CVE-2026-41433

A flaw in the Java agent injection path allows a local attacker controlling a Java workload to overwrite arbitrary host files when Java injection is enabled and OBI is running with elevated privileges. The injector trusted TMPDIR from the target process and used unsafe file creation semantics, enabling both filesystem boundary escape and symlink-based file clobbering.

Details

The issue is in the Java agent staging logic in pkg/internal/java/java_inject.go.

The injector reads TMPDIR from the target process environment in findTempDir(...) and validates it with dirOK(...). In the vulnerable implementation, dirOK(...) used filepath.Join(root, dir), where root is /proc/<pid>/root. If dir is an absolute path, filepath.Join discards root, so values such as /etc or /proc/1/root/etc are resolved on the host instead of within the target process root.

That validated value is later reused in copyAgent(...) to build the destination path for the Java agent JAR. As a result, a malicious process can influence the privileged injector to write outside the intended /proc/<pid>/root boundary.

The file creation step further increases impact. The vulnerable code created the destination with os.OpenFile(..., os.O_WRONLY|os.O_CREATE|os.O_TRUNC, 0o644). Because this does not use exclusive creation or symlink protections, an attacker can pre-create a symlink at the chosen destination, for example in a writable temp directory, and cause the injector to truncate or overwrite another file writable by the privileged OBI process.

Relevant code paths:

• pkg/internal/java/java_inject.go: findTempDir(...)
• pkg/internal/java/java_inject.go: dirOK(...)
• pkg/internal/java/java_inject.go: copyAgent(...)

In short, the vulnerability is caused by two issues acting together:

1. Untrusted TMPDIR from the target process can escape the intended target root.
2. The destination JAR is written with unsafe open semantics that allow clobbering via symlink or attacker-controlled destination selection.

PoC

Prerequisites:

• OBI is running with elevated privileges on the host.
• Java injection is enabled.
• The attacker can run or control a Java process on the same host.

Reproduction outline for the path escape case:

1. Start a Java process with a controlled environment variable such as:
   • TMPDIR=/etc
   • or TMPDIR=/proc/1/root/etc
2. Ensure the process is discovered by OBI and selected for Java agent injection.
3. Wait for the injector to stage the agent JAR.
4. Observe that the injector attempts to write obi-java-agent.jar outside /proc/<pid>/root, under the attacker-controlled host path.

Reproduction outline for the symlink clobber case:

1. Start a Java process with TMPDIR=/tmp or another writable temp directory.
2. Before injection occurs, create a symlink at the expected destination:
   • /tmp/obi-java-agent.jar -> /path/to/target/file
3. Trigger Java agent injection for that process.
4. Observe that the privileged injector opens the symlink target with truncate semantics and overwrites the linked file contents.

Code evidence:

• findTempDir(...) reads ie.FileInfo.Service.EnvVars["TMPDIR"]
• dirOK(...) validates using filepath.Join(root, dir)
• copyAgent(...) writes the JAR into the selected temp directory
• the vulnerable write uses os.OpenFile(..., os.O_WRONLY|os.O_CREATE|os.O_TRUNC, 0o644)

This is an arbitrary file overwrite / file clobber vulnerability in a privileged host component.

Affected users are deployments where:

• Java injection is enabled
• OBI runs with elevated privileges
• untrusted local workloads can run Java processes on the same host

An attacker who can control a local Java process may be able to overwrite host files writable by OBI, which can lead to:

• host integrity compromise
• service disruption or denial of service
• possible local privilege escalation depending on deployment details and overwritten targets

The issue is local rather than remote, but the impact is high because the vulnerable component operates with elevated privileges on the host.

Input manipulates file paths to reach files outside the intended directory, such as configuration or credential files. Typical impact: unauthorized file read or write outside the intended directory.

CVE-2026-41433 has a CVSS score of 8.4 (High). The vector is requires local access, low 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 (0.8.0); upgrading removes the vulnerable code path.

Kodem intelligence

Upgrade to https://github.com/open-telemetry/opentelemetry-ebpf-instrumentation/releases/tag/v0.8.0.

1. What is CVE-2026-41433? CVE-2026-41433 is a high-severity path traversal vulnerability in go.opentelemetry.io/obi (go), affecting versions >= 0.4.0, < 0.8.0. It is fixed in 0.8.0. Input manipulates file paths to reach files outside the intended directory, such as configuration or credential files.
2. How severe is CVE-2026-41433? CVE-2026-41433 has a CVSS score of 8.4 (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 go.opentelemetry.io/obi are affected by CVE-2026-41433? go.opentelemetry.io/obi (go) versions >= 0.4.0, < 0.8.0 is affected.
4. Is there a fix for CVE-2026-41433? Yes. CVE-2026-41433 is fixed in 0.8.0. Upgrade to this version or later.
5. Is CVE-2026-41433 exploitable, and should I be worried? Whether CVE-2026-41433 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-2026-41433 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-2026-41433? Upgrade go.opentelemetry.io/obi to 0.8.0 or later.