CVE-2025-59152

While testing Litestar's RateLimitMiddleware, I discovered that rate limits can be completely bypassed by manipulating the X-Forwarded-For header. This renders IP-based rate limiting ineffective against determined attackers.

The Problem

Litestar's RateLimitMiddleware uses cache_key_from_request() to generate cache keys for rate limiting. When an X-Forwarded-For header is present, the middleware trusts it unconditionally and uses its value as part of the client identifier.

Since clients can set arbitrary X-Forwarded-For values, each different spoofed IP creates a separate rate limit bucket. An attacker can rotate through different header values to avoid hitting any single bucket's limit.

Looking at the relevant code in litestar/middleware/rate_limit.py around line 127, there's no validation of proxy headers or configuration for trusted proxies.

Reproduction Steps

Here's a minimal test case

from litestar import Litestar, get
from litestar.middleware.rate_limit import RateLimitConfig
import uvicorn

@get("/api/data")
def get_data() -> dict:
    return {"message": "sensitive data"}

rate_config = RateLimitConfig(rate_limit=("minute", 2))

app = Litestar(
    route_handlers=[get_data],
    middleware=[rate_config.middleware]
)

if __name__ == "__main__":
    uvicorn.run(app, host="0.0.0.0", port=8000)

Testing the bypass

# Normal requests get rate limited after 2 requests
curl http://localhost:8000/api/data  # 200 OK
curl http://localhost:8000/api/data  # 200 OK  
curl http://localhost:8000/api/data  # 429 Too Many Requests

# But spoofing X-Forwarded-For bypasses the limit entirely
curl -H "X-Forwarded-For: 192.168.1.100" http://localhost:8000/api/data  # 200 OK
curl -H "X-Forwarded-For: 192.168.1.101" http://localhost:8000/api/data  # 200 OK
curl -H "X-Forwarded-For: 192.168.1.102" http://localhost:8000/api/data  # 200 OK

Security Impact

This vulnerability has several concerning implications:

Brute Force Protection Bypass: Authentication endpoints protected by rate limiting become vulnerable to credential stuffing attacks. An attacker can attempt thousands of login combinations from a single source.

API Abuse: Public APIs relying on rate limiting for abuse prevention can be scraped or hammered without restriction.

Resource Exhaustion: While not a traditional DoS, the ability to bypass rate limits means attackers can consume more server resources than intended.

The issue is particularly problematic because many developers deploy Litestar applications directly (not behind a proxy) during development or in containerized environments, making this attack vector accessible.

Potential Solutions

After reviewing how other frameworks handle this:

• Default to socket IP only: Don't trust proxy headers unless explicitly configured
• Trusted proxy configuration: Add settings to specify which proxy IPs are allowed to set forwarded headers
• Header validation: Implement basic validation of forwarded IP formats

Django handles this through SECURE_PROXY_SSL_HEADER and trusted proxy lists. Express.js has similar trusted proxy configurations.

For immediate mitigation, applications can deploy behind a properly configured reverse proxy that strips/overwrites client-controllable headers before they reach Litestar.

Environment Details

• Litestar version: 2.17.0
• Python: 3.11

This affects any Litestar application using RateLimitMiddleware with default settings, which likely includes most applications that implement rate limiting.

CVE-2025-59152 has a CVSS score of 7.5 (High). The vector is network-reachable, no privileges required, and no user interaction. A CVSS score reflects the worst-case severity of the vulnerability, not your specific exposure. Whether this affects your application depends on whether the vulnerable code is present and reachable in your environment. A fixed version is available (2.18.0); upgrading removes the vulnerable code path.

Kodem intelligence

1. What is CVE-2025-59152? CVE-2025-59152 is a high-severity security vulnerability in litestar (pip), affecting versions = 2.17.0. It is fixed in 2.18.0.
2. How severe is CVE-2025-59152? CVE-2025-59152 has a CVSS score of 7.5 (High). This score reflects the worst-case severity of the vulnerability, not your specific exposure. Whether it represents real risk in your environment depends on whether the vulnerable code is present and reachable.
3. Which versions of litestar are affected by CVE-2025-59152? litestar (pip) versions = 2.17.0 is affected.
4. Is there a fix for CVE-2025-59152? Yes. CVE-2025-59152 is fixed in 2.18.0. Upgrade to this version or later.
5. Is CVE-2025-59152 exploitable, and should I be worried? Whether CVE-2025-59152 is exploitable in your environment depends on whether the vulnerable code is present and reachable. A CVSS score is a worst-case rating; it does not account for your specific deployment, configuration, or usage patterns. Kodem, an Intelligent Application Security platform, uses runtime intelligence to show which vulnerabilities actually execute in production, so you can focus on the ones that represent real risk. Get a demo
6. What actually determines whether CVE-2025-59152 is exploitable, and how bad it is? Exploitability and impact are not fixed properties of a CVE. They depend on runtime truth: whether the vulnerable code is present, reachable, and actually executes in your application. A high CVSS score on a dependency that never runs is not the same as real risk. Kodem, an Intelligent Application Security platform, uses runtime intelligence to reveal which vulnerabilities actually execute in production, so teams prioritize the ones that genuinely matter.
7. How do I fix CVE-2025-59152? Upgrade litestar to 2.18.0 or later.