high CVSS 7.5 EPSS 0.58%

CVE-2024-52304·Python vulnerability

aiohttp is an asynchronous HTTP client/server framework for asyncio and Python. Prior to version 3.10.11, the Python parser parses newlines in chunk extensions incorrectly which can lead to request smuggling vulnerabilities under certain conditions. If a pure Python version of aiohttp is installed (i.e. without the usual C extensions) or `AIOHTTP_NO_EXTENSIONS` is enabled, then an attacker may be able to execute a request smuggling attack to bypass certain firewalls or proxy protections. Version 3.10.11 fixes the issue.

Severity
high
Software
Python
Fixed in
3.10.11
Published

How likely is exploitation

FIRST's Exploit Prediction Scoring System puts the probability of this CVE being exploited in the next 30 days at 0.58% — higher than 43% of all published CVEs. EPSS is an independent forecast of exploitation, not a severity rating: it says nothing about how much damage a successful attack does, which is what a CVSS score measures.

Read the two together. CVE-2024-52304 scores 7.5 on CVSS, so a successful attack would be serious — but at 0.58%, almost nobody is currently attempting it. That is a different situation from a flaw under mass exploitation, and it is usually the difference between patching on your next maintenance window and patching tonight.

Affected versions

Until: 3.10.11

Fixed in: 3.10.11

How to fix this CVE

Upgrade aiohttp to version 3.10.11 or later to remediate this HTTP request smuggling vulnerability in chunk extension parsing. This vulnerability only affects installations using the pure Python parser (without C extensions), so ensure you update your Python environment and rebuild/reinstall aiohttp without the AIOHTTP_NO_EXTENSIONS flag. After updating, restart any services or applications that depend on aiohttp to ensure the patched version is in use.

sudo dnf update python3-aiohttp

Defensia detects this vulnerability

What an exploitation attempt looks like

Sample log line indicative of exploitation attempts:

POST|GET request with Transfer-Encoding: chunked header containing chunk size followed by newline characters (\r?\n) embedded within chunk extension fields, potentially followed by malformed or oversized chunk declarations

WAF mitigation (if patching is not yet possible)

Add this rule to your WAF to block exploitation attempts while you schedule the patch. 

Implement strict HTTP request validation: reject any Transfer-Encoding: chunked requests with embedded newlines in chunk extensions; enforce RFC 7230 compliance by dropping requests with malformed chunk syntax; enable backend connection pooling with request isolation to prevent cross-request smuggling.

How to check if you are affected

  1. Check installed aiohttp version: python3 -c "import aiohttp; print(aiohttp.__version__)"
  2. Verify if AIOHTTP_NO_EXTENSIONS environment variable is set: echo $AIOHTTP_NO_EXTENSIONS
  3. Search application logs for malformed chunk encoding patterns: grep -i "chunk" /var/log/application.log | grep -E '\r?\n' | head -20
  4. Confirm the fix is applied by re-running: python3 -c "import aiohttp; print(aiohttp.__version__)" and verifying version is >= 3.10.11

FAQ

What is CVE-2024-52304?

CVE-2024-52304 is a request smuggling vulnerability in aiohttp's pure Python HTTP parser that incorrectly handles newlines in chunk extensions. This allows attackers to craft malicious requests that bypass firewall and proxy protections when the C extensions are disabled.

Is CVE-2024-52304 being actively exploited?

No, this vulnerability is not currently listed on CISA's Known Exploited Vulnerabilities (KEV) catalog and no public exploits have been disclosed, though it should still be prioritized for patching.

What versions of aiohttp are affected by CVE-2024-52304?

All aiohttp versions prior to 3.10.11 are vulnerable when running with the pure Python parser enabled (either by default or via AIOHTTP_NO_EXTENSIONS environment variable).

How do I check if my server is vulnerable to CVE-2024-52304?

Run: python3 -c "import aiohttp; print(aiohttp.__version__)" and check if the version is below 3.10.11; additionally verify echo $AIOHTTP_NO_EXTENSIONS to see if the pure Python parser is explicitly enabled.

Does Defensia detect CVE-2024-52304?

Yes — Defensia's CVE advisory scanner compares installed package versions against the NVD database. If aiohttp is installed on a monitored server, CVE-2024-52304 will appear in your dashboard with remediation steps.

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References

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