CVE-2026-25960

vLLM is an inference and serving engine for large language models (LLMs). The SSRF protection fix for CVE-2026-24779 add in 0.15.1 can be bypassed in the load_from_url_async method due to inconsistent URL parsing behavior between the validation layer and the actual HTTP client. The SSRF fix uses urllib3.util.parse_url() to validate and extract the hostname from user-provided URLs. However, load_from_url_async uses aiohttp for making the actual HTTP requests, and aiohttp internally uses the yarl library for URL parsing. This vulnerability in 0.17.0.

vLLM is an inference and serving engine for large language models (LLMs). The SSRF protection fix for CVE-2026-24779 add in 0.15.1 can be bypassed in the load_from_url_async method due to inconsistent URL parsing behavior between the validation layer and the actual HTTP client. The SSRF fix uses urllib3.util.parse_url() to validate and extract the hostname from user-provided URLs. However, load_from_url_async uses aiohttp for making the actual HTTP requests, and aiohttp internally uses the yarl library for URL parsing. This vulnerability in 0.17.0.

Summary

The SSRF protection fix for https://github.com/vllm-project/vllm/security/advisories/GHSA-qh4c-xf7m-gxfc can be bypassed in the load_from_url_async method due to inconsistent URL parsing behavior between the validation layer and the actual HTTP client.

Affected Component

• File: vllm/connections.py
• Function: load_from_url_async

Vulnerability Details

Root Cause

The SSRF fix uses urllib3.util.parse_url() to validate and extract the hostname from user-provided URLs. However, load_from_url_async uses aiohttp for making the actual HTTP requests, and aiohttp internally uses the yarl library for URL parsing.

These two URL parsers handle backslash characters (\) differently:

| Parser | Input URL | Parsed Host | Parsed Path | Behavior | |--------|-----------|-------------|-------------|----------| | urllib3.parse_url() | https://httpbin.org\@evil.com/ | httpbin.org | /%[email protected]/ | URL-encodes \ as %5C, treats \@evil.com/ as part of the path | | yarl (via aiohttp) | https://httpbin.org\@evil.com/ | evil.com | / | Treats \ as part of userinfo (user: httpbin.org\), the @ acts as the userinfo/host separator |

Attack Scenario

# Attacker provides this URL
malicious_url = "https://httpbin.org\\@evil.com/"

# 1. Validation layer (urllib3.parse_url)
parsed = urllib3.util.parse_url(malicious_url)
# parsed.host == "httpbin.org"  ✅ Passes validation

# 2. Actual request (aiohttp with yarl)
async with aiohttp.ClientSession() as session:
    async with session.get(malicious_url) as response:
        # Request actually goes to evil.com!  ❌ Bypass!

Why This Happens

1. yarl: Interprets httpbin.org\ as the userinfo component, and @ as the userinfo/host separator, so the URL is parsed as user=httpbin.org\, host=evil.com, path=/
2. urllib3: URL-encodes the backslash as %5C, so \@evil.com/ becomes /%[email protected]/ which is treated as part of the path, leaving host=httpbin.org

This inconsistency allows an attacker to:

• Bypass the hostname allowlist check
• Access arbitrary internal/external services
• Perform full SSRF attacks

Fixes

• https://github.com/vllm-project/vllm/pull/34743

vLLM is an inference and serving engine for large language models (LLMs). The SSRF protection fix for CVE-2026-24779 add in 0.15.1 can be bypassed in the load_from_url_async method due to inconsistent URL parsing behavior between the validation layer and the actual HTTP client. The SSRF fix uses urllib3.util.parse_url() to validate and extract the hostname from user-provided URLs. However, load_from_url_async uses aiohttp for making the actual HTTP requests, and aiohttp internally uses the yarl library for URL parsing. This vulnerability in 0.17.0.

vLLM is an inference and serving engine for large language models (LLMs). The SSRF protection fix for CVE-2026-24779 add in 0.15.1 can be bypassed in the load_from_url_async method due to inconsistent URL parsing behavior between the validation layer and the actual HTTP client. The SSRF fix uses urllib3.util.parse_url() to validate and extract the hostname from user-provided URLs. However, load_from_url_async uses aiohttp for making the actual HTTP requests, and aiohttp internally uses the yarl library for URL parsing. This vulnerability in 0.17.0.

Summary

The SSRF protection fix for https://github.com/vllm-project/vllm/security/advisories/GHSA-qh4c-xf7m-gxfc can be bypassed in the load_from_url_async method due to inconsistent URL parsing behavior between the validation layer and the actual HTTP client.

Affected Component

• File: vllm/connections.py
• Function: load_from_url_async

Vulnerability Details

Root Cause

The SSRF fix uses urllib3.util.parse_url() to validate and extract the hostname from user-provided URLs. However, load_from_url_async uses aiohttp for making the actual HTTP requests, and aiohttp internally uses the yarl library for URL parsing.

These two URL parsers handle backslash characters (\) differently:

| Parser | Input URL | Parsed Host | Parsed Path | Behavior | |--------|-----------|-------------|-------------|----------| | urllib3.parse_url() | https://httpbin.org\@evil.com/ | httpbin.org | /%[email protected]/ | URL-encodes \ as %5C, treats \@evil.com/ as part of the path | | yarl (via aiohttp) | https://httpbin.org\@evil.com/ | evil.com | / | Treats \ as part of userinfo (user: httpbin.org\), the @ acts as the userinfo/host separator |

Attack Scenario

# Attacker provides this URL
malicious_url = "https://httpbin.org\\@evil.com/"

# 1. Validation layer (urllib3.parse_url)
parsed = urllib3.util.parse_url(malicious_url)
# parsed.host == "httpbin.org"  ✅ Passes validation

# 2. Actual request (aiohttp with yarl)
async with aiohttp.ClientSession() as session:
    async with session.get(malicious_url) as response:
        # Request actually goes to evil.com!  ❌ Bypass!

Why This Happens

1. yarl: Interprets httpbin.org\ as the userinfo component, and @ as the userinfo/host separator, so the URL is parsed as user=httpbin.org\, host=evil.com, path=/
2. urllib3: URL-encodes the backslash as %5C, so \@evil.com/ becomes /%[email protected]/ which is treated as part of the path, leaving host=httpbin.org

This inconsistency allows an attacker to:

• Bypass the hostname allowlist check
• Access arbitrary internal/external services
• Perform full SSRF attacks

Fixes

• https://github.com/vllm-project/vllm/pull/34743

Summary

The SSRF protection fix for https://github.com/vllm-project/vllm/security/advisories/GHSA-qh4c-xf7m-gxfc can be bypassed in the load_from_url_async method due to inconsistent URL parsing behavior between the validation layer and the actual HTTP client.

Affected Component

• File: vllm/connections.py
• Function: load_from_url_async

Vulnerability Details

Root Cause

The SSRF fix uses urllib3.util.parse_url() to validate and extract the hostname from user-provided URLs. However, load_from_url_async uses aiohttp for making the actual HTTP requests, and aiohttp internally uses the yarl library for URL parsing.

These two URL parsers handle backslash characters (\) differently:

| Parser | Input URL | Parsed Host | Parsed Path | Behavior | |--------|-----------|-------------|-------------|----------| | urllib3.parse_url() | https://httpbin.org\@evil.com/ | httpbin.org | /%[email protected]/ | URL-encodes \ as %5C, treats \@evil.com/ as part of the path | | yarl (via aiohttp) | https://httpbin.org\@evil.com/ | evil.com | / | Treats \ as part of userinfo (user: httpbin.org\), the @ acts as the userinfo/host separator |

Attack Scenario

# Attacker provides this URL
malicious_url = "https://httpbin.org\\@evil.com/"

# 1. Validation layer (urllib3.parse_url)
parsed = urllib3.util.parse_url(malicious_url)
# parsed.host == "httpbin.org"  ✅ Passes validation

# 2. Actual request (aiohttp with yarl)
async with aiohttp.ClientSession() as session:
    async with session.get(malicious_url) as response:
        # Request actually goes to evil.com!  ❌ Bypass!

Why This Happens

1. yarl: Interprets httpbin.org\ as the userinfo component, and @ as the userinfo/host separator, so the URL is parsed as user=httpbin.org\, host=evil.com, path=/
2. urllib3: URL-encodes the backslash as %5C, so \@evil.com/ becomes /%[email protected]/ which is treated as part of the path, leaving host=httpbin.org

This inconsistency allows an attacker to:

• Bypass the hostname allowlist check
• Access arbitrary internal/external services
• Perform full SSRF attacks

Fixes

• https://github.com/vllm-project/vllm/pull/34743