{"id":"DEBIAN-CVE-2026-64451","details":"In the Linux kernel, the following vulnerability has been resolved:  tracing: Fix NULL pointer dereference in func_set_flag()  func_set_flag() dereferences tr-\u003ecurrent_trace_flags before verifying that the current tracer is actually the function tracer. When the active tracer has been switched away from \"function\" (e.g., to \"wakeup_rt\"), tr-\u003ecurrent_trace_flags can be NULL, leading to a NULL pointer dereference and kernel crash.  The call chain that triggers this is:    trace_options_write()     -\u003e __set_tracer_option()       -\u003e trace-\u003eset_flag()          /* func_set_flag */  In func_set_flag(), the first operation is:    if (!!set == !!(tr-\u003ecurrent_trace_flags-\u003eval & bit))  This dereferences tr-\u003ecurrent_trace_flags unconditionally. The safety check that guards against a non-function tracer:    if (tr-\u003ecurrent_trace != &function_trace)       return 0;  is placed *after* the dereference, which is too late.  This was observed with the following crash dump:    BUG: unable to handle page fault at 0000000000000000   RIP: func_set_flag+0xd    Call Trace:    __set_tracer_option+0x27    trace_options_write+0x75    vfs_write+0x12a    ksys_write+0x66    do_syscall_64+0x5b    RIP: ffffffff914c973d  RSP: ff67ec88b01dfdf0  RFLAGS: 00010202   RAX: 0000000000000000  RBX: ff3a826e80354580  RCX: 0000000000000001   RDX: 0000000000000001  RSI: 0000000000000000  RDI: ffffffff93918080  The disassembly confirms the fault:    func_set_flag+0:   mov 0x1f08(%rdi), %rax  ; RAX = tr-\u003ecurrent_trace_flags = NULL   func_set_flag+13:  mov (%rax), %eax        ; page fault: dereference NULL  At the time of the crash:   tr-\u003ecurrent_trace_flags = 0x0 (NULL)   tr-\u003ecurrent_trace = wakeup_rt_tracer (not function_trace)  The scenario is that a process opens a function tracer option file (such as \"func_stack_trace\"), then the current tracer is switched to another tracer (e.g., \"wakeup_rt\"), which sets current_trace_flags to NULL. When the process subsequently writes to the option file, func_set_flag() is invoked and crashes on the NULL dereference.  Fix this by moving the current_trace check before the current_trace_flags dereference, so that func_set_flag() returns early when the function tracer is not active.","modified":"2026-09-14T17:03:48.639734476Z","published":"2026-07-25T10:17:30.013Z","upstream":["CVE-2026-64451"],"references":[{"type":"ADVISORY","url":"https://security-tracker.debian.org/tracker/CVE-2026-64451"}],"affected":[{"package":{"name":"linux","ecosystem":"Debian:14","purl":"pkg:deb/debian/linux?arch=source&distro=forky"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"fixed":"7.1.4-1"}]}],"versions":["6.12.100-1","6.12.101-1","6.12.105-1","6.12.107-1","6.12.38-1","6.12.41-1","6.12.43-1","6.12.43-1~bpo12+1","6.12.48-1","6.12.57-1","6.12.57-1~bpo12+1","6.12.63-1","6.12.63-1~bpo12+1","6.12.69-1","6.12.69-1~bpo12+1","6.12.73-1","6.12.73-1~bpo12+1","6.12.74-1","6.12.74-2","6.12.74-2~bpo12+1","6.12.85-1","6.12.85-1~bpo12+1","6.12.86-1","6.12.86-1~bpo12+1","6.12.88-1","6.12.88-1~bpo12+1","6.12.90-1","6.12.90-1~bpo12+1","6.12.90-2","6.12.90-2~bpo12+1","6.12.94-1","6.12.94-1~bpo12+1","6.12.95-1","6.12.95-1~bpo12+1","6.12.96-1","6.13.10-1~exp1","6.13.11-1~exp1","6.13.2-1~exp1","6.13.3-1~exp1","6.13.4-1~exp1","6.13.5-1~exp1","6.13.6-1~exp1","6.13.7-1~exp1","6.13.8-1~exp1","6.13.9-1~exp1","6.13~rc6-1~exp1","6.13~rc7-1~exp1","6.14.3-1~exp1","6.14.5-1~exp1","6.14.6-1~exp1","6.15-1~exp1","6.15.1-1~exp1","6.15.2-1~exp1","6.15.3-1~exp1","6.15.4-1~exp1","6.15.5-1~exp1","6.15.6-1~exp1","6.15~rc7-1~exp1","6.16-1~exp1","6.16.1-1~exp1","6.16.10-1","6.16.11-1","6.16.12-1","6.16.12-1~bpo13+1","6.16.12-2","6.16.3-1","6.16.3-1~bpo13+1","6.16.5-1","6.16.6-1","6.16.7-1","6.16.8-1","6.16.9-1","6.16~rc7-1~exp1","6.17.10-1","6.17.11-1","6.17.12-1","6.17.13-1","6.17.13-1~bpo13+1","6.17.2-1~exp1","6.17.5-1~exp1","6.17.6-1","6.17.7-1","6.17.7-2","6.17.8-1","6.17.8-1~bpo13+1","6.17.9-1","6.18.1-1~exp1","6.18.10-1","6.18.12-1","6.18.12-1~bpo13+1","6.18.13-1","6.18.14-1","6.18.15-1","6.18.15-1~bpo13+1","6.18.2-1~exp1","6.18.3-1","6.18.5-1","6.18.5-1~bpo13+1","6.18.8-1","6.18.9-1","6.18.9-1~bpo13+1","6.18~rc4-1~exp1","6.18~rc4-1~exp2","6.18~rc5-1~exp1","6.18~rc6-1~exp1","6.18~rc7-1~exp1","6.19-1~exp1","6.19.10-1","6.19.10-1~bpo13+1","6.19.11-1","6.19.11-1~bpo13+1","6.19.12-1","6.19.13-1","6.19.13-1~bpo13+1","6.19.14-1","6.19.14-1~bpo13+1","6.19.2-1~exp1","6.19.3-1~exp1","6.19.4-1~exp1","6.19.5-1~exp1","6.19.6-1","6.19.6-2","6.19.6-2~bpo13+1","6.19.8-1","6.19.8-1~bpo13+1","6.19~rc4-1~exp1","6.19~rc5-1~exp1","6.19~rc6-1~exp1","6.19~rc7-1~exp1","6.19~rc8-1~exp1","7.0-1~exp1","7.0.1-1~exp1","7.0.10-1","7.0.10-1~bpo13+1","7.0.12-1","7.0.12-2","7.0.12-2~bpo13+1","7.0.13-1","7.0.13-1~bpo13+1","7.0.14-1","7.0.3-1","7.0.4-1","7.0.4-1~bpo13+1","7.0.7-1","7.0.7-1~bpo13+1","7.0.9-1","7.0.9-1~bpo13+1","7.1.1-1~exp1","7.1.2-1~exp1","7.1.3-1","7.1.3-1+sunvdc","7.1.3-1~bpo13+1","7.1~rc2-1~exp1","7.1~rc3-1~exp1","7.1~rc4-1~exp1","7.1~rc4-1~exp2","7.1~rc5-1~exp1","7.1~rc7-1~exp1"],"ecosystem_specific":{"urgency":"not yet assigned"},"database_specific":{"source":"https://storage.googleapis.com/debian-osv/debian-cve-osv/DEBIAN-CVE-2026-64451.json"}}],"schema_version":"1.9.0","severity":[{"type":"CVSS_V3","score":"CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H"}]}