⚠ Reference material — not professional advice. Test in staging, back up first, verify against your specific version. Use your own judgment for your environment.
● High · CVSS 8.2

How to Fix CVE-2026-33013: Denial of Service in micronaut-core

Other vulnerabilities in the same area that are worth patching alongside this one:

*By Sai Kiran Pandrala*

⚡ At a glance
SeverityCVSS 8.2 - High
Actively exploited?Not currently listed in CISA KEV
Affected>= 4.0.0-M1, < 4.10.16, < 3.10.5
Fixed inversions
Type (CWE)CWE-835: Loop with Unreachable Exit Condition ('Infinite Loop')

What is CVE-2026-33013?

CVE-2026-33013 is a denial of service flaw in micronaut-core. A crafted request triggers a code path that crashes or hangs the service, taking the product offline for legitimate users. Vendor description: Micronaut Framework is a JVM-based full stack Java framework designed for building modular, easily testable JVM applications. Versions prior to both 4.10.16 and 3.10.5 do not correctly handle descending array index order during form-urlencoded body binding in theJsonBeanPropertyBinder::expandArrayToThreshold, which allows remote attackers to cause a DoS (non-terminating loop, CPU exhaustion, and OutOfMemoryError) via crafted indexed form parameters (e.g., authors[1].name followed by authors[0].name).

Why this CVE matters

Denial-of-service flaws in a network gateway or firewall have an outsize operational impact. A single packet that reboots an inline device takes down everything behind it, which is why even non-RCE bugs on these products warrant priority patching.

For deployments of micronaut-core that have been exposed to the public internet during the disclosure window, the operating assumption should be that scanning has already happened. Even where exploitation has not been publicly observed, scanning for the vulnerable fingerprint is cheap and routine. Patching closes the door; log review and credential rotation close out the rest of the response.

Am I affected?

You are affected if your installation matches any of these version ranges:

Check your installed version against the list above. If you cannot determine the version, treat the system as affected and follow the upgrade path below.

Open micronaut-core's About dialog or run the vendor-documented version-check command. Compare the result against the affected ranges in the advisory.

How to fix CVE-2026-33013

  1. Read the vendor advisory in full: https://github.com/micronaut-projects/micronaut-core/security/advisories/GHSA-43w5-mmxv-cpvh
  2. Upgrade micronaut-core to the patched build listed in the vendor advisory.
  3. Back up the configuration (and database, where applicable) before upgrading.
  4. Apply the patch in a maintenance window. For HA pairs, upgrade the standby node first, fail over, then upgrade the former primary.
  5. Restart the affected service so the patched binary loads, then verify the new version (see verification section).

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Update the micronaut-core Java dependency to 3.10.5

Vendor advisory: https://github.com/micronaut-projects/micronaut-core/security/advisories/GHSA-43w5-mmxv-cpvh


# Vendor advisory: https://github.com/micronaut-projects/micronaut-core/security/advisories/GHSA-43w5-mmxv-cpvh
# Maven: bump the dependency in pom.xml then resync.
mvn versions:set-property -Dproperty=micronaut-core.version -DnewVersion=3.10.5
mvn clean install

# Gradle: bump the version in build.gradle then refresh.
./gradlew --refresh-dependencies build

# Verify the running runtime.
java -version

# For log4j-style runtime fixes, delete vulnerable classes from the JAR and restart.
zip -q -d <app>.jar org/apache/logging/log4j/core/lookup/JndiLookup.class
systemctl restart <service>


# Vendor advisory: https://github.com/micronaut-projects/micronaut-core/security/advisories/GHSA-43w5-mmxv-cpvh
# Restart the Windows service after upgrading the JAR.
Restart-Service -Name "<service-name>"
Get-Service -Name "<service-name>"

Verify the fix landed


# Vendor advisory: https://github.com/micronaut-projects/micronaut-core/security/advisories/GHSA-43w5-mmxv-cpvh
# 1. Confirm the running version matches the fixed-in version listed above.

# 2. Re-scan with your vulnerability scanner (Nessus, Qualys, Tenable, OpenVAS).
#    The scanner should no longer flag this CVE on the patched target.

# 3. Inspect recent service / kernel logs for crash-loops or rollback events.
journalctl -u <service> --since "10 minutes ago"
dmesg --since "10 minutes ago"

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If you cannot patch immediately

Front the service with rate limiting and drop malformed packets at a load balancer or IPS. Patch to remove the underlying crash condition.

How to verify the fix worked

If your installation was internet-reachable during the disclosure window, treat log review as part of the remediation rather than an optional follow-up. Look for repeated service restarts, crash logs from the affected daemon, and core files generated around the time of any anomalous traffic. A memory-corruption flaw used for exploitation often leaves a trail of failed attempts before the successful one.

Frequently asked questions

Is CVE-2026-33013 being exploited in the wild?

Public exploitation has not been confirmed by CISA at the time of writing. Treat the patch as time-sensitive anyway; reports often lag actual abuse.

Will a WAF or IDS rule fully mitigate CVE-2026-33013?

No. Network-layer filters can reduce noise and slow opportunistic scanners, but they will not stop a determined attacker. The vendor patch is the only durable fix.

How long should I plan for the upgrade?

Typical vendor-documented upgrade windows for micronaut-core run from a few minutes to under an hour depending on cluster size. Test in a staging environment first and follow the vendor's documented HA upgrade order.

References

*This guide was assembled from the official vendor advisory, the NVD record, and the CISA KEV catalog entry on 2026-05-25. Always confirm against the vendor advisory before applying changes in production.*