Summary
In the Linux kernel, the following vulnerability has been resolved: x86/iopl: Cure TIFIOBITMAP...
In the Linux kernel, the following vulnerability has been resolved:
x86/iopl: Cure TIF_IO_BITMAP inconsistencies
io_bitmap_exit() is invoked from exit_thread() when a task exists or
when a fork fails. In the latter case the exit_thread() cleans up
resources which were allocated during fork().
io_bitmap_exit() invokes task_update_io_bitmap(), which in turn ends up
in tss_update_io_bitmap(). tss_update_io_bitmap() operates on the
current task. If current has TIF_IO_BITMAP set, but no bitmap installed,
tss_update_io_bitmap() crashes with a NULL pointer dereference.
There are two issues, which lead to that problem:
io_bitmap_exit() should not invoke task_update_io_bitmap() when
the task, which is cleaned up, is not the current task. That's a
clear indicator for a cleanup after a failed fork().A task should not have TIF_IO_BITMAP set and neither a bitmap
installed nor IOPL emulation level 3 activated.This happens when a kernel thread is created in the context of
a user space thread, which has TIF_IO_BITMAP set as the thread
flags are copied and the IO bitmap pointer is cleared.Other than in the failed fork() case this has no impact because
kernel threads including IO workers never return to user space and
therefore never invoke tss_update_io_bitmap().
Cure this by adding the missing cleanups and checks:
Prevent io_bitmap_exit() to invoke task_update_io_bitmap() if
the to be cleaned up task is not the current task.Clear TIF_IO_BITMAP in copy_thread() unconditionally. For user
space forks it is set later, when the IO bitmap is inherited in
io_bitmap_share().
For paranoia sake, add a warning into tss_update_io_bitmap() to catch
the case, when that code is invoked with inconsistent state.
Impact
The application dereferences a null pointer, causing a crash. Typical impact: denial of service via crash.
CVE-2025-38100 has a CVSS score of 5.5 (Medium). 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. No fixed version is listed yet, so configuration controls and monitoring matter more in the interim.
Affected versions
Security releases
Kodem intelligence
Severity tells you how bad this could be in the worst case. It does not tell you whether you are exposed. Exploitability and impact are functions of runtime truth: whether the vulnerable code is present, reachable, and actually executes in your application. A vulnerable package can sit in your dependency tree and never run.
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. Kodem's runtime-powered SCA identifies whether this CVE is reachable in your applications.
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Frequently Asked Questions
- What is CVE-2025-38100? CVE-2025-38100 is a medium-severity null pointer dereference vulnerability. No fixed version is listed yet. The application dereferences a null pointer, causing a crash.
- How severe is CVE-2025-38100? CVE-2025-38100 has a CVSS score of 5.5 (Medium). 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.
- Is there a fix for CVE-2025-38100? No fixed version is listed for CVE-2025-38100 yet. Monitor the advisory for updates and apply mitigations in the interim.
- Is CVE-2025-38100 exploitable, and should I be worried? Whether CVE-2025-38100 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
- What actually determines whether CVE-2025-38100 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.