CVE-2026-121994

A flaw was found in the GNU debugger (GDB). When GDB connects to a remote debug target, a malicious target can cause GDB to overflow a buffer on the stack while parsing the target's replies, which can crash GDB or potentially allow the target to execute arbitrary code in the GDB client process with the privileges of the user running GDB.

A stack buffer overflow in the GDB client's tracepoint upload handler allows an attacker-controlled debug stub to corrupt stack memory automatically during connection setup. The overflow results from GDB reading beyond the current reply boundary into a stale prior reply in the shared packet buffer.

A flaw was found in GDB's STABS debug format parser. The read_member_functions() function in gdb/stabsread.c contains a linked list removal bug in the code that separates destructor and non-destructor member functions of C++ classes. The bug causes the destructor entries to remain in the main function list while the list length counter is decremented, resulting in an out-of-bounds write when the function list is copied to its final allocated array. An attacker can craft an ELF binary with malicious .stab and .stabstr sections that triggers this out-of-bounds write when a user opens the file in GDB and performs any symbol-inspection operation such as setting a breakpoint. The inferior process does not need to be executed. Under controlled conditions, this was demonstrated to achieve execution of arbitrary commands within the GDB process.