{ "schema_version": "1.6.1", "id": "RPI-CVE-2026-99235", "modified": "2026-11-03T05:30:01Z", "upstream": [ "CVE-2026-99235" ], "published": "2026-11-02T15:14:24Z", "summary": "tracing: Save the event file instead of the compatible histogram", "details": "In the Linux kernel, the following vulnerability has been resolved:\n\ntracing: Save the event file instead of the compatible histogram\n\ncreate_field_var_hist() creates a histogram on the matched event to\nsupply a field variable, and records it on the target so it can be torn\ndown later:\n\n\thist_data = find_compatible_hist(target_hist_data, file);\n\t...\n\t/* Save the compatible histogram information */\n\tvar_hist->hist_data = hist_data;\n\nhist_data is not the histogram it creates. It is one that was already\nthere, whose keys the new one copies. The saved pointer has a single\nuser, unregister_field_var_hists(), which runs when the target is\nremoved:\n\n\tfile = hist_data->field_var_hists[i]->hist_data->event_file;\n\nfind_compatible_hist() matches on keys alone, so it can pick one with no\nvariables of its own. check_var_refs() then returns false and the user\ncan remove it while the target still points at it:\n\n BUG: KASAN: slab-use-after-free in event_hist_trigger_free+0x2b2/0x320\n Read of size 8 at addr ffff8880093b90e0 by task init/1\n\n Freed by task 1:\n kfree+0x154/0x420\n event_hist_trigger_free+0x1d5/0x320\n event_hist_trigger_parse+0x35f3/0x69e0\n trigger_process_regex+0x1a6/0x250\n\nSave the event file instead. It is all the dereference ever wanted, and\nit does not go away when the user removes a trigger.", "severity": [ { "type": "CVSS_V3", "score": "CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H" } ], "affected": [ { "package": { "ecosystem": "Raspberry Pi OS:12", "name": "linux" }, "versions": [ "1:6.1.47-1+rpt4" ], "ecosystem_specific": { "binaries": [ { "binary_name": "linux-image-6.1.0-rpi3-rpi-2712", "binary_version": "1:6.1.47-1+rpt4" }, { "binary_name": "linux-image-6.1.0-rpi3-rpi-v6", "binary_version": "1:6.1.47-1+rpt4" }, { "binary_name": "linux-image-6.1.0-rpi3-rpi-v7", "binary_version": "1:6.1.47-1+rpt4" }, { "binary_name": "linux-image-6.1.0-rpi3-rpi-v7l", "binary_version": "1:6.1.47-1+rpt4" }, { "binary_name": "linux-image-6.1.0-rpi3-rpi-v8", "binary_version": "1:6.1.47-1+rpt4" } ] }, "database_specific": { "per_version": { "1:6.1.47-1+rpt4": { "linux_commit": "655fc658a15ae7a6f37103754adb39ba52a9a14e", "upstream_version": "6.1.47", "assessment": "commit ancestry (strak rule)", "upstream_fixed": "6.1.191", "compiled_filter": false } } } } ], "references": [ { "type": "ADVISORY", "url": "https://www.cve.org/CVERecord?id=CVE-2026-99235" }, { "type": "FIX", "url": "https://git.kernel.org/stable/c/a6165126b1a1b26342b55be6eb6ee23af8756aba" }, { "type": "FIX", "url": "https://git.kernel.org/stable/c/173914501b97236d7ea7dc2af7f30feddd4e1436" }, { "type": "FIX", "url": "https://git.kernel.org/stable/c/ac815a379644b2ad5008a009a3516ada31b5dd82" }, { "type": "FIX", "url": "https://git.kernel.org/stable/c/8b307d64a60548e4a74cb746f74d7ed4bd49965e" }, { "type": "FIX", "url": "https://git.kernel.org/stable/c/7a111ba0d1b74c99bc8f096565dc71945f694254" }, { "type": "FIX", "url": "https://git.kernel.org/stable/c/3609ada3c12cecfb0ae5ee82ef4f86c5f18a2dea" }, { "type": "FIX", "url": "https://git.kernel.org/stable/c/9631dbccd3c649b567a5aafffea6b00634183997" }, { "type": "FIX", "url": "https://git.kernel.org/stable/c/7cafc82e6153f05a221be678cd649d02e06ba909" } ], "database_specific": { "source": "https://git.kernel.org/pub/scm/linux/security/vulns.git", "upstream_modified": "2026-11-02T16:03:24Z", "severity": { "source": "kernel CNA", "cvss_v3_score": 7.8, "cvss_v3_severity": "High", "scenario": "AV:L - The attacker-controlled hist text is written locally to events///trigger: event_trigger_write() -> trigger_process_regex() -> event_hist_trigger_parse() -> create_actions()/onmatch_create() -> trace_action_create_field_var() -> create_field_var_hist(). No remote protocol carries the keys or onmatch() field names that make find_compatible_hist() save the dangling pointer.\nAC:L - The attacker writes a keys-only hist on event A, an onmatch().trace() hist on event B so create_field_var_hist() stores A's hist_data, then '!hist' on A and on B. find_compatible_hist() matches keys only, so check_var_refs() lets A be removed; event_mutex serializes every write, with no race or victim state.\nPR:L - create_field_var_hist() is reached only after writes to a TRACE_MODE_WRITE (0640) trigger file and to synthetic_events; event_trigger_regex_open() and the synth file enforce LOCKDOWN_TRACEFS and DAC, not capable(). tracefs_parse_param() uid= is applied by tracefs_apply_options() onto those inodes, so a delegated non-root tracing owner can run the onmatch() sequence; userns cannot mount tracefs.\nUI:N - The attacker performs the compatible-hist write, the onmatch().trace() write that calls create_field_var_hist(), and both '!hist' removals themselves. No other user must mount media, open a file, or enable tracing.\nS:U - The slab use-after-free of the compatible hist_trigger_data is in the host kernel's tracing heap (event_hist_trigger_free()/unregister_field_var_hists()). It does not cross a VM, IOMMU, or sandbox boundary.\nC:H - unregister_field_var_hists() reads field_var_hists[i]->hist_data->event_file from the hist_trigger_data that event_hist_trigger_free() already kfree'd (KASAN 8-byte read). After reclaiming that slab, the attacker controls the pointer then walked as a trace_event_file, a use-after-free read primitive.\nI:H - That attacker-controlled event_file is passed to event_hist_trigger_parse(\"!hist\"), which list_del_rcu()s file->triggers and runs cmd_ops->free on objects taken from the sprayed hist_trigger_data, a heap write and control-flow primitive.\nA:H - The commit reproduces a KASAN slab-use-after-free in event_hist_trigger_free() when the target hist is removed after the compatible one. Without KASAN, the stale hist_data->event_file dereference oopses or panics the kernel." } } }