IN ("php-fpm","php-fpm.exe","php","php.exe","php-cgi.exe","apache2","httpd","httpd.exe","nginx","nginx.exe","w3wp.exe")) AND (Processes.process_name IN ("sh","bash","dash","zsh","ksh","cmd.exe","powershell.exe","pwsh.exe","curl","curl.exe","wget","wget.exe","nc","ncat","ncat.exe","socat","python","python3","python.exe","perl","ruby","certutil.exe","bitsadmin.exe")) by Processes.dest Processes.user Processes.parent_process_name Processes.process_name
| `drop_dm_object_name(Processes)`
| eval cve="CVE-2026-45034"
| `security_content_ctime(firstTime)`
| `security_content_ctime(lastTime)`
```

**Defender KQL:**
```kql
DeviceProcessEvents
| where Timestamp > ago(7d)
| where InitiatingProcessFileName in~ ("php-fpm","php-fpm.exe","php","php.exe","php-cgi.exe","apache2","httpd","httpd.exe","nginx","nginx.exe","w3wp.exe")
| where FileName in~ ("sh","bash","dash","zsh","ksh","cmd.exe","powershell.exe","pwsh.exe","curl","curl.exe","wget","wget.exe","nc","ncat","ncat.exe","socat","python","python3","python.exe","perl","ruby","certutil.exe","bitsadmin.exe")
| where AccountName != "" and AccountName !endswith "$"
| project Timestamp, DeviceName, AccountName,
          ParentImage = InitiatingProcessFolderPath,
          ParentCmd   = InitiatingProcessCommandLine,
          ChildImage  = FolderPath,
          ChildCmd    = ProcessCommandLine,
          SHA256
| order by Timestamp desc
```

### Phar archive or PHPSpreadsheet RCE marker written by web-server process

`UC_99_4` · phase: **delivery** · confidence: **Medium** · AI-generated for this article

**Splunk SPL (CIM):**
```spl
| tstats `summariesonly` count min(_time) as firstTime max(_time) as lastTime values(Filesystem.file_path) as paths values(Filesystem.process_name) as procs from datamodel=Endpoint.Filesystem where (Filesystem.file_name="*.phar" OR Filesystem.file_name="pwned_marker" OR Filesystem.file_name="exploit.phar") AND Filesystem.process_name IN ("php-fpm","php-fpm.exe","php","php.exe","apache2","httpd","httpd.exe","nginx","nginx.exe","w3wp.exe") by Filesystem.dest Filesystem.user Filesystem.file_name Filesystem.process_name
| `drop_dm_object_name(Filesystem)`
| eval cve="CVE-2026-45034"
| `security_content_ctime(firstTime)`
| `security_content_ctime(lastTime)`
```

**Defender KQL:**
```kql
DeviceFileEvents
| where Timestamp > ago(7d)
| where ActionType in ("FileCreated","FileModified","FileRenamed")
| where InitiatingProcessFileName in~ ("php-fpm","php-fpm.exe","php","php.exe","php-cgi.exe","apache2","httpd","httpd.exe","nginx","nginx.exe","w3wp.exe")
| where FileName endswith ".phar"
     or FileName =~ "pwned_marker"
     or FileName =~ "exploit.phar"
| project Timestamp, DeviceName, FileName, FolderPath, SHA256, FileSize,
          InitiatingProcessFileName, InitiatingProcessCommandLine,
          InitiatingProcessAccountName, InitiatingProcessFolderPath
| order by Timestamp desc
```

### Article-specific behavioural hunt — [GHSA / CRITICAL] CVE-2026-45034: PHPSpreadsheet has a patch bypass for CVE-2026

`UC_99_1` · phase: **exploit** · confidence: **High**

**Splunk SPL (CIM):**
```spl
``` Article-specific bespoke detection — [GHSA / CRITICAL] CVE-2026-45034: PHPSpreadsheet has a patch bypass for CVE-2026 ```
| tstats `summariesonly` count earliest(_time) AS firstTime latest(_time) AS lastTime
    from datamodel=Endpoint.Processes
    where (Processes.process_name IN ("run.sh"))
    by Processes.dest, Processes.user, Processes.process_name,
       Processes.process, Processes.parent_process_name, Processes.process_path
| `drop_dm_object_name(Processes)`
| `security_content_ctime(firstTime)`
| append [
| tstats `summariesonly` count
    from datamodel=Endpoint.Filesystem
    where Filesystem.action IN ("created","modified")
      AND (Filesystem.file_name IN ("run.sh"))
    by Filesystem.dest, Filesystem.user, Filesystem.process_name,
       Filesystem.file_path, Filesystem.file_name
| `drop_dm_object_name(Filesystem)`
]
```

**Defender KQL:**
```kql
// Article-specific bespoke detection — [GHSA / CRITICAL] CVE-2026-45034: PHPSpreadsheet has a patch bypass for CVE-2026
// Hunts the actual binaries / paths / commandline fragments named
// in the article instead of a generic technique-class template.
DeviceProcessEvents
| where Timestamp > ago(30d)
| where (FileName in~ ("run.sh"))
| project Timestamp, DeviceName, AccountName, FileName,
          FolderPath, ProcessCommandLine,
          InitiatingProcessFileName, InitiatingProcessCommandLine
| order by Timestamp desc

// File-creation events for the named binaries / paths
DeviceFileEvents
| where Timestamp > ago(30d)
| where ActionType in ("FileCreated","FileModified")
| where (FileName in~ ("run.sh"))
| project Timestamp, DeviceName, AccountName, FolderPath,
          FileName, ActionType, InitiatingProcessFileName,
          InitiatingProcessCommandLine
| order by Timestamp desc
```

### IOC-driven hunts (use shared templates)

These are standard IOC-substitution hunts — the canonical SPL and KQL live once in [`_TEMPLATES.md`](../_TEMPLATES.md), so we don't repeat the same boilerplate on every CVE / hash / network-IOC briefing.

- **Asset exposure — vulnerability matches article CVE(s)** ([template](../_TEMPLATES.md#asset-exposure)) — phase: **recon**, confidence: **High**
  - CVE(s): `CVE-2026-45034`, `CVE-2026-34084`


## Why this matters

Severity classified as **CRIT** based on: CVE present, 5 use case(s) fired, 7 technique(s) inferred. Read the full article for actor attribution, tooling details, and any defanged IOCs in the body that aren't visible in the RSS summary.