CVE-2026-43967 Quadratic fragment-name uniqueness check causes denial of service in absinthe
An attacker can cause denial of service in applications using the Absinthe GraphQL library by submitting queries with many fragments, triggering quadratic complexity in validation.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Over the internet
- Victim action needed
- Not needed
- Fix
- Available
What is CVE-2026-43967?
CVE-2026-43967 is a high-severity denial of service vulnerability in absinthe-graphql absinthe, published on 8 May 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.
Official 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.
Weakness: CWE-407
Which versions are affected by CVE-2026-43967?
3 open source packages ship an affected version, including absinthe. It affects 1 product.
| Package | Affected | Fixed in |
|---|---|---|
absinthe Hex | From 1.2.0 | 1.10.2 |
absinthe Hex | From 1.2.0 | 1.10.2 |
absinthe Hex | From 1.2.0 | 1.10.2 |
Products include Absinthe-Graphql Absinthe.
How do I fix CVE-2026-43967?
Upgrade absinthe to 1.10.2 or later.
Upgrade, then put limits on request size, rate and nesting depth so one client cannot exhaust the service. More about Denial of service.
Is CVE-2026-43967 being exploited?
There is no known exploitation of CVE-2026-43967 in the wild and no public exploit code.
Other vulnerabilities in absinthe-graphql absinthe
Sources
Also known as EEF-CVE-2026-43967, GHSA-9mhv-8h52-q7q2.