# CVE-2026-85786: Incomplete fix for CVE-2026-75936 memory-amplification denial of service in Amazon ion-java

> Remote attackers can cause denial of service in Amazon ion-java by sending crafted compressed documents that expand excessively, requiring an upgrade to fix.

- **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:** No
- **Published:** 4 Sep 2026
- **Updated:** 4 Sep 2026

## What is CVE-2026-85786?

CVE-2026-85786 is a high-severity denial of service vulnerability in Amazon ion-java, published on 4 Sep 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.

### Official description

Improper handling of highly compressed data in Amazon ion-java before 1.12.1 might allow remote attackers to cause a denial of service via a crafted compressed Ion document that expands to an arbitrarily large size upon decompression due to insufficient coverage of the GZIP auto-decompression opt-out introduced for CVE-2026-75936.

To remediate this issue, users should upgrade to version 1.12.1.

Weakness: CWE-409 (Improper Handling of Highly Compressed Data (Data Amplification))

## Which versions are affected by CVE-2026-85786?


## How do I fix CVE-2026-85786?

No fix has been published for CVE-2026-85786 yet. Limit exposure of the affected software until one is available.

## Is CVE-2026-85786 being exploited?

There is no known exploitation of CVE-2026-85786 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-85786 and fix it if it is affected.

What it is: CVE-2026-85786 is a high-severity denial of service vulnerability in Amazon ion-java, published on 4 Sep 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-2026-85786 in the wild and no public exploit code.

Affected product: Amazon ion-java. No package-level version data is available, so check the vendor advisory linked from the reference page.

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-2026-85786/ (Markdown: https://insights.sbomify.com/CVE-2026-85786/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-85786
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-85786
- OSV: https://osv.dev/vulnerability/CVE-2026-85786

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-85786/
Summaries are generated and may contain mistakes; the official description above is the record.