Unknown

CVE-2026-97921 — tracing: Free histogram the field rejected for a bad modifier

In the Linux kernel, the following vulnerability has been resolved: tracing: Free histogram the field rejected for a bad modifier Writing a hist trigger whose value or variable carries a modifier that is not allowed there leaks the fields that were built for it. __create_val_field() takes the field from parse_expr() and stores it in hist_data->fields[] only after the modifier checks have run: hist_field = parse_expr(hist_data, file, field_str, flags, var_name, &n_subexprs); ... if (hist_field->flags & HIST_FIELD_FL_VAR) { if (hist_field->flags & (...)) goto err; } else { if (hist_field->flags & (...)) goto err; } hist_data->fields[val_idx] = hist_field; Both checks jump past that store, and the err label returns without freeing anything. The error unwinds to create_hist_data(), which calls destroy_hist_data() -> destroy_hist_fields(), and that reaches a field only by walking fields[]. A field that never got there is unreachable. commit e0213434fe3e ("tracing: Do not let histogram values have some modifiers") set ret to -EINVAL and fell through to the store, which left the field owned by fields[] and freed along with the rest of hist_data. Splitting the check into a value case and a variable case replaced that fall-through with a goto that skips it. With CONFIG_DEBUG_KMEMLEAK, 200 writes of # echo 'hist:keys=prev_pid:vals=next_pid.log2' > \ events/sched/sched_switch/trigger each correctly rejected with -EINVAL, leave 332 unreferenced objects (63744 bytes) reported at create_hist_field(); 200 install and remove cycles of a valid trigger leave none. A '.log2' field is two allocations, since create_hist_field() puts the plain field in operands[0] of the log2 field, and both are reported. Use destroy_hist_field() rather than __destroy_hist_field() so that operands[0] is freed as well. It returns early for HIST_FIELD_FL_VAR_REF, which is what an operand owned by hist_data->var_refs[] needs; the rejected field itself is never a var ref, because a var ref never carries a modifier flag.

Published Sep 25, 2026 · Updated Oct 15, 2026 · Sources: NIST National Vulnerability Database, CVE Program (cve.org) e CISA ADP · CNA: Linux

Low

Who exploits it and how urgent it is

A 0–100 score combining confirmed exploitation, ransomware and APT use, public exploits, EPSS and severity.

No exploitation signal in the sources consulted so far.

How the score was calculated

EPSS 0.2% (30-day exploitation probability)+1

The score orders the patch queue; it does not replace your asset context (internet exposure, criticality, compensating controls).

Triage

Is it exploited, how likely is exploitation, what does it touch, and how severe do the sources call it.

Exploitation

Not confirmed

Not in CISA KEV — an absence of record, not proof it is unexploited.

EPSS FIRST

0.21%

ahead of 10% of scored CVEs · Oct 15, 2026

Affects

Linux

CVSS base

—

Score not published yet.

Remediation

Fixes and mitigations documented by the sources — linked to the original advisory.

No fix documented by the sources we poll. That does not mean none exists: check the vendor advisory.

First 24 hours

Ordered from the record’s own fields — exposure first, because you cannot patch what you have not found. A rule-generated starting point.

Identify exposed assets running the affected vendor/product/version combinations (Linux Linux).
No fix documented in the sources: reduce exposure and monitor the vendor advisory.
Search available logs for exploit probes, errors and authentication anomalies.

Affected scope

Vendor, product and versions as the sources word them.

Vendor	Product	Versions	Status	Source
Linux	Linux	≥ 7403630eb94c1d664fb873f967427ef2f6ee3699 and < a2652fcf96b63e9da04951e4e58e6a0672df695d≥ e30fbc618e97b38dbb49f1d44dcd0778d3f23b8c and < 3d42fed18b2c5707b6332ebe87b789fd768eb01b≥ e30fbc618e97b38dbb49f1d44dcd0778d3f23b8c and < e787361bb6b0026ea3eb4d3fa7a304c7fcb99555≥ e30fbc618e97b38dbb49f1d44dcd0778d3f23b8c and < b22dc0add7d72b8bd9cae3188db0dd65da1c8652≥ e30fbc618e97b38dbb49f1d44dcd0778d3f23b8c and < 891c21f6d5673b2a519b536243bfc6dd2d35beb6≥ e30fbc618e97b38dbb49f1d44dcd0778d3f23b8c and < 230234d12ce42ab04132a32c3a848f07a5d27a71version 8d505d06d7330f5d67d3e5e9e1c647fb0b10ddad≥ 6.1.33 and < 6.1.189 and 2 more ≥ 6.3.7 and < 6.4version 6.4	Vulnerable	CVE Program (cve.org) e CISA ADP

Detection

Read off the CVSS vector and the weakness class. Starting points, not tested rules.

Not enough vector or weakness data: use the affected application’s logs as a starting point.

application logs

Timeline

What happened to this CVE, newest first.

2026
Record published
Oct 15, 2026
Affected products added · linux/linux
Oct 15, 2026 · CVE Program (cve.org) e CISA ADP
Source status changed · → Received
Oct 15, 2026 · NIST National Vulnerability Database
Record created in this database
Oct 15, 2026 · NIST National Vulnerability Database
CVE published
Sep 25, 2026 · Linux

Source activity

Repeated readings are counted rather than listed.

1× Official description updated · Oct 15, 2026 – Oct 15, 2026

References

6 on the record

git.kernel.org/stable/c/a2652fcf96b63e9da04951e4e58e6a0672df695d
NIST National Vulnerability Database
git.kernel.org/stable/c/3d42fed18b2c5707b6332ebe87b789fd768eb01b
NIST National Vulnerability Database
git.kernel.org/stable/c/b22dc0add7d72b8bd9cae3188db0dd65da1c8652
NIST National Vulnerability Database
git.kernel.org/stable/c/891c21f6d5673b2a519b536243bfc6dd2d35beb6
NIST National Vulnerability Database
git.kernel.org/stable/c/e787361bb6b0026ea3eb4d3fa7a304c7fcb99555
NIST National Vulnerability Database
git.kernel.org/stable/c/230234d12ce42ab04132a32c3a848f07a5d27a71
NIST National Vulnerability Database

Elsewhere on this site

Linux
every CVE for this vendor

Related CVEs (same products)

Critical CVE-2026-99999 ipv4: validate checksum_start before completing checksum 1d
Unknown CVE-2026-98432 ipv4: free inet_opt and ireq_opt after an RCU grace period 1d
Unknown CVE-2026-98431 RDMA/uverbs: Fix mmap_lock/disassociation_lock circular dependency 2d
Unknown CVE-2026-98430 RDMA/efa: Keep admin queues alive while IRQ is registered 2d
Unknown CVE-2026-98429 RDMA/efa: Keep EQ resources alive while IRQ is registered 2d
Unknown CVE-2026-98428 ALSA: usb: 6fire: Avoid embedded URBs 2d

Not in any source we poll

Listed rather than left blank: an empty field and an unmeasured one look identical on screen, and only one is a reason to look elsewhere.

No CVSS score published by NVD, the CNA, CISA or GitHub so far.
No fixed version, patch or mitigation documented.
No CISA SSVC assessment.
No CWE classification.
No confirmed IOCs, IP addresses, domains, file hashes, or malware artifacts supplied.
No organization-specific asset inventory, compensating-control status, or patch deployment evidence supplied.
No exploit packet captures, log samples, or incident case IDs supplied.

Answered from this record

Text assembled only from the fields above — no additional claims.

What should defenders know first?

CVE-2026-97921 is "tracing: Free histogram the field rejected for a bad modifier", rated Unknown. It affects Linux (Linux); versions are in the scope table. It is not in CISA KEV, which does not rule out exploitation. EPSS 0.21% estimates the probability of exploitation in 30 days; neither replaces your asset context. First verify whether exposed or business-critical assets run the affected versions, apply vendor fixes or mitigations, and preserve logs for review.

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