# CVE-2026-64458: mm/damon/ops-common: handle extreme intervals in damon_hot_score()

Status: published. Published: 2026-07-25. Updated: 2026-11-12.

In the Linux kernel, the following vulnerability has been resolved:

mm/damon/ops-common: handle extreme intervals in damon_hot_score()

Fix three issues in damon_hot_score() that comes from wrong handling of
extreme (zero or too high) monitoring intervals user setup.

When the user sets sampling interval zero, damon_max_nr_accesses(), which
is called from damon_hot_score(), causes a divide-by-zero.  Needless to
say, it is a problem.

When the user sets the aggregation interval zero, the function returns
zero.  It is wrong, since the real maximum nr_acceses in the setup should
be one.  Worse yet, it can cause another divide-by-zero from its caller,
damon_hot_score(), since it uses damon_max_nr_accesses() return value as a
denominator.

When the user sets the aggregation interval very high, damon_hot_score()
could return a value out of [0, DAMOS_MAX_SCORE] range.  Since the return
value is used as an index to the regions_score_histogram array, which is
DAMOS_MAX_SCORE+1 size, it causes out of bounds array access.

The issues can be relatively easily reproduced like below.  The sysfs
write permission is required, though.

    # ./damo start --damos_action lru_prio --damos_quota_space 100M \
            --damos_quota_interval 1s
    # cd /sys/kernel/mm/damon/admin/kdamonds/0
    # echo 0 > contexts/0/monitoring_attrs/intervals/sample_us
    # echo 0 > contexts/0/monitoring_attrs/intervals/aggr_us
    # echo commit > state
    # dmesg
    [...]
    [  131.329762] Oops: divide error: 0000 [#1] SMP NOPTI
    [...]
    [  131.336089] RIP: 0010:damon_hot_score+0x27/0xd0
    [...]

Fix the divide-by-zero intervals problems by explicitly handling the zero
intervals in damon_max_nr_accesses().  Fix the out-of-bound array access
by applying [0, DAMOS_MAX_SCORE] bounds before returning from
damon_hot_score().

The issue was discovered [1] by Sashiko.

## Remediation

- fix: The reporting source identifies this reference as a patch. Check the advisory for affected versions and supported release branches. (source: 416baaa9-dc9f-4396-8d5f-8c081fb06d67) — https://git.kernel.org/stable/c/35d4a3cf70a855b50e53189ac2f8463e20a02046
- fix: The reporting source identifies this reference as a patch. Check the advisory for affected versions and supported release branches. (source: 416baaa9-dc9f-4396-8d5f-8c081fb06d67) — https://git.kernel.org/stable/c/58321b4e6e4f0f412069ab27ccdd56292757343a
- fix: The reporting source identifies this reference as a patch. Check the advisory for affected versions and supported release branches. (source: 416baaa9-dc9f-4396-8d5f-8c081fb06d67) — https://git.kernel.org/stable/c/74fef68d521150281e36cdaa20e9e1ee3e3aa146
- fix: The reporting source identifies this reference as a patch. Check the advisory for affected versions and supported release branches. (source: 416baaa9-dc9f-4396-8d5f-8c081fb06d67) — https://git.kernel.org/stable/c/76e415ea88d20f022ed5cfcf78c50e156a267e91
- fix: The reporting source identifies this reference as a patch. Check the advisory for affected versions and supported release branches. (source: 416baaa9-dc9f-4396-8d5f-8c081fb06d67) — https://git.kernel.org/stable/c/9c8f31eaae6140ecadec0c07320498a944556de2
- fix: The reporting source identifies this reference as a patch. Check the advisory for affected versions and supported release branches. (source: 416baaa9-dc9f-4396-8d5f-8c081fb06d67) — https://git.kernel.org/stable/c/ef2ae10a4582bc92b7e944181bbd2f87f3d30f3a

## Affected products and versions

- Linux / Linux: ≥ 198f0f4c58b9f481e4e51c8c70a6ab9852bbab7f; < 58321b4e6e4f0f412069ab27ccdd56292757343a (affected, git); ≥ 198f0f4c58b9f481e4e51c8c70a6ab9852bbab7f; < 74fef68d521150281e36cdaa20e9e1ee3e3aa146 (affected, git); ≥ 198f0f4c58b9f481e4e51c8c70a6ab9852bbab7f; < ef2ae10a4582bc92b7e944181bbd2f87f3d30f3a (affected, git); ≥ 198f0f4c58b9f481e4e51c8c70a6ab9852bbab7f; < 9c8f31eaae6140ecadec0c07320498a944556de2 (affected, git); ≥ 198f0f4c58b9f481e4e51c8c70a6ab9852bbab7f; < 76e415ea88d20f022ed5cfcf78c50e156a267e91 (affected, git); ≥ 198f0f4c58b9f481e4e51c8c70a6ab9852bbab7f; < 35d4a3cf70a855b50e53189ac2f8463e20a02046 (affected, git). Source: CNA: Linux
- Linux / Linux: 5.16 (affected); ≥ 0; < 5.16 (unaffected, semver); ≥ 6.1.178; ≤ 6.1.* (unaffected, semver); ≥ 6.6.145; ≤ 6.6.* (unaffected, semver); ≥ 6.12.96; ≤ 6.12.* (unaffected, semver); ≥ 6.18.39; ≤ 6.18.* (unaffected, semver); ≥ 7.1.4; ≤ 7.1.* (unaffected, semver); ≥ 7.2; ≤ * (unaffected, original_commit_for_fix). Source: CNA: Linux

## NVD configuration conditions

Affected CPE matches depend on the following AND/OR and negation conditions:

```json
[
  {
    "negate": false,
    "nodes": [
      {
        "cpeMatch": [
          {
            "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
            "versionEndExcluding": "6.1.178",
            "versionStartIncluding": "5.16",
            "vulnerable": true
          },
          {
            "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
            "versionEndExcluding": "6.6.145",
            "versionStartIncluding": "6.2",
            "vulnerable": true
          },
          {
            "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
            "versionEndExcluding": "6.12.96",
            "versionStartIncluding": "6.7",
            "vulnerable": true
          },
          {
            "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
            "versionEndExcluding": "6.18.39",
            "versionStartIncluding": "6.13",
            "vulnerable": true
          },
          {
            "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
            "versionEndExcluding": "7.1.4",
            "versionStartIncluding": "6.19",
            "vulnerable": true
          },
          {
            "criteria": "cpe:2.3:o:linux:linux_kernel:7.2:rc1:*:*:*:*:*:*",
            "vulnerable": true
          },
          {
            "criteria": "cpe:2.3:o:linux:linux_kernel:7.2:rc2:*:*:*:*:*:*",
            "vulnerable": true
          }
        ],
        "negate": false,
        "operator": "OR"
      }
    ],
    "operator": "OR"
  }
]
```

## Severity and prioritization

- CVSS 3.1: 5.5 (medium); CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H; source: NVD: nvd@nist.gov

- CISA KEV: No listing in collected sources

- EPSS: 0.18% as of 2026-11-10; percentile 7.67%

- SSVC: exploitation none; automatable no; technical impact partial; source ADP: CISA-ADP

- Weaknesses: CWE-369

## Exploit evidence

No exploit evidence in collected sources. This is not proof of no exploitation.

## References

- https://git.kernel.org/stable/c/58321b4e6e4f0f412069ab27ccdd56292757343a (CNA: Linux)

- https://git.kernel.org/stable/c/74fef68d521150281e36cdaa20e9e1ee3e3aa146 (CNA: Linux)

- https://git.kernel.org/stable/c/ef2ae10a4582bc92b7e944181bbd2f87f3d30f3a (CNA: Linux)

- https://git.kernel.org/stable/c/9c8f31eaae6140ecadec0c07320498a944556de2 (CNA: Linux)

- https://git.kernel.org/stable/c/76e415ea88d20f022ed5cfcf78c50e156a267e91 (CNA: Linux)

- https://git.kernel.org/stable/c/35d4a3cf70a855b50e53189ac2f8463e20a02046 (CNA: Linux)

- https://git.kernel.org/stable/c/35d4a3cf70a855b50e53189ac2f8463e20a02046 (416baaa9-dc9f-4396-8d5f-8c081fb06d67; Patch)

- https://git.kernel.org/stable/c/58321b4e6e4f0f412069ab27ccdd56292757343a (416baaa9-dc9f-4396-8d5f-8c081fb06d67; Patch)

- https://git.kernel.org/stable/c/74fef68d521150281e36cdaa20e9e1ee3e3aa146 (416baaa9-dc9f-4396-8d5f-8c081fb06d67; Patch)

- https://git.kernel.org/stable/c/76e415ea88d20f022ed5cfcf78c50e156a267e91 (416baaa9-dc9f-4396-8d5f-8c081fb06d67; Patch)

- https://git.kernel.org/stable/c/9c8f31eaae6140ecadec0c07320498a944556de2 (416baaa9-dc9f-4396-8d5f-8c081fb06d67; Patch)

- https://git.kernel.org/stable/c/ef2ae10a4582bc92b7e944181bbd2f87f3d30f3a (416baaa9-dc9f-4396-8d5f-8c081fb06d67; Patch)

## Provenance

- CNA: Linux: https://www.cve.org/CVERecord?id=CVE-2026-64458; retrieved 2026-11-06; source updated 2026-11-06

- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-64458; retrieved 2026-11-12; source updated 2026-11-12

- FIRST EPSS: https://api.first.org/data/v1/epss?cve=CVE-2026-64458; retrieved 2026-11-12; source updated Not reported

Revision: 3b75f7eb5d4816a77280ba67c4d1cfd53e5d60b7b834374a553dff1b22fcbb85

Canonical: https://y2.dev/cve/CVE-2026-64458

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