Описание
In the Linux kernel, the following vulnerability has been resolved:
tracing: Save the event file instead of the compatible histogram
create_field_var_hist() creates a histogram on the matched event to
supply a field variable, and records it on the target so it can be torn
down later:
hist_data = find_compatible_hist(target_hist_data, file);
...
/* Save the compatible histogram information */
var_hist->hist_data = hist_data;
hist_data is not the histogram it creates. It is one that was already
there, whose keys the new one copies. The saved pointer has a single
user, unregister_field_var_hists(), which runs when the target is
removed:
file = hist_data->field_var_hists[i]->hist_data->event_file;
find_compatible_hist() matches on keys alone, so it can pick one with no
variables of its own. check_var_refs() then returns false and the user
can remove it while the target still points at it:
BUG: KASAN: slab-use-after-free in event_hist_trigger_free+0x2b2/0x320
Read of size 8 at addr ffff8880093b90e0 by task init/1
Freed by task 1:
kfree+0x154/0x420
event_hist_trigger_free+0x1d5/0x320
event_hist_trigger_parse+0x35f3/0x69e0
trigger_process_regex+0x1a6/0x250
Save the event file instead. It is all the dereference ever wanted, and
it does not go away when the user removes a trigger.
A flaw was found in the Linux kernel's event tracing subsystem. A local user with permissions to configure trace event triggers could exploit this flaw to achieve privilege escalation or cause a Denial of Service (DoS). The issue occurs when the kernel improperly retains a reference to compatible histogram data, allowing that data to be freed while still referenced by another trigger. When the remaining trigger is subsequently unregistered, the kernel accesses the freed memory, resulting in a use-after-free condition that can crash the system or enable unauthorized code execution.
Отчет
Red Hat has evaluated this vulnerability as having an Important severity impact because successful exploitation can allow a local user to compromise the kernel space or trigger a system-wide denial of service, elevating privileges beyond standard user boundaries. On typical Red Hat Enterprise Linux installations, the event tracing filesystem interface is protected by default file permissions and restricted to administrative accounts, which inherently limits general exposure. However, in environments where tracing capabilities or filesystem permissions are explicitly delegated to unprivileged accounts, an attacker can manipulate event triggers to induce memory corruption.
Меры по смягчению последствий
--- CME Mitigation Guidance (2026-11-04) --- Disclaimer: The following mitigation solutions are provided as a courtesy, pending the application of an official patch. This content was generated utilizing AI tools in conjunction with data from https://cmetaxonomy.org. Customers are advised to independently evaluate and test these temporary mitigations within their own infrastructure. The highest-value action is to restrict write permissions to tracefs and event trigger configuration files to trusted administrators: upgrade to the corresponding fixed Red Hat builds, which save a direct pointer to trace_event_file instead of the compatible histogram pointer in struct field_var_hist, closing all 2 injection vectors (trace event trigger manipulation, premature deletion of a referenced compatible histogram trigger). Until patched, this is only a concern on Linux systems where local users have write permissions to configure trace event triggers — Non-Linux operating systems are unaffected — so restrict and audit write access to tracefs and event trigger control files to prevent unprivileged accounts from creating and deleting histogram triggers. As a compensating measure, enable runtime memory error detection such as KASAN or HWASan to detect slab use-after-free violations during trigger unregistration, enable KASLR to randomize kernel base addresses and hinder reliable execution redirection, enforce SMEP to prevent the kernel from executing userspace code if instruction pointers are redirected, enforce SMAP to block the kernel from accessing attacker-controlled userspace memory structures, enable Control Flow Integrity or Shadow Call Stack to validate indirect call targets within the kernel, and enable slab freelist hardening with freelist randomization and integrity checks to impede exploitation of freed heap memory. These controls limit blast radius and contain exploitation, but they do not fix the underlying slab use-after-free defect — apply the upstream patch to fully remediate. Highest-impact CME: CME-301 SELinux (Enforcing Mode) (medium)
Затронутые пакеты
| Платформа | Пакет | Состояние | Рекомендация | Релиз |
|---|---|---|---|---|
| Red Hat Enterprise Linux 10 | kernel | Affected | ||
| Red Hat Enterprise Linux 6 | kernel | Not affected | ||
| Red Hat Enterprise Linux 7 | kernel | Not affected | ||
| Red Hat Enterprise Linux 7 | kernel-rt | Not affected | ||
| Red Hat Enterprise Linux 8 | kernel | Affected | ||
| Red Hat Enterprise Linux 8 | kernel-rt | Affected | ||
| Red Hat Enterprise Linux 9 | kernel | Affected | ||
| Red Hat Enterprise Linux 9 | kernel-rt | Affected | ||
| Red Hat OpenShift Container Platform 4 | openshift/ose-rhel-coreos-8 | Affected | ||
| Red Hat OpenShift Container Platform 4 | openshift/ose-rhel-coreos-9 | Affected |
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Дополнительная информация
Статус:
EPSS
7.8 High
CVSS3
Связанные уязвимости
In the Linux kernel, the following vulnerability has been resolved: tracing: Save the event file instead of the compatible histogram create_field_var_hist() creates a histogram on the matched event to supply a field variable, and records it on the target so it can be torn down later: hist_data = find_compatible_hist(target_hist_data, file); ... /* Save the compatible histogram information */ var_hist->hist_data = hist_data; hist_data is not the histogram it creates. It is one that was already there, whose keys the new one copies. The saved pointer has a single user, unregister_field_var_hists(), which runs when the target is removed: file = hist_data->field_var_hists[i]->hist_data->event_file; find_compatible_hist() matches on keys alone, so it can pick one with no variables of its own. check_var_refs() then returns false and the user can remove it while the target still points at it: BUG: KASAN: slab-use-after-free in event_hist_trigger_free+0x2b2/0x320 Read of size 8 at addr ffff8...
In the Linux kernel, the following vulnerability has been resolved: tracing: Save the event file instead of the compatible histogram create_field_var_hist() creates a histogram on the matched event to supply a field variable, and records it on the target so it can be torn down later: hist_data = find_compatible_hist(target_hist_data, file); ... /* Save the compatible histogram information */ var_hist->hist_data = hist_data; hist_data is not the histogram it creates. It is one that was already there, whose keys the new one copies. The saved pointer has a single user, unregister_field_var_hists(), which runs when the target is removed: file = hist_data->field_var_hists[i]->hist_data->event_file; find_compatible_hist() matches on keys alone, so it can pick one with no variables of its own. check_var_refs() then returns false and the user can remove it while the target still points at it: BUG: KASAN: slab-use-after-free in event_hist_trigger_free+0x2b2/0x320 Read of size 8 at
tracing: Save the event file instead of the compatible histogram
In the Linux kernel, the following vulnerability has been resolved: t ...
In the Linux kernel, the following vulnerability has been resolved: tracing: Save the event file instead of the compatible histogram create_field_var_hist() creates a histogram on the matched event to supply a field variable, and records it on the target so it can be torn down later: hist_data = find_compatible_hist(target_hist_data, file); ... /* Save the compatible histogram information */ var_hist->hist_data = hist_data; hist_data is not the histogram it creates. It is one that was already there, whose keys the new one copies. The saved pointer has a single user, unregister_field_var_hists(), which runs when the target is removed: file = hist_data->field_var_hists[i]->hist_data->event_file; find_compatible_hist() matches on keys alone, so it can pick one with no variables of its own. check_var_refs() then returns false and the user can remove it while the target still points at it: BUG: KASAN: slab-use-after-free in event_hist_trigger_free+0x2b2/0x320 Read of size 8...
EPSS
7.8 High
CVSS3