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CVE-2026-33701: OpenTelemetry: Unsafe Deserialization in RMI Instrumentation may Lead to Remote Code Execution

OpenTelemetry Java Instrumentation provides OpenTelemetry auto-instrumentation and instrumentation libraries for Java. In versions prior to 2.26.1, the RMI instrumentation registered a custom endpoint that deserialized incoming data without applying serialization filters. On JDK version 16 and earlier, an attacker with network access to a JMX or RMI port on an instrumented JVM could exploit this to potentially achieve remote code execution. All three of the following conditions must be true to exploit this vulnerability: First, OpenTelemetry Java instrumentation is attached as a Java agent (`-javaagent`) on Java 16 or earlier. Second, JMX/RMI port has been explicitly configured via `-Dcom.sun.management.jmxremote.port` and is network-reachable. Third, gadget-chain-compatible library is present on the classpath. This results in arbitrary remote code execution with the privileges of the user running the instrumented JVM. For JDK >= 17, no action is required, but upgrading is strongly encouraged. For JDK < 17, upgrade to version 2.26.1 or later. As a workaround, set the system property `-Dotel.instrumentation.rmi.enabled=false` to disable the RMI integration.

CriticalCVSS 9.3Not KEV-listedUpdated
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Glexia's TakeAutomated analysiscritical

Security readout for executives and security teams

Plain-English summary

A flaw in older OpenTelemetry Java agents can let a network attacker take control of an instrumented application. Exposure requires a legacy Java runtime, a reachable JMX/RMI management port, and a compatible library on the application classpath. Successful exploitation runs code with the application user’s privileges.

Executive priority

Treat confirmed three-condition exposure as an emergency because compromise could provide full control of the application process. Immediately inventory legacy Java services using OpenTelemetry and reachable management ports. Systems missing any prerequisite are not presently exploitable through this flaw, but vulnerable agents should still be upgraded promptly.

Technical view

Before version 2.26.1, OpenTelemetry’s RMI instrumentation registered an endpoint that deserialized untrusted data without serialization filters. On JDK 16 or earlier, a network-reachable JMX/RMI service and a compatible gadget chain can turn this CWE-502 flaw into unauthenticated remote code execution. The supplied CVSS v4.0 score is 9.3.

Likely exposure

Exposure is configuration-specific. All three conditions must coexist: the vulnerable agent runs through -javaagent on JDK 16 or earlier; an explicitly configured JMX/RMI port is network-reachable; and the runtime classpath contains a gadget-chain-compatible library. JDK 17 and later do not require action according to the advisory, although upgrading the agent remains encouraged.

Exploitation context

The source bundle marks this CVE as absent from KEV and provides no evidence of active exploitation. Nevertheless, affected services could be attacked remotely without privileges or user interaction when every prerequisite is present. Impact is complete compromise of the instrumented JVM under its operating-system account.

Researcher notes

The vulnerable boundary is OpenTelemetry’s custom RMI endpoint, not every Java RMI deployment. Version, JDK, network reachability, and classpath composition must all be validated before declaring exposure. The fix is represented by the 2.26.1 release and referenced patch commit. No exploit attempt is needed for defensive confirmation.

Mitigation direction

  • Upgrade OpenTelemetry Java Instrumentation to version 2.26.1 or later.
  • As an interim workaround, disable RMI instrumentation using the documented system property.
  • Move legacy deployments to JDK 17 or later where operationally feasible.
  • Prioritize remediation where management ports are reachable from untrusted networks.

Validation and detection

  • Inventory JVMs using the OpenTelemetry Java agent and record agent versions.
  • Identify affected deployments running JDK 16 or earlier.
  • Confirm whether a remote JMX/RMI port is explicitly configured.
  • Assess whether each configured management port is reachable from untrusted networks.
  • Review affected application classpaths for gadget-chain-compatible libraries.
  • Verify the upgraded agent or documented RMI-disable workaround is active after restart.
Prepared
Confidence
high
Sources
5

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

These mappings and lookup hints may be relevant to the vulnerability behavior, CWE, affected product, or exposure path. Glexia-inferred context is not an official MITRE, ATT&CK, CWE, or CVE Program mapping.

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 · medium confidence lookup

CWE-502: Code execution behavior lookup

Code execution and unsafe deserialization weaknesses often justify reviewing execution behavior and process telemetry. Open the exact CWE lookup page first, then review the ATT&CK searches from that MITRE weakness context. This is a Glexia lookup hint, not an official ATT&CK mapping.

Open ATT&CK lookup
description · low confidence lookup

Execution behavior lookup

The CVE wording references code or command execution, so execution technique review may help defensive triage. This is a Glexia inferred lookup path, not an official MITRE, ATT&CK, or CVE Program mapping.

Open ATT&CK lookup
cve · low confidence lookup

CVE-2026-33701 mapping review

Open the CVE-to-ATT&CK bridge for reviewed, inferred, or future official mappings tied to this CVE.

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Vulnerability profileCVE Program record
Severity
Critical
CVSS
9.3 (4.0)
Known Exploited
No
Published

Vector: CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N

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.

2CVSS vectors
5Timeline events
2ADP providers
7Source links

SSVC decision data

CISA-ADPCISA Coordinator
Timestamp
Version
2.0.3
Exploitation: noneAutomatable: yesTechnical Impact: total

CVSS vector scores

2 official scores

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
9.3CVSS 4.0CriticalCVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N——GitHub_M
8.1CVSS 3.1HighCVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:H2.25.9redhat-SADP

Vulnerability scoring details

Base CVSS 4.0 score

9.3Critical
CVSS 4.0 vector shape for CVE-2026-33701Attack VectorAttack ComplexityAttack RequirementsPrivileges RequiredUser InteractionVS ConfidentialityVS IntegrityVS AvailabilitySS ConfidentialitySS IntegritySS Availability

Vector: CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N

Attack Vector
NetworkAdjacentLocalPhysical
Attack Complexity
LowHigh
Attack Requirements
NonePresent
Privileges Required
NoneLowHigh
User Interaction
NonePassiveActive
VS Confidentiality
HighLowNone
VS Integrity
HighLowNone
VS Availability
HighLowNone
SS Confidentiality
HighLowNone
SS Integrity
HighLowNone
SS Availability
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. ADP timelineredhat-SADP

    Made public.

  3. CVE publishedCVE Program

    The CVE record was published.

  4. ADP timelineredhat-SADP

    Reported to Red Hat.

  5. CVE updatedCVE Program

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

ADP provider summaries

CISA-ADPCISA ADP Vulnrichment
other:ssvc
redhat-SADPio.opentelemetry.javaagent/opentelemetry-javaagent: OpenTelemetry Java Instrumentation: Remote code execution via deserialization vulnerability in RMI
other:Red Hat severity ratingcvssV3_1
  • 2026-03-27T01:01:57.058Z: Reported to Red Hat.
  • 2026-03-27T00:01:12.327Z: Made public.

Source materials

Affected products

Products and packages named in the record

VendorProductVersion / packageStatus
open-telemetryopentelemetry-java-instrumentation< 2.26.1Listed
Weakness

CWE details

CWE-502

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

CWE-502 · source CWE mapping

Deserialization of Untrusted Data

Deserialization of Untrusted Data represents a recurring weakness pattern that can create exploitable paths when design, validation, or implementation controls are missing.

Open CWE intelligenceSame-CWE CVEs