7.5

CVSS Score

3.1

-

CVSS Score

Basic Information

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CVE-2026-35526

CVE-2026-35526: Strawberry GraphQL affected by a Denial of Service via unbounded WebSocket subscriptions

Strawberry GraphQL is a library for creating GraphQL APIs. Prior to 0.312.3, Strawberry GraphQL's WebSocket subscription handlers for both the graphql-transport-ws and legacy graphql-ws protocols allocate an asyncio.Task and associated Operation object for every incoming subscribe message without enforcing any limit on the number of active subscriptions per connection. An unauthenticated attacker can open a single WebSocket connection, send connection_init, and then flood subscribe messages with unique IDs. Each message unconditionally spawns a new asyncio.Task and async generator, causing linear memory growth and event loop saturation. This leads to server degradation or an OOM crash. This vulnerability is fixed in 0.312.3.

(GitHub Advisory)

Miggo Vulnerability Database

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CVE-2026-35526

CVE-2026-35526:

7.5

CVSS Score

3.1

-

CVSS Score

Basic Information

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Technical Details

Package Name	Ecosystem	Vulnerable Versions	First Patched Version
strawberry-graphql	pip	<= 0.312.2	0.312.3

Technical Details

Vulnerability Intelligence
Miggo AI

Root Cause Analysis

The vulnerability lies in the unbounded creation of WebSocket subscriptions, leading to a denial of service. The provided patch (0977a4e6b41b7cfe3e9d8ba84a43458a2b0c54c2) addresses this by introducing a max_subscriptions_per_connection limit. The analysis of the patch identified the two specific functions responsible for handling subscription requests for the different WebSocket protocols used by strawberry-graphql.

For the modern graphql-transport-ws protocol, the GraphQLTransportWSHandler.handle_subscribe function in strawberry/subscriptions/protocols/graphql_transport_ws/handlers.py is the vulnerable function. The patch adds a check to limit the number of concurrent operations (self.operations).
For the legacy graphql-ws protocol, the GraphQLWSHandler.handle_start function in strawberry/subscriptions/protocols/graphql_ws/handlers.py is the vulnerable function. The patch adds a similar check to limit the number of concurrent tasks (self.tasks).

These two functions are the direct entry points for the vulnerability, as they are responsible for allocating resources for each subscription request. An exploit would repeatedly call these functions, and they would therefore be prominent in any runtime profile or stack trace during such an attack.

Vulnerable functions

GraphQLTransportWSHandler.handle_subscribe

strawberry/subscriptions/protocols/graphql_transport_ws/handlers.py

This function handles 'subscribe' messages for the 'graphql-transport-ws' protocol. Prior to the patch, it did not enforce a limit on the number of active subscriptions, allowing an attacker to send a flood of 'subscribe' messages to create an unlimited number of `asyncio.Task` and `Operation` objects. This would lead to unbounded memory growth and event loop saturation, causing a denial of service.

GraphQLWSHandler.handle_start

strawberry/subscriptions/protocols/graphql_ws/handlers.py

This function handles 'start' messages for the legacy 'graphql-ws' protocol. Prior to the patch, it did not enforce a limit on the number of active subscriptions. An attacker could send a flood of 'start' messages, each creating a new `asyncio.Task`, leading to resource exhaustion and a denial of service. The same function was also vulnerable to an authentication bypass, as it didn't check if the connection was properly initialized before processing 'start' messages.

Vulnerability Intelligence
Miggo AI

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WAF Protection Rules

WAF Rule

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Reasoning

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