CVE-2025-71109 MIPS: ftrace: Fix memory corruption when kernel is located beyond 32 bits
A buffer overflow in the MIPS ftrace implementation causes memory corruption and kernel hangs when the kernel is located beyond 32 bits.
- Exploited in the wild
- Not known
- Login needed
- Any signed-in user
- Attackable
- Local or same network only
- Victim action needed
- Not needed
- Fix
- Available
What is CVE-2025-71109?
CVE-2025-71109 is a high-severity memory corruption vulnerability in Linux kernel, published on 14 Jan 2026. It can only be exploited from the same machine or local network, with no action from the victim.
Official description
In the Linux kernel, the following vulnerability has been resolved:
MIPS: ftrace: Fix memory corruption when kernel is located beyond 32 bits
Since commit e424054000878 ("MIPS: Tracing: Reduce the overhead of dynamic Function Tracer"), the macro UASM_i_LA_mostly has been used, and this macro can generate more than 2 instructions. At the same time, the code in ftrace assumes that no more than 2 instructions can be generated, which is why it stores them in an int[2] array. However, as previously noted, the macro UASM_i_LA_mostly (and now UASM_i_LA) causes a buffer overflow when _mcount is beyond 32 bits. This leads to corruption of the variables located in the __read_mostly section.
This corruption was observed because the variable __cpu_primary_thread_mask was corrupted, causing a hang very early during boot.
This fix prevents the corruption by avoiding the generation of instructions if they could exceed 2 instructions in length. Fortunately, insn_la_mcount is only used if the instrumented code is located outside the kernel code section, so dynamic ftrace can still be used, albeit in a more limited scope. This is still preferable to corrupting memory and/or crashing the kernel.
Weakness: CWE-787
Which versions are affected by CVE-2025-71109?
It affects 1 product.
Products include Linux kernel.
How do I fix CVE-2025-71109?
Apply the vendor's patch.
Upgrade to the fixed version. Memory-safe languages, compiler hardening and fuzzing prevent most new cases. More about Memory corruption.
Is CVE-2025-71109 being exploited?
There is no known exploitation of CVE-2025-71109 in the wild and no public exploit code.
Other vulnerabilities in Linux kernel
Sources
Also known as BELL-CVE-2025-71109, DEBIAN-CVE-2025-71109, GHSA-f8h3-qj6h-j2cj, ROOT-OS-DEBIAN-11-CVE-2025-71109, ROOT-OS-DEBIAN-12-CVE-2025-71109, ROOT-OS-DEBIAN-13-CVE-2025-71109 and 3 more.