{"id":"CVE-2026-97921","title":"In the Linux kernel, the following vulnerability has been resolved:\n\ntracing: Free histogram the field rejected for a bad modifier\n\nWriting a hist trigger whose value or variable carries a modifier that is\nnot allowed there leaks the fie…","summary":"In the Linux kernel, the following vulnerability has been resolved:\n\ntracing: Free histogram the field rejected for a bad modifier\n\nWriting a hist trigger whose value or variable carries a modifier that is\nnot allowed there leaks the fie…","severity":"none","vendor":"Linux","product":"Linux","affected":["Linux >= e30fbc618e97b38dbb49f1d44dcd0778d3f23b8c < e787361bb6b0026ea3eb4d3fa7a304c7fcb99555","Linux >= e30fbc618e97b38dbb49f1d44dcd0778d3f23b8c < b22dc0add7d72b8bd9cae3188db0dd65da1c8652","Linux >= e30fbc618e97b38dbb49f1d44dcd0778d3f23b8c < 891c21f6d5673b2a519b536243bfc6dd2d35beb6","Linux >= e30fbc618e97b38dbb49f1d44dcd0778d3f23b8c < 230234d12ce42ab04132a32c3a848f07a5d27a71","Linux 7403630eb94c1d664fb873f967427ef2f6ee3699","Linux 8d505d06d7330f5d67d3e5e9e1c647fb0b10ddad","Linux >= 6.1.33 < 6.2","Linux >= 6.3.7 < 6.4","Linux 6.4"],"published":"2026-09-25","updated":"2026-09-25","sourceUpdated":"2026-09-25T11:17:19.160","source":"NVD","sourceUrl":"https://nvd.nist.gov/vuln/detail/CVE-2026-97921","references":[{"url":"https://git.kernel.org/stable/c/230234d12ce42ab04132a32c3a848f07a5d27a71","label":"416baaa9-dc9f-4396-8d5f-8c081fb06d67"},{"url":"https://git.kernel.org/stable/c/891c21f6d5673b2a519b536243bfc6dd2d35beb6","label":"416baaa9-dc9f-4396-8d5f-8c081fb06d67"},{"url":"https://git.kernel.org/stable/c/b22dc0add7d72b8bd9cae3188db0dd65da1c8652","label":"416baaa9-dc9f-4396-8d5f-8c081fb06d67"},{"url":"https://git.kernel.org/stable/c/e787361bb6b0026ea3eb4d3fa7a304c7fcb99555","label":"416baaa9-dc9f-4396-8d5f-8c081fb06d67"}],"tags":["nvd","cve.org"],"ingestedAt":"2026-09-25T11:06:38.889Z","slug":"CVE-2026-97921","body":"## Overview\n\nIn the Linux kernel, the following vulnerability has been resolved:\n\ntracing: Free histogram the field rejected for a bad modifier\n\nWriting a hist trigger whose value or variable carries a modifier that is\nnot allowed there leaks the fields that were built for it.\n\n__create_val_field() takes the field from parse_expr() and stores it in\nhist_data->fields[] only after the modifier checks have run:\n\n\thist_field = parse_expr(hist_data, file, field_str, flags, var_name,\n\t\t\t\t&n_subexprs);\n\t...\n\tif (hist_field->flags & HIST_FIELD_FL_VAR) {\n\t\tif (hist_field->flags & (...))\n\t\t\tgoto err;\n\t} else {\n\t\tif (hist_field->flags & (...))\n\t\t\tgoto err;\n\t}\n\n\thist_data->fields[val_idx] = hist_field;\n\nBoth checks jump past that store, and the err label returns without\nfreeing anything. The error unwinds to create_hist_data(), which calls\ndestroy_hist_data() -> destroy_hist_fields(), and that reaches a field\nonly by walking fields[]. A field that never got there is unreachable.\n\ncommit e0213434fe3e (\"tracing: Do not let histogram values have some\nmodifiers\") set ret to -EINVAL and fell through to the store, which left\nthe field owned by fields[] and freed along with the rest of hist_data.\nSplitting the check into a value case and a variable case replaced that\nfall-through with a goto that skips it.\n\nWith CONFIG_DEBUG_KMEMLEAK, 200 writes of\n\n  # echo 'hist:keys=prev_pid:vals=next_pid.log2' > \\\n\t events/sched/sched_switch/trigger\n\neach correctly rejected with -EINVAL, leave 332 unreferenced objects\n(63744 bytes) reported at create_hist_field(); 200 install and remove\ncycles of a valid trigger leave none. A '.log2' field is two\nallocations, since create_hist_field() puts the plain field in\noperands[0] of the log2 field, and both are reported.\n\nUse destroy_hist_field() rather than __destroy_hist_field() so that\noperands[0] is freed as well. It returns early for HIST_FIELD_FL_VAR_REF,\nwhich is what an operand owned by hist_data->var_refs[] needs; the\nrejected field itself is never a var ref, because a var ref never carries\na modifier flag.\n\n## Remediation\n\nRefer to the linked advisories for vendor-supplied fixes and affected version ranges.","depth":"sunlit","depthScore":3,"depthScoreParts":{"impact":2.8,"likelihood":0,"exploitation":0,"ransomware":0},"changes":[]}