CVE-2026-44241

Micronaut has unbounded formattersCache in TimeConverterRegistrar that Allows Memory Exhaustion via Accept-Language Header

• An unauthenticated attacker can crash any Micronaut server that exposes at least one endpoint with a @Format-annotated temporal type parameter, a documented, first-class framework feature.
• Memory grows linearly with the number of unique Accept-Language values sent. The BCP 47 private-use namespace (en-x-ANYTHING) provides millions of distinct valid locale strings.
• No credentials, special permissions, or exploitation of application logic are required, only the ability to send HTTP requests with custom headers.
• TimeConverterRegistrar is active in all Micronaut HTTP server applications by default; no special configuration is needed to be vulnerable.

Crafted input forces the application to consume excessive CPU, memory, or other resources, degrading or denying service. Typical impact: denial of service.

CVE-2026-44241 has a CVSS score of 7.5 (High). The vector is network-reachable, no privileges required, and no user interaction. A CVSS score reflects the worst-case severity of the vulnerability, not your specific exposure. Whether this affects your application depends on whether the vulnerable code is present and reachable in your environment. A fixed version is available (4.10.22); upgrading removes the vulnerable code path.

Kodem intelligence

Apply the same fix pattern used for GHSA-2hcp-gjrf-7fhc: replace the unbounded ConcurrentHashMap with a bounded ConcurrentLinkedHashMap:

// In TimeConverterRegistrar.java, replace line 123
import io.micronaut.core.util.clhm.ConcurrentLinkedHashMap;

private static final int MAX_FORMATTERS_CACHE_SIZE = 100;

private final Map<String, DateTimeFormatter> formattersCache =
    new ConcurrentLinkedHashMap.Builder<String, DateTimeFormatter>()
        .maximumWeightedCapacity(MAX_FORMATTERS_CACHE_SIZE)
        .build();

Alternatively, since @Format pattern values come from static annotations (a bounded, compile-time set), the locale should be excluded from the cache key and applied at use-time instead:

// In getFormatter(), cache only by pattern, apply locale at use-time
private DateTimeFormatter getFormatter(String pattern, ConversionContext context) {
    DateTimeFormatter base = formattersCache.computeIfAbsent(
        pattern, p -> DateTimeFormatter.ofPattern(p)
    );
    Locale locale = context.getLocale();
    return locale != null ? base.withLocale(locale) : base;
}

This second approach bounds the cache by the number of distinct @Format patterns in the application, which is always small and finite, fully eliminating the attack surface.

1. What is CVE-2026-44241? CVE-2026-44241 is a high-severity uncontrolled resource consumption vulnerability in io.micronaut:micronaut-context (maven), affecting versions >= 4.3.0, < 4.10.22. It is fixed in 4.10.22. Crafted input forces the application to consume excessive CPU, memory, or other resources, degrading or denying service.
2. How severe is CVE-2026-44241? CVE-2026-44241 has a CVSS score of 7.5 (High). This score reflects the worst-case severity of the vulnerability, not your specific exposure. Whether it represents real risk in your environment depends on whether the vulnerable code is present and reachable.
3. Which versions of io.micronaut:micronaut-context are affected by CVE-2026-44241? io.micronaut:micronaut-context (maven) versions >= 4.3.0, < 4.10.22 is affected.
4. Is there a fix for CVE-2026-44241? Yes. CVE-2026-44241 is fixed in 4.10.22. Upgrade to this version or later.
5. Is CVE-2026-44241 exploitable, and should I be worried? Whether CVE-2026-44241 is exploitable in your environment depends on whether the vulnerable code is present and reachable. A CVSS score is a worst-case rating; it does not account for your specific deployment, configuration, or usage patterns. Kodem, an Intelligent Application Security platform, uses runtime intelligence to show which vulnerabilities actually execute in production, so you can focus on the ones that represent real risk. Get a demo
6. What actually determines whether CVE-2026-44241 is exploitable, and how bad it is? Exploitability and impact are not fixed properties of a CVE. They depend on runtime truth: whether the vulnerable code is present, reachable, and actually executes in your application. A high CVSS score on a dependency that never runs is not the same as real risk. Kodem, an Intelligent Application Security platform, uses runtime intelligence to reveal which vulnerabilities actually execute in production, so teams prioritize the ones that genuinely matter.
7. How do I fix CVE-2026-44241? Upgrade io.micronaut:micronaut-context to 4.10.22 or later.