CVE-2026-41433 — obi
HIGHCVE-2026-41433 is a high-severity (CVSS 8.4) Path Traversal vulnerability in go.opentelemetry.io/obi. A fix is available for go.opentelemetry.io/obi — see the affected versions and patch details below.
OpenTelemetry eBPF Instrumentation: Privileged Java agent injection allows arbitrary host file overwrite via untrusted TMPDIR
Exploitation Status
Proof-of-concept exploit code exists
- CISA’s SSVC triage found public proof-of-concept exploit code for this CVE, though no confirmed active exploitation.
Exploitation and automatability from CISA’s SSVC triage for CVE-2026-41433.
EPSS Exploitation Probability
EPSS (Exploit Prediction Scoring System) is a daily probability model maintained by FIRST.org. It estimates the likelihood a CVE will be exploited in production environments within the next 30 days, derived from real-world threat intelligence signals.
How urgent is this, really
CVE-2026-41433 plotted by exploitation likelihood (EPSS) against impact (CVSS). The shaded corner — EPSS 50%+ and CVSS 7.0+ — is where this CVE doesn't sit, though severity or exploitability alone can still warrant action.
Where this sits among everything scored
Of 378,156 CVEs with a current EPSS score, this one falls in the < 10% band (highlighted). Real counts from FIRST.org, not a sample — log-scaled since the landscape is heavily right-skewed.
Real-World Exposure
go.opentelemetry.io/obiReal-time download stats are indexed for npm and PyPI packages. This vulnerability affects Go packages — download data is not available via public APIs for these ecosystems.
Description
Summary
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.
Remediation
Upgrade to https://github.com/open-telemetry/opentelemetry-ebpf-instrumentation/releases/tag/v0.8.0.
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:
- Untrusted
TMPDIRfrom the target process can escape the intended target root. - 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:
- Start a Java process with a controlled environment variable such as:
TMPDIR=/etc- or
TMPDIR=/proc/1/root/etc
- Ensure the process is discovered by OBI and selected for Java agent injection.
- Wait for the injector to stage the agent JAR.
- Observe that the injector attempts to write
obi-java-agent.jaroutside/proc/<pid>/root, under the attacker-controlled host path.
Reproduction outline for the symlink clobber case:
- Start a Java process with
TMPDIR=/tmpor another writable temp directory. - Before injection occurs, create a symlink at the expected destination:
/tmp/obi-java-agent.jar -> /path/to/target/file
- Trigger Java agent injection for that process.
- Observe that the privileged injector opens the symlink target with truncate semantics and overwrites the linked file contents.
Code evidence:
findTempDir(...)readsie.FileInfo.Service.EnvVars["TMPDIR"]dirOK(...)validates usingfilepath.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)
Impact
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.
Affected Packages
| Ecosystem | Package | Vulnerable range | Fix |
|---|---|---|---|
| 🐹Go | go.opentelemetry.io/obi | ≥ 0.4.0&&< 0.8.0 | 0.8.0go get go.opentelemetry.io/obi@v0.8.0 |
Detection & mitigation playbook
Open-source dependencyDetect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for go.opentelemetry.io/obi, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.
Fix
Update go.opentelemetry.io/obi to 0.8.0 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2026-41433 is resolved across your whole dependency graph.
Workarounds
If you can't upgrade right away: gate or disable the affected feature, validate untrusted input at the boundary, and avoid passing attacker-controlled data into the vulnerable path. O3's runtime protection blocks exploitation in production as an interim safeguard until the upgrade lands.
How O3 protects you
O3 Security's impact-aware SCA analyses which vulnerable code paths your application actually calls, so a match like CVE-2026-41433 can be triaged on real exposure rather than presence alone.
Tailored to CVE-2026-41433. Runtime protection reduces exposure until a permanent patch is applied and verified — it complements patching, it doesn't replace it.
Frequently Asked Questions
Is CVE-2026-41433 in your dependencies?
O3 Security finds CVE-2026-41433 across Go dependencies, including transitive ones, and its impact-aware SCA ranks findings by whether your code actually calls the vulnerable path.