CVE-2026-0648: ThreadX OSEK Layer DoS Vulnerability

CVE-2026-0648 Overview

CVE-2026-0648 is an incorrect error-checking vulnerability in Eclipse ThreadX's OSEK compatibility layer that affects the CreateCounter() function. The vulnerability stems from a logic error when handling the return value of osek_get_counter(), where the code incorrectly checks for failure conditions. This mismatch causes the error handling branch to never execute, even when the counter pool is exhausted, leading to wild pointer creation and potential memory corruption.

Critical Impact

This vulnerability can cause denial-of-service conditions through repeated counter pool exhaustion and enables unauthorized memory access via wild pointer writes to illegal memory addresses.

Affected Products

• Eclipse ThreadX OSEK Compatibility Layer (threadx/utility/rtos_compatibility_layers/OSEK/tx_osek.c)

Discovery Timeline

• 2026-01-27 - CVE-2026-0648 published to NVD
• 2026-01-29 - Last updated in NVD database

Technical Details for CVE-2026-0648

Vulnerability Analysis

The vulnerability is categorized under CWE-253 (Incorrect Check of Function Return Value), which indicates that the software calls a function but fails to properly validate the return value for error conditions. In the context of embedded RTOS systems like ThreadX, this type of flaw is particularly dangerous as it can compromise system stability and security.

The CreateCounter() function in the OSEK compatibility layer checks if the returned counter ID equals 0u to determine failure. However, the osek_get_counter() function actually returns E_OS_SYS_STACK (defined as 12U) upon failure. This semantic mismatch means the error condition is never properly detected, allowing execution to continue with an invalid value.

When the counter pool becomes depleted, the code proceeds to cast the error code (12U) to an OSEK_COUNTER * pointer. This creates a wild pointer that, when dereferenced for member writes, results in memory operations targeting illegal addresses such as 0x0000000C. The consequences include immediate HardFaults on embedded systems or silent memory corruption that may manifest as unpredictable system behavior.

Root Cause

The root cause is an incorrect error-checking logic in the CreateCounter() function located in threadx/utility/rtos_compatibility_layers/OSEK/tx_osek.c. The function compares the return value against 0u to detect failure, but osek_get_counter() returns the error constant E_OS_SYS_STACK (value 12U) on failure, not zero. This mismatch prevents the error handling path from ever executing under failure conditions.

Attack Vector

The attack vector is local, requiring the attacker to have local access to the system running ThreadX with the OSEK compatibility layer. An attacker can exploit this vulnerability by:

1. Repeatedly calling counter creation functions to exhaust the counter pool
2. Once the pool is depleted, subsequent calls will return the error code that gets incorrectly processed
3. The error code is cast to a pointer, creating a wild pointer
4. Writes to this invalid pointer corrupt memory at predictable addresses (e.g., 0x0000000C)
5. This can trigger denial-of-service via HardFaults or enable further exploitation through memory corruption

The vulnerability mechanism involves the incorrect comparison logic where the return value check fails to match the actual error return semantics. When osek_get_counter() fails and returns E_OS_SYS_STACK (12U), the check if (cntr_id == 0u) evaluates to false, allowing execution to proceed with the invalid value. See the GitHub Security Advisory for technical details.

Detection Methods for CVE-2026-0648

Indicators of Compromise

• Unexpected HardFault exceptions on embedded devices running ThreadX with OSEK compatibility layer
• Memory corruption symptoms at low memory addresses, particularly around 0x0000000C
• Counter pool exhaustion events followed by system instability
• Abnormal patterns of counter creation API calls

Detection Strategies

• Monitor for HardFault or MemManage exceptions triggered by memory access violations at predictable low addresses
• Implement runtime checks for counter pool allocation status and alert on repeated allocation failures
• Add instrumentation to track CreateCounter() calls and correlate with counter pool exhaustion events
• Deploy static analysis tools to identify similar return value check mismatches in OSEK layer code

Monitoring Recommendations

• Enable exception logging on embedded systems to capture HardFault details and faulting addresses
• Monitor counter resource utilization and set alerts for approaching pool limits
• Implement watchdog mechanisms to detect and recover from system hangs caused by memory corruption
• Review audit logs for patterns indicating deliberate resource exhaustion attempts

How to Mitigate CVE-2026-0648

Immediate Actions Required

• Review and update the Eclipse ThreadX OSEK compatibility layer to the latest patched version
• Audit all deployments using the affected tx_osek.c file for exposure to this vulnerability
• Implement additional bounds checking around counter creation operations as a defense-in-depth measure
• Consider rate-limiting counter creation calls if application requirements permit

Patch Information

A security advisory has been published by Eclipse ThreadX addressing this vulnerability. The fix involves correcting the error-checking logic in CreateCounter() to properly compare against E_OS_SYS_STACK (12U) instead of 0u. Review the GitHub Security Advisory for patch details and updated releases.

Workarounds

• Implement application-level counter pool management to prevent pool exhaustion before calling CreateCounter()
• Add pre-check validation to ensure counter pool availability before allocation attempts
• Deploy custom wrapper functions around CreateCounter() that validate return values against all possible error codes
• Consider implementing memory protection units (MPU) to restrict writes to low memory addresses where corruption would occur

The recommended mitigation approach involves modifying the error check in CreateCounter() to properly validate against E_OS_SYS_STACK rather than zero. Review the security advisory for specific implementation guidance and contact Eclipse ThreadX maintainers for verified patches.