CVE-2024-23829: aiohttp's HTTP parser (the python one, not llhttp) still overly lenient about separators
Summary Security-sensitive parts of the Python HTTP parser retained minor differences in allowable character sets, that must trigger error handling to robustly match frame boundaries of proxies in order to protect against injection of additional requests. Additionally, validation could trigger exceptions that were not handled consistently with processing of other malformed input.
Details These problems are rooted in pattern matching protocol elements, previously improved by PR #3235 and GHSA-gfw2-4jvh-wgfg:
1. The expression HTTP/(\d).(\d) lacked another backslash to clarify that the separator should be a literal dot, not just any Unicode code point (result: HTTP/(\d)\.(\d)).
2. The HTTP version was permitting Unicode digits, where only ASCII digits are standards-compliant.
3. Distinct regular expressions for validating HTTP Method and Header field names were used - though both should (at least) apply the common restrictions of rfc9110 token.
PoC GET / HTTP/1ö1 GET / HTTP/1.𝟙 GET/: HTTP/1.1 Content-Encoding?: chunked
Impact Primarily concerns running an aiohttp server without llhttp: 1. behind a proxy: Being more lenient than internet standards require could, depending on deployment environment, assist in request smuggling. 2. directly accessible or exposed behind proxies relaying malformed input: the unhandled exception could cause excessive resource consumption on the application server and/or its logging facilities.
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Patch: https://github.com/aio-libs/aiohttp/pull/8074/files
Other sources
aiohttp is an asynchronous HTTP client/server framework for asyncio and Python. Security-sensitive parts of the Python HTTP parser retained minor differences in allowable character sets, that must trigger error handling to robustly match frame boundaries of proxies in order to protect against injection of additional requests. Additionally, validation could trigger exceptions that were not handled consistently with processing of other malformed input. Being more lenient than internet standards require could, depending on deployment environment, assist in request smuggling. The unhandled exception could cause excessive resource consumption on the application server and/or its logging facilities. This vulnerability exists due to an incomplete fix for CVE-2023-47627. Version 3.9.2 fixes this vulnerability.
— MITRE
Affected Software
Remediation
Recommended actions to resolve this vulnerability, in priority order.
- Upgrade
Upgrade
pip/aiohttpto a version that resolves this vulnerability.Fixed in 3.9.2 - Upgrade
Upgrade
redhat/aiohttpto a version that resolves this vulnerability.Fixed in 3.9.2 - Upgrade
Upgrade
aiohttpto a version that resolves this vulnerability.Fixed in 3.9.2Patch GHSA-8qpw-xqxj-h4r2 - Upgrade
Upgrade
aiohttpto a version that resolves this vulnerability.Patch CVE-2023-47627 - Compensating control
If deploying an aiohttp server without llhttp, validate and ensure the server HTTP parsing is robust against request smuggling as described in GHSA-8qpw-xqxj-h4r2 (i.e., apply the fix rather than relying on the parser being correct under proxy frame-boundary conditions).
Event History
Frequently Asked Questions
What is the severity of CVE-2024-23829?
CVE-2024-23829 is considered a moderate severity vulnerability that can lead to request injection issues.
How do I fix CVE-2024-23829?
To fix CVE-2024-23829, update the aiohttp package to version 3.9.2 or higher.
Which versions of aiohttp are affected by CVE-2024-23829?
CVE-2024-23829 affects aiohttp versions prior to 3.9.2.
What kind of vulnerabilities does CVE-2024-23829 expose?
CVE-2024-23829 exposes a risk of injection of additional requests due to improper character set handling.
Is CVE-2024-23829 specific to certain operating systems?
CVE-2024-23829 impacts aiohttp on multiple operating systems, including Fedora 39.