# CVE-2026-44242: Micronaut has Unbounded `bundleCache` in `ResourceBundleMessageSource` that Allows Memory Exhaustion via `Accept-Language` Header

> An unauthenticated attacker can exhaust heap memory and cause denial of service by sending requests with unique Accept-Language headers in applications using ResourceBundleMessageSource.

- **Severity:** Low 3.7 (`CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:L`)
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** Yes
- **Published:** 12 May 2026
- **Updated:** 13 May 2026
- **Also known as:** ECHO-78e3-aff5-2f5b, GHSA-3rfq-4wpf-qqw3

## What is CVE-2026-44242?

CVE-2026-44242 is a low-severity denial of service vulnerability in micronaut-projects micronaut-core, published on 12 May 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.

### Official description

Micronaut Framework is a JVM-based full stack Java framework designed for building modular, easily testable JVM applications. Prior to 4.10.22, the bundleCache is keyed by (Locale, baseName) where the locale originates from the HTTP Accept-Language header. In applications that explicitly register a ResourceBundleMessageSource bean and serve HTML error responses, an unauthenticated attacker can exhaust heap memory by sending requests with large numbers of unique Accept-Language values, each causing a new entry in the unbounded bundleCache. This vulnerability is fixed in 4.10.22.

Weakness: CWE-400 (Uncontrolled Resource Consumption)

## Which versions are affected by CVE-2026-44242?

6 open source packages ship an affected version, including io.micronaut:micronaut-inject.


| Package | Ecosystem | Affected | Fixed in |
| --- | --- | --- | --- |
| `io.micronaut:micronaut-inject` | Maven | All versions | 3.8.14 |
| `io.micronaut:micronaut-inject` | Maven | All versions | 3.8.14 |
| `io.micronaut:micronaut-inject` | Maven | From 3.10.0 | 3.10.6 |
| `io.micronaut:micronaut-inject` | Maven | From 3.10.0 | 3.10.6 |
| `io.micronaut:micronaut-inject` | Maven | From 4.10.0 | 4.10.22 |
| `io.micronaut:micronaut-inject` | Maven | From 4.10.0 | 4.10.22 |

## How do I fix CVE-2026-44242?

Upgrade io.micronaut:micronaut-inject to a fixed version for your release line: 3.8.14, 3.10.6 or 4.10.22.

## Is CVE-2026-44242 being exploited?

It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-44242 exists.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-44242 and fix it if it is affected.

What it is: CVE-2026-44242 is a low-severity denial of service vulnerability in micronaut-projects micronaut-core, published on 12 May 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.
Exploitation: It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-44242 exists.

Affected packages and fixed versions:
- io.micronaut:micronaut-inject (Maven): affected all versions; fixed in 3.8.14
- io.micronaut:micronaut-inject (Maven): affected all versions; fixed in 3.8.14
- io.micronaut:micronaut-inject (Maven): affected from 3.10.0; fixed in 3.10.6
- io.micronaut:micronaut-inject (Maven): affected from 3.10.0; fixed in 3.10.6
- io.micronaut:micronaut-inject (Maven): affected from 4.10.0; fixed in 4.10.22
- io.micronaut:micronaut-inject (Maven): affected from 4.10.0; fixed in 4.10.22

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-2026-44242/ (Markdown: https://insights.sbomify.com/CVE-2026-44242/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-44242
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-44242
- OSV: https://osv.dev/vulnerability/CVE-2026-44242

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From sbomify Insights: https://insights.sbomify.com/CVE-2026-44242/
Summaries are generated and may contain mistakes; the official description above is the record.