# CVE-2026-44241: Micronaut has unbounded `formattersCache` in `TimeConverterRegistrar` that Allows Memory Exhaustion via `Accept-Language` Header

> An unauthenticated attacker can exhaust JVM heap memory by sending requests with unique Accept-Language headers, causing a denial of service.

- **Severity:** High 7.5 (`CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H`)
- **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:** 10 Jul 2026
- **Also known as:** CLEANSTART-2026-VZ67259, ECHO-7c8b-c5a6-558d, GHSA-8hjv-92q9-g4xj

## What is CVE-2026-44241?

CVE-2026-44241 is a high-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. From 4.3.0 to before 4.10.22, 3.10.6, and 3.8.14, TimeConverterRegistrar caches DateTimeFormatter instances in an unbounded ConcurrentHashMap<String, DateTimeFormatter> whose key is derived from the @Format annotation pattern concatenated with the locale from the HTTP Accept-Language header. Because Locale.forLanguageTag() accepts arbitrary BCP 47 private-use extensions (en-x-a001, en-x-a002, …), an unauthenticated attacker can generate an unlimited number of unique cache keys by sending requests with novel locale tags, growing the cache until heap memory is exhausted and the JVM crashes. This vulnerability is fixed in 4.10.22, 3.10.6, and 3.8.14.

Weakness: CWE-400 (Uncontrolled Resource Consumption)

## Which versions are affected by CVE-2026-44241?

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


| Package | Ecosystem | Affected | Fixed in |
| --- | --- | --- | --- |
| `io.micronaut:micronaut-context` | Maven | All versions | 3.8.14 |
| `io.micronaut:micronaut-context` | Maven | All versions | 3.8.14 |
| `io.micronaut:micronaut-context` | Maven | From 3.10.0 | 3.10.6 |
| `io.micronaut:micronaut-context` | Maven | From 3.10.0 | 3.10.6 |
| `io.micronaut:micronaut-context` | Maven | From 4.3.0 | 4.10.22 |
| `io.micronaut:micronaut-context` | Maven | From 4.3.0 | 4.10.22 |

## How do I fix CVE-2026-44241?

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

## Is CVE-2026-44241 being exploited?

It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-44241 exists.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-44241 and fix it if it is affected.

What it is: CVE-2026-44241 is a high-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-2026-44241 exists.

Affected packages and fixed versions:
- io.micronaut:micronaut-context (Maven): affected all versions; fixed in 3.8.14
- io.micronaut:micronaut-context (Maven): affected all versions; fixed in 3.8.14
- io.micronaut:micronaut-context (Maven): affected from 3.10.0; fixed in 3.10.6
- io.micronaut:micronaut-context (Maven): affected from 3.10.0; fixed in 3.10.6
- io.micronaut:micronaut-context (Maven): affected from 4.3.0; fixed in 4.10.22
- io.micronaut:micronaut-context (Maven): affected from 4.3.0; 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-2026-44241/ (Markdown: https://insights.sbomify.com/CVE-2026-44241/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-44241
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-44241
- OSV: https://osv.dev/vulnerability/CVE-2026-44241

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From sbomify Insights: https://insights.sbomify.com/CVE-2026-44241/
Summaries are generated and may contain mistakes; the official description above is the record.