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CVE Record

CVE-2026-44241: Micronaut Framework: Unbounded formattersCache in TimeConverterRegistrar Allows Memory Exhaustion via Accept-Language Header

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.

HighCVSS 7.5Not KEV-listedUpdated
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Glexia's TakeAutomated analysishigh

Security readout for executives and security teams

Plain-English summary

CVE-2026-44241 is a denial-of-service issue in Micronaut Framework. A remote unauthenticated requester can send many unique Accept-Language values, causing an internal formatter cache to grow without limit until the JVM runs out of memory and crashes.

Executive priority

Treat as high priority for exposed Micronaut services because exploitation can crash applications without credentials. Remediation is straightforward where upgrades are possible.

Technical view

Micronaut core versions 4.3.0 before 4.10.22, 3.10.0 before 3.10.6, and before 3.8.14 use an unbounded ConcurrentHashMap in TimeConverterRegistrar. Cache keys combine @Format patterns with locales derived from Accept-Language. Arbitrary BCP 47 private-use locale tags can create unlimited unique keys. CVSS is 7.5, CWE-400.

Likely exposure

Internet-facing Micronaut applications on affected versions are most exposed, especially endpoints that trigger formatted date/time conversion using request locale data. Internal services can also be affected if reachable by untrusted clients.

Exploitation context

The provided sources describe unauthenticated network exploitation with low complexity and availability impact. CISA KEV is not indicated, and the bundle provides no evidence of active exploitation in the wild.

Researcher notes

The issue is resource exhaustion from unbounded cache key cardinality, not data theft or code execution. The core validation focus is version exposure and reachable code paths using TimeConverterRegistrar with locale-influenced formatting.

Mitigation direction

  • Upgrade Micronaut core to 4.10.22, 3.10.6, or 3.8.14 as applicable.
  • Review the Micronaut GitHub advisory for branch-specific upgrade guidance.
  • Prioritize public-facing services that process HTTP Accept-Language headers.
  • If immediate upgrade is not possible, consult vendor guidance for supported compensating controls.

Validation and detection

  • Inventory applications using micronaut-core and identify affected version ranges.
  • Confirm fixed versions are deployed in build files, lockfiles, and runtime artifacts.
  • Review logs and metrics for JVM heap growth or out-of-memory crashes.
  • Check whether exposed endpoints use @Format date/time conversion with locale-aware request handling.
Prepared
Confidence
high
Sources
9

Public sources used

Generated from the cited source records. This long-tail analysis has not been individually reviewed by a named human.

Potential ATT&CK relevance

Conservative CVE-to-ATT&CK context

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ATT&CK lookup starting points

Use these exact CWE pages and searches to review the Glexia ATT&CK library from this CVE's weakness and description context.

cwe · low confidence lookup

CWE-400: Exact CWE lookup

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cve · low confidence lookup

CVE-2026-44241 mapping review

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Vulnerability profileCVE Program record
Severity
High
CVSS
7.5 (3.1)
Known Exploited
No
Published

Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

Official CVE source material

CNA and ADP enrichment extracted from CVE v5

These fields come from the CVE record and ADP containers, not from Glexia's Take. They preserve time-varying source decisions such as CISA SSVC, KEV status, CVSS metrics, and provider references.

1CVSS vectors
3Timeline events
1ADP providers
8Source links

SSVC decision data

CISA-ADPCISA Coordinator
Timestamp
Version
2.0.3
Exploitation: pocAutomatable: yesTechnical Impact: partial

CVSS vector scores

1 official score

We collect every scored CVSS vector available in the official CNA and ADP containers. When more than one version is present, the table keeps the source vectors side by side instead of collapsing them into the highest score.

ScoreVersionSeverityVectorExploitImpactSource
7.5CVSS 3.1HighCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H3.93.6GitHub_M

Vulnerability scoring details

Base CVSS 3.1 score

7.5High
CVSS 3.1 vector shape for CVE-2026-44241Attack VectorAttack ComplexityPrivileges RequiredUser InteractionScopeConfidentiality ImpactIntegrity ImpactAvailability Impact

Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

Attack Vector
NetworkAdjacentLocalPhysical
Attack Complexity
LowHigh
Privileges Required
NoneLowHigh
User Interaction
NoneRequired
Scope
ChangedUnchanged
Confidentiality Impact
HighLowNone
Integrity Impact
HighLowNone
Availability Impact
HighLowNone

Vulnerability timeline

Timeline events are normalized from CVE metadata, CNA source timelines, ADP timelines, and KEV metadata when present.

  1. CVE reservedCVE Program

    The CVE ID was reserved by the assigning CNA.

  2. CVE publishedCVE Program

    The CVE record was published.

  3. CVE updatedCVE Program

    The CVE record metadata indicates this as the latest update time.

ADP provider summaries

CISA-ADPCISA ADP Vulnrichment
other:ssvc

Source materials

Affected products

Products and packages named in the record

VendorProductVersion / packageStatus
micronaut-projectsmicronaut-core>= 4.3.0, < 4.10.22, >= 3.10.0, < 3.10.6, < 3.8.14Listed
Weakness

CWE details

CWE-400

CWE links open Glexia weakness intelligence pages with official CWE context, developer remediation guidance, and related CVE mappings.

CWE-400 · source CWE mapping

Uncontrolled Resource Consumption

Uncontrolled Resource Consumption represents a recurring weakness pattern that can create exploitable paths when design, validation, or implementation controls are missing.

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