Detection: PHP Session Upload Progress with PHP Code in Upload Filename

Created: 2026-10-22 Last Updated: 2026-10-28 ID: e50cc2d0-7c71-4a2f-83dc-5ee6d4bb76a7 Author: Raven Tait, Onur Mustafa Erdogan, Nasreddine Bencherchali, Splunk Type: Anomaly Product: Splunk Enterprise Security

Description

This analytic detects multipart POST requests containing a PHPSESSID form field and an uploaded filename with a PHP opening tag. When observed with "PHP_SESSION_UPLOAD_PROGRESS" behavior, this may indicate an attempt to place executable PHP content into session-related data as part of PHP2Shell exploitation.

Search

 1`zeek_http`
 2method="POST"
 3request_headers="*"
 4
 5
 6| eval src=coalesce(src, src_ip, 'id.orig_h'),
 7       dest=coalesce(dest, dest_ip, 'id.resp_h'),
 8       dest_port=coalesce(dest_port, 'id.resp_p')
 9
10
11| eval has_phpsessid_field=if(match(request_headers, "(?im)\s*form-data;[^\\r\\n]*\\bname\\s*=\\s*\\\"?PHPSESSID\\\"?(?:;
12|[\\r\\n]
13|$)"), 1, 0)
14
15
16| rex max_match=0 field=request_headers "(?im)\s*form-data;(?<part_disposition>[^\\r\\n]*)"
17
18
19| eval php_open_tag_filenames=mvfilter(match(part_disposition, "(?i)\\bfilename\\s*=.*(?:<\\?php\\b
20|<\\?=)"))
21
22
23| where has_phpsessid_field=1 AND mvcount(php_open_tag_filenames)>0
24
25
26| stats count min(_time) as firstTime
27              max(_time) as lastTime
28              values(status_code) as status_code
29              values(user_agent) as user_agent
30              values(php_open_tag_filenames) as php_open_tag_filenames
31
32  by src dest dest_port uri
33
34
35| `security_content_ctime(firstTime)`
36
37| `security_content_ctime(lastTime)`
38
39| `php_session_upload_progress_with_php_code_in_upload_filename_filter`

Data Source

Name	Platform	Sourcetype	Source
Zeek HTTP	Web	`'zeek:http'`	`'http.log'`

Macros Used

Name	Value
security_content_ctime	`convert timeformat="%Y-%m-%dT%H:%M:%S" ctime($field$)`
php_session_upload_progress_with_php_code_in_upload_filename_filter	`search *`

php_session_upload_progress_with_php_code_in_upload_filename_filter is an empty macro by default. It allows the user to filter out any results (false positives) without editing the SPL.

Annotations

- MITRE ATT&CK

+ Kill Chain Phases

+ NIST

+ CIS

- Threat Actors

ID	Technique	Tactic
T1190	Exploit Public-Facing Application	Initial Access

Delivery

DE.AE

CIS 13

CVE

Default Configuration

This detection is configured by default in Splunk Enterprise Security to run with the following settings:

Setting	Value
Disabled	true
Cron Schedule	`0 * * * *`
Earliest Time	`-70m@m`
Latest Time	`-10m@m`
Schedule Window	`auto`
Creates Finding (Notable)	No
Creates Intermediate Finding (Risk Event)	Yes

Anomaly detections generate Intermediate Findings (Risk Events). They do not generate a Finding (Notable) directly.

Implementation

Ingest Zeek http.log with the TA for Zeek (https://splunkbase.splunk.com/app/5466), then set the zeek_http macro to select that data (the search expects sourcetype zeek:http by default). Standard Zeek HTTP logs do not include full multipart request headers. Enable a Zeek HTTP header logging script or package that captures client header names and values, and map them into request_headers. Each POST record must include the Content-Disposition lines so the search can see name="PHPSESSID" and an upload filename containing <?php or <?=.

Known False Positives

Security testing tools or development environments may upload files with PHP code in the filename. Review the request headers, destination application, and any follow-on requests or server-side execution evidence.

Associated Analytic Story

PHP2Shell

Intermediate Findings

Message	Entity Field	Entity Type	Risk Score
A multipart POST request from [$src$] to [$dest$] included a PHPSESSID form field and a PHP opening tag in an upload filename.	dest	system	40

Threat Objects

Field	Type
src	ip_address
php_open_tag_filenames	file_name

References

Detection Testing

Test Type	Status	Dataset	Source	Sourcetype
Validation	✅ Passing	N/A	N/A	N/A
Unit	✅ Passing	Dataset	`http.log`	`zeek:http`
Integration	✅ Passing	Dataset	`http.log`	`zeek:http`

Replay any dataset to Splunk Enterprise by using our replay.py tool or the UI. Alternatively you can replay a dataset into a Splunk Attack Range

Source: GitHub |

Version: 1