# CVE-2026-77831: Algorithmic-complexity denial of service in AshPaperTrail full-diff list tracking

> An attacker can cause denial of service via excessive CPU and memory usage by submitting large array attributes to AshPaperTrail full-diff tracking.

- **Severity:** Low 2.1 (`CVSS:4.0/AV:L/AC:L/AT:P/PR:N/UI:N/VC:N/VI:N/VA:L/SC:N/SI:N/SA:N`)
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Local or same network only
- **Victim action needed:** Not needed
- **Fix available:** Yes
- **Published:** 30 Aug 2026
- **Updated:** 31 Aug 2026
- **Also known as:** EEF-CVE-2026-77831, GHSA-7c66-59m8-723c

## What is CVE-2026-77831?

CVE-2026-77831 is a low-severity denial of service vulnerability in ash-project ash_paper_trail, published on 30 Aug 2026. It can only be exploited from the same machine or local network, with no action from the victim.

### Official description

Inefficient Algorithmic Complexity vulnerability in ash-project ash_paper_trail allows a user who can submit a large array attribute to a paper-trailed create or update action to cause a denial of service through excessive CPU and memory use.

With full-diff change tracking, AshPaperTrail.ChangeBuilders.FullDiff.ListChange pairs each prior array element against the new list by rebuilding the remaining-elements accumulator with acc ++ [tuple] on every step, copying the growing list each time, so the pairing scales cubically in the array length. Nothing bounds the length and the value comes straight from action input, so one request carrying a large accepted {:array, _} attribute forces tens of seconds of CPU and multi-gigabyte allocations.

This issue affects ash_paper_trail: from 0.1.1 before 0.7.0.

Weakness: CWE-407 (Inefficient Algorithmic Complexity)

## Which versions are affected by CVE-2026-77831?

1 open source package ship an affected version, including ash_paper_trail.


| Package | Ecosystem | Affected | Fixed in |
| --- | --- | --- | --- |
| `ash_paper_trail` | Hex | From 0.1.1 | 0.7.0 |

## How do I fix CVE-2026-77831?

Upgrade ash_paper_trail to 0.7.0 or later.

## Is CVE-2026-77831 being exploited?

It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-77831 exists.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-77831 and fix it if it is affected.

What it is: CVE-2026-77831 is a low-severity denial of service vulnerability in ash-project ash_paper_trail, published on 30 Aug 2026. It can only be exploited from the same machine or local network, with no action from the victim.
Exploitation: It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-77831 exists.

Affected packages and fixed versions:
- ash_paper_trail (Hex): affected from 0.1.1; fixed in 0.7.0

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-2026-77831/ (Markdown: https://insights.sbomify.com/CVE-2026-77831/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-77831
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-77831
- OSV: https://osv.dev/vulnerability/CVE-2026-77831

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-77831/
Summaries are generated and may contain mistakes; the official description above is the record.