Summary
GraphQL-core has denial of service via memory leak in aborted validations
When a validation was aborted because the document contained more errors than allowed by max_errors (100 by default), validate() raised a single module-level ValidationAbortedError instance. Python appends the frames of every raise to the existing __traceback__ of an exception that is raised again, so every aborted validation extended the traceback of this shared error. That traceback kept the frames, and with them the document, the validation context and all errors of every aborted validation, alive for the lifetime of the process.
Details
Any client can trigger an aborted validation by sending a small document with more than 100 validation errors, e.g. 101 unknown fields. No authentication is required, and since validation runs before execution, depth limiters and complexity analyzers do not prevent it. Each such request permanently retained about 124 KiB on CPython 3.12, without an upper limit, so memory grew with every request until the process was restarted or killed.
GraphQL.js uses a shared error object at the same place, but JavaScript errors capture their stack trace only once when they are created, so it is not affected. GraphQL-core 3.2 creates a new error for each aborted validation and is not affected either.
Proof of concept
import gc
import tracemalloc
from graphql import build_schema, parse, validate
schema = build_schema("type Query { a: Int }")
document = parse("{ " + " ".join(f"f{i}" for i in range(101)) + " }")
tracemalloc.start()
validate(schema, document)
gc.collect()
base = tracemalloc.get_traced_memory()[0]
for _ in range(200):
validate(schema, document)
gc.collect()
print((tracemalloc.get_traced_memory()[0] - base) // 1024, "KiB")
With GraphQL-core 3.3.0 on CPython 3.12, the retained memory grows from 147 KiB after one call to about 25 MB after 200 calls. With the fix, it stays constant at about 180 KiB.
Workarounds
If you cannot upgrade, clear the traceback of the shared error after each validation:
from graphql.validation import validate as validate_document
from graphql.validation.validate import validation_aborted_error
def validate(*args, **kwargs):
try:
return validate_document(*args, **kwargs)
finally:
validation_aborted_error.__traceback__ = None
Pass this function instead of the original validate where your framework allows it.
Credits
Reported by @riodw. @Fire162 submitted a first fix in #288.
Impact
Denial of service through memory exhaustion. A few thousand small requests are enough to push a worker past a typical 256 MB or 512 MB container limit and trigger an OOM kill. No data is disclosed or modified.
Crafted input forces the application to consume excessive CPU, memory, or other resources, degrading or denying service. Typical impact: denial of service.
CVE-2026-119286 has a CVSS score of 7.5 (High). 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 (3.3.1); upgrading removes the vulnerable code path.
Affected versions
Security releases
Kodem intelligence
Severity tells you how bad this could be in the worst case. It does not tell you whether you are exposed. Exploitability and impact are functions of runtime truth: whether the vulnerable code is present, reachable, and actually executes in your application. A vulnerable package can sit in your dependency tree and never run.
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. Kodem's runtime-powered SCA identifies whether this CVE is reachable in your applications.
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Fixed in 3.3.1.
validate() now creates a new ValidationAbortedError for every aborted validation and removes its traceback and exception context before returning it, so that the returned errors do not keep the frames of the validation alive. The module-level validation_aborted_error instance, which was not exported, has been removed.
Frequently Asked Questions
- What is CVE-2026-119286? CVE-2026-119286 is a high-severity uncontrolled resource consumption vulnerability in graphql-core (pip), affecting versions >= 3.3.0a3, < 3.3.1. It is fixed in 3.3.1. Crafted input forces the application to consume excessive CPU, memory, or other resources, degrading or denying service.
- How severe is CVE-2026-119286? CVE-2026-119286 has a CVSS score of 7.5 (High). 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.
- Which versions of graphql-core are affected by CVE-2026-119286? graphql-core (pip) versions >= 3.3.0a3, < 3.3.1 is affected.
- Is there a fix for CVE-2026-119286? Yes. CVE-2026-119286 is fixed in 3.3.1. Upgrade to this version or later.
- Is CVE-2026-119286 exploitable, and should I be worried? Whether CVE-2026-119286 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
- What actually determines whether CVE-2026-119286 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.
- How do I fix CVE-2026-119286? Upgrade
graphql-coreto 3.3.1 or later.