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

Severity: high (CVSS 7.5 v3.1)
Exploited in the wild: not listed in CISA KEV
EPSS: 0.6% probability of exploitation in the next 30 days
Public exploit or detection template: yes
Published: 2026-05-08 · updated 2026-06-17
Weakness: CWE-407

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.

Affected products

absinthe-graphql absinthe: from 1.2.0 (excl.) before 1.10.2 — fixed in 1.10.2

How to fix

Upgrade to a fixed version: absinthe-graphql absinthe 1.10.2. Check the vendor advisory for mitigations.

References

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