VulnerabilityPublished 2 Jan 2026

CVE-2026-21452: msgpack-java · Uncontrolled Resource Consumption

Affects msgpack-javaSource CVE Database V5

Not known to be exploited · CVSS 7.5 High : upgrade to 0.9.11 soon.

Data as of 26 Oct 2026, 15:59 UTC

CVSS 3.1 base score

7.5High

How severe the flaw is on the 0–10 CVSS scale.

EPSS: 0.6% chance of exploitation in 30 days – higher than 48% of CVEsExploit Prediction Scoring System: the likelihood attackers will use this flaw soon.
Patch: Available – fixed in 0.9.11

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

Attack Vector: Network
Attack Complexity: Low
Privileges Required: None
User Interaction: None
Scope: Unchanged
Confidentiality: None
Integrity: None
Availability: High

Bold values are the worst case: easiest to exploit or largest impact.

Attack Vector: Network: The vulnerable component is bound to the network stack and the set of possible attackers extends beyond the other options listed, up to and including the entire Internet. Such a vulnerability is often termed 'remotely exploitable' and can be thought of as an attack being exploitable at the protocol level one or more network hops away (e.g., across one or more routers).
Attack Complexity: Low: Specialized access conditions or extenuating circumstances do not exist. An attacker can expect repeatable success against the vulnerable component.
Privileges Required: None: The attacker is unauthorized prior to attack, and therefore does not require any access to settings or files to carry out an attack.
User Interaction: None: The vulnerable system can be exploited without any interaction from any user.
Scope: Unchanged: An exploited vulnerability can only affect resources managed by the same security authority. In this case, the vulnerable component and the impacted component are either the same, or both are managed by the same security authority.
Confidentiality: None: There is no loss of confidentiality within the impacted component.
Integrity: None: There is no loss of integrity within the impacted component.
Availability: High: There is total loss of availability, resulting in the attacker being able to fully deny access to resources in the impacted component; this loss is either sustained (while the attacker continues to deliver the attack) or persistent (the condition persists even after the attack has completed). Alternatively, the attacker has the ability to deny some availability, but the loss of availability presents a direct, serious consequence to the impacted component (e.g., the attacker cannot disrupt existing connections, but can prevent new connections; the attacker can repeatedly exploit a vulnerability that, in each instance of a successful attack, leaks a only small amount of memory, but after repeated exploitation causes a service to become completely unavailable).

Definitions: FIRST CVSS v3.1 specification.

Exploitation evidence

Disclosed: evidence found.
CVE published 2 Jan 2026
Detectable: no evidence on record.
No public nuclei template indexed
Weaponised: no evidence on record.
No public exploit code indexed in Metasploit or Exploit-DB
Exploited in the wildExploited: no evidence on record.
Not in CISA KEV and no source reports exploitation
Observed by OffSeq MirageSeen by Mirage: no evidence on record.
No attack traffic recorded by OffSeq Mirage sensors

A missing step is not evidence of safety. Sources: cve.org (opens in a new tab), the Metasploit, Exploit-DB and nuclei-templates index as of 26 Oct 2026.

Disclosed: The CVE record is public on cve.org. Its publication is t = 0.
Detectable: A public nuclei template can find exposed instances, for defenders and attackers alike.
Weaponised: Public exploit code exists in Metasploit or Exploit-DB, or CISA SSVC or the CVSS exploit maturity reports a public proof of concept.
Exploited in the wild: CISA KEV lists it, CISA SSVC rates exploitation active, or a source reports attacks.
Observed by OffSeq Mirage: OffSeq Mirage honeypot sensors recorded attack traffic for this CVE, or found exposed hosts without attack traffic.

Moments are spaced evenly, not to scale; a dashed line marks a gap of six months or more. Deltas count from t = 0. Sources that give only a date (CISA KEV, Exploit-DB, or a time of exactly 00:00Z) read “same day” rather than hours. Metasploit modules carry the flaw’s disclosure date, not their release date, and nuclei templates carry no date, so both appear above but not on the timeline.

What to do

Upgrade msgpack-java and org.msgpack/msgpack-core to 0.9.11.

Affected software

Product	Affected	Fixed in
msgpackmsgpack-java	Affected <0.9.11	Fixed in 0.9.11
Mavenorg.msgpack/msgpack-core`pkg:maven/org.msgpack/msgpack-core`Other threats	Affected <0.9.11	Fixed in 0.9.11

Check your own hosts for these packages with threat-finder (opens in a new tab), our free open-source scanner.

AI-suggested

European organizations should immediately upgrade all msgpack-java dependencies to version 0.9.11 or later to eliminate this vulnerability. Additionally, implement strict input validation and filtering on all .msgpack files, especially those sourced externally or from untrusted origins. Employ runtime monitoring and JVM heap usage alerts to detect abnormal memory consumption patterns indicative of exploitation attempts. Integrate security scanning tools capable of analyzing .msgpack files for anomalous EXT32 payload lengths. Restrict network access and authentication for services that accept or fetch .msgpack artifacts to reduce exposure. Where feasible, sandbox or isolate deserialization processes to limit the impact of potential crashes. Finally, update incident response plans to include detection and mitigation steps for deserialization-based denial-of-service attacks.

Description

CVE-2026-21452 is a high-severity denial-of-service vulnerability in msgpack-java versions prior to 0.9.11. It arises from uncontrolled resource consumption during deserialization of maliciously crafted . msgpack files containing EXT32 objects with attacker-controlled payload lengths. The vulnerability allows remote attackers to cause JVM heap exhaustion and service crashes without requiring authentication or user interaction. This can disrupt applications that deserialize untrusted . msgpack files, such as model registries, inference services, and CI/CD pipelines. The exploit involves a small but valid . msgpack file that bypasses basic validation and triggers unbounded memory allocation.

Impact

For European organizations, this vulnerability poses a significant risk to the availability of services that rely on msgpack-java for deserializing .msgpack files, particularly in AI/ML model management, cloud services, and automated deployment pipelines. Exploitation can lead to JVM crashes and service outages, potentially causing cascading failures in production environments. This can disrupt critical business operations, degrade customer experience, and incur financial losses. Organizations using vulnerable versions in cloud-hosted or on-premises inference services may face remote denial-of-service attacks without warning. The small size and validity of the malicious payload complicate detection and prevention, increasing the likelihood of successful exploitation. Given the growing adoption of AI/ML workflows and cloud-native architectures in Europe, the impact could be widespread, especially in sectors like finance, healthcare, and manufacturing that depend on continuous service availability and model inference.

CWE-400Uncontrolled Resource Consumption (opens in a new tab)
Class weaknessLikelihood of exploit: High
The product does not properly control the allocation and maintenance of a limited resource.
MITRE discourages mapping vulnerabilities to this broad entry; the root cause is usually a more specific weakness.
Architecture and Design
Design throttling mechanisms into the system architecture. The best protection is to limit the amount of resources that an unauthorized user can cause to be expended. A strong authentication and access control model will help prevent such attacks from occurring in the first place.
Architecture and Design
Mitigation of resource exhaustion attacks requires that the target system either: recognizes the attack and denies that user further access for a given amount of time, or; uniformly throttles all requests in order to make it more difficult to consume resources more quickly than they can again be freed.
Architecture and Design
Ensure that protocols have specific limits of scale placed on them.
OWASP Cheat Sheets
File Upload (opens in a new tab)
OWASP ASVS 4.0.3
V12.1.1 (opens in a new tab)
Attack patterns
XML Ping of the Death (opens in a new tab)
Regular Expression Exponential Blowup (opens in a new tab)
Sustained Client Engagement (opens in a new tab)
From MITRE CWE, MITRE CAPEC and OWASP (Top 10, OpenCRE).
CWE-789Memory Allocation with Excessive Size Value (opens in a new tab)
Variant weakness
The product allocates memory based on an untrusted, large size value, but it does not ensure that the size is within expected limits, allowing arbitrary amounts of memory to be allocated.
Implementation · Architecture and Design
Perform adequate input validation against any value that influences the amount of memory that is allocated. Define an appropriate strategy for handling requests that exceed the limit, and consider supporting a configuration option so that the administrator can extend the amount of memory to be used if necessary.
Operation
Run your program using system-provided resource limits for memory. This might still cause the program to crash or exit, but the impact to the rest of the system will be minimized.
OWASP Cheat Sheets
Abuse Case (opens in a new tab)
OWASP ASVS 4.0.3
V8.1.4 (opens in a new tab)
V13.4.1 (opens in a new tab)
V11.1.4 (opens in a new tab)
From MITRE CWE, MITRE CAPEC and OWASP (Top 10, OpenCRE).

References

Community reviews

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Exploitation evidence

What to do

Affected software

Description

AI analysisMachine-generated, updated 9 Jan 2026, 21:24 UTC

WeaknessesCWE-400, CWE-789

Technical details

References

Community reviews

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