CVE-2024-52581

EUVD-2024-0214 · Published Nov 20, 2024

Litestar allows unbounded resource consumption (DoS vulnerability)

Summary

Litestar offers multiple methods to return a parsed representation of the request body, as well as extractors that rely on those parsers to map request content to structured data types. Multiple of those parsers do not have size limits when reading the request body into memory, which allows an attacker to cause excessive memory consumption on the server by sending large requests.

Details

The Request methods to parse json, msgpack or form-data all read the entire request stream into memory via await self.body() without a prior size check or size limit. There may be other places (e.g. extractors) where this can happen.

For most formats, a configurable size limit would be sufficient to mitigate this issue. The total request size can also be limited by a proxy (e.g. nginx) in front of the actual application as a workaround. However, for applications that actually want to accept large file uploads via multipart/form-data, a simple size limit would not be practical. The multipart parser currently used by Litestar expects a single byte string as input and does not support incremental parsing via Request.stream(). Applications could bypass the Litestar parser and use a streaming parser to read from Request.stream() instead, but that would not work with extractors and other features of the framework. Switching the parser for a different implementation is currently not possible via public APIs.

PoC

Start an applications that accesses Request.json(), Request.msgpack() or Request.form() or uses an extractor that relies on those parsers internally, and send a large request with a matching content type. The actual content of the request does not matter. For example: curl -F "foo=</dev/random" http://127.0.0.1:8000/) for multipart/form-data. Server memory consumption will increase very quickly until memory (and swap) are exhausted.

Impact

This is a denial of service (DoS) vulnerability affecting all Litestar applications that process json, msgpack or form-data submission requests.

Technologies

Litestar LitestarStarlite Starlite

Weaknesses

CWE-770

CVSS scores

v3.17.5CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

MITRE ATT&CK

Inferred

Where this vulnerability fits in an attack

ReconImpact

Initial Access Impact

T1190Exploit Public-Facing Application T1498.001Direct Network Flood T1498.002Reflection Amplification T1499Endpoint Denial of Service T1499.001OS Exhaustion Flood T1499.002Service Exhaustion Flood T1499.003Application Exhaustion Flood

References

Potentially impacted assets

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Google Brotli decoder - Remote Code Execution via compressed requests (Exploitation Check)

This control is the second step of the Patrowl response to CVE-2026-111497 (Node2Shell). It complements the first control of 22 October 2026, which focused on the Node.js runtime, and does not replace it. Why a second control CVE-2026-111497 is an out-of-bounds write in the Google Brotli decoder, the library that decompresses Brotli ("br") data. It was first published as a Node.js vulnerability, because Node.js bundles this decoder. Later publications showed that the flaw is in the library itself. Every product that embeds an affected version of the decoder is concerned, whatever its language or vendor. A public proof of concept demonstrates code execution. Any server that decompresses request bodies sent with "Content-Encoding: br" exposes the decoder to unauthenticated attackers. Known cases include Express 5 and NestJS 11 on Node.js, Koa and Fastify setups, Bun, Envoy and Istio with request decompression enabled, and any application or reverse proxy that decodes Brotli request bodies with an affected library. The flaw also works in the other direction. A malicious server can compromise an unpatched client that decodes a Brotli response, for example Node.js fetch(), Python clients (requests, httpx, aiohttp, Scrapy) with the Brotli or brotlicffi package, or libcurl builds with Brotli support. What this control checks Patrowl sends small, valid Brotli-compressed requests to each asset and observes whether the server decodes them. The check does not depend on the technology: it detects the behaviour, whatever the stack behind it. These requests are what any legitimate client could send. They never reach the vulnerable code path and cannot affect the availability of the service. How to read the result Potentially impacted means the asset decodes Brotli request bodies: the attack surface is exposed. It does not confirm that the asset is vulnerable. The version of the Brotli decoder in use is not visible from the outside. This check covers applications that parse request bodies on their root path. A Not impacted result does not rule out exposure on other routes, nor on the client side. Checking the versions on the servers remains the only exhaustive verification. Affected and fixed versions Google Brotli 1.0.3 to 1.2.0 are affected, fixed in 1.0.10, 1.1.1 and 1.2.1. Fixed releases of the main products embedding it: Node.js 22.23.4, 24.22.1 and 26.12.1 (end-of-life lines 20.x and older and 25.x receive no fix), Bun 1.4.4, Envoy 1.37.8, 1.38.6, 1.39.3 and 1.40.0, Istio 1.29.9, 1.30.6 and 1.31.2, Python Brotli 1.2.1 and brotlicffi 1.2.1.0. Products that link against the system library depend on the Brotli package of the Linux distribution. Recommendations Update every component that embeds the Brotli decoder (only real fix). Start with the assets flagged by this control. Restart the processes after the update. Rebuild containers, single-executable applications and appliances that bundle an affected runtime or library. Reduce the exposure until the update is deployed. Reject requests with "Content-Encoding: br" at the reverse proxy, load balancer or WAF, case-insensitively and including lists such as "gzip, br". On Envoy and Istio, disable request decompression for Brotli. Review outbound calls. List the features that fetch content from servers you do not control, and patch the services that host them first.