# 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.

- **Severity:** High 8.7 (`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`)
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** Yes
- **Published:** 8 May 2026
- **Updated:** 9 May 2026
- **Also known as:** EEF-CVE-2026-43967, GHSA-9mhv-8h52-q7q2

## 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 (Inefficient Algorithmic Complexity)

## Which versions are affected by CVE-2026-43967?

3 open source packages ship an affected version, including absinthe. It affects 1 product.


| Package | Ecosystem | 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: Absinthe-Graphql Absinthe.

## How do I fix CVE-2026-43967?

Upgrade absinthe to 1.10.2 or later.

## 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

- [CVE-2026-42793](https://insights.sbomify.com/CVE-2026-42793/): Atom table exhaustion via attacker-controlled GraphQL SDL names in absinthe (high 8.2)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-43967 and fix it if it is affected.

What it is: 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.
Exploitation: There is no known exploitation of CVE-2026-43967 in the wild and no public exploit code.

Affected packages and fixed versions:
- absinthe (Hex): affected from 1.2.0; fixed in 1.10.2
- absinthe (Hex): affected from 1.2.0; fixed in 1.10.2
- absinthe (Hex): affected from 1.2.0; fixed in 1.10.2

Task:
1. Search the dependency manifests and lockfiles (for example package.json, package-lock.json, requirements.txt, poetry.lock, uv.lock, pom.xml, build.gradle, go.mod, Cargo.lock, Gemfile.lock) and any Dockerfiles for the affected packages, including transitive dependencies.
2. If an affected version is in use, upgrade it to the fixed version for its release line with the project's package manager, so the lockfile is regenerated. Prefer the smallest upgrade that fixes it.
3. If there is no fix, or the upgrade would break the build, do not guess: explain the risk and the safest workaround instead.
4. Run the tests and summarise what changed and why.
5. If nothing in the project is affected, say so and change nothing.

Reference: https://insights.sbomify.com/CVE-2026-43967/ (Markdown: https://insights.sbomify.com/CVE-2026-43967/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-43967
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-43967
- OSV: https://osv.dev/vulnerability/CVE-2026-43967

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-43967/
Summaries are generated and may contain mistakes; the official description above is the record.