CVE-2026-64368 (GCVE-0-2026-64368)

Vulnerability from cvelistv5 – Published: 2026-07-25 08:50 – Updated: 2026-08-05 12:41
VLAI
Title
mm/slab: do not limit zeroing to orig_size when only red zoning is enabled
Summary
In the Linux kernel, the following vulnerability has been resolved: mm/slab: do not limit zeroing to orig_size when only red zoning is enabled When init (zeroing) on allocation is requested, for kmalloc() we generally have to zero the full object size even if a smaller size is requested, in order to provide krealloc()'s __GFP_ZERO guarantees. But if we track the requested size, krealloc() uses that information to do the right thing, so we can zero only the requested size. With red zoning also enabled, any extra size became part of the red zone, so it must not be zeroed and thus we must zero only the requested size. However the current check is imprecise, and will trigger also when only SLAB_RED_ZONE is enabled without SLAB_STORE_USER (which enables tracking the requested size). This means enabling red zoning alone can compromise krealloc()'s __GFP_ZERO contract. Fix this by using slub_debug_orig_size() instead, which is the exact check for whether the requested size is tracked. We don't need to care if red zoning is also enabled or not. Also update and expand the comment accordingly.
Severity
8.1 (High)
CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:H
Assigner
References
Impacted products
Vendor Product Version
Linux Linux Affected: 9ce67395f5a0cdec6ce152d26bfda13b98b25c01 , < 6256899c3a34674bba6076884aedbba49fc695e4 (git)
Affected: 9ce67395f5a0cdec6ce152d26bfda13b98b25c01 , < 7e706d50fa119eead6376bf0ef973e8d73a96030 (git)
Affected: 9ce67395f5a0cdec6ce152d26bfda13b98b25c01 , < 2382971aaaef5bf85a651234c64906f59580b8be (git)
Affected: 9ce67395f5a0cdec6ce152d26bfda13b98b25c01 , < 0d18ccef142f04433dfb2a0c120cf223d2b8a42c (git)
Affected: 9ce67395f5a0cdec6ce152d26bfda13b98b25c01 , < 648927ceb84021a25a0fbd5673740956f318d534 (git)
Create a notification for this product.
Linux Linux Affected: 6.2
Unaffected: 0 , < 6.2 (semver)
Unaffected: 6.6.145 , ≤ 6.6.* (semver)
Unaffected: 6.12.96 , ≤ 6.12.* (semver)
Unaffected: 6.18.39 , ≤ 6.18.* (semver)
Unaffected: 7.1.4 , ≤ 7.1.* (semver)
Unaffected: 7.2-rc1 , ≤ * (original_commit_for_fix)
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Show details on NVD website
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{
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          "product": "Linux",
          "programFiles": [
            "mm/slub.c"
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          "versions": [
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              "version": "0",
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              "versionType": "semver"
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              "version": "6.12.96",
              "versionType": "semver"
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              "status": "unaffected",
              "version": "6.18.39",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "7.1.*",
              "status": "unaffected",
              "version": "7.1.4",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "*",
              "status": "unaffected",
              "version": "7.2-rc1",
              "versionType": "original_commit_for_fix"
            }
          ]
        }
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      "cpeApplicability": [
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          "nodes": [
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                  "versionStartIncluding": "6.2",
                  "vulnerable": true
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          "lang": "en",
          "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nmm/slab: do not limit zeroing to orig_size when only red zoning is enabled\n\nWhen init (zeroing) on allocation is requested, for kmalloc() we\ngenerally have to zero the full object size even if a smaller size is\nrequested, in order to provide krealloc()\u0027s __GFP_ZERO guarantees.\n\nBut if we track the requested size, krealloc() uses that information to\ndo the right thing, so we can zero only the requested size. With red\nzoning also enabled, any extra size became part of the red zone, so it\nmust not be zeroed and thus we must zero only the requested size.\n\nHowever the current check is imprecise, and will trigger also when only\nSLAB_RED_ZONE is enabled without SLAB_STORE_USER (which enables tracking\nthe requested size). This means enabling red zoning alone can compromise\nkrealloc()\u0027s __GFP_ZERO contract.\n\nFix this by using slub_debug_orig_size() instead, which is the exact\ncheck for whether the requested size is tracked. We don\u0027t need to care\nif red zoning is also enabled or not. Also update and expand the\ncomment accordingly."
        }
      ],
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            "baseSeverity": "HIGH",
            "vectorString": "CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:H",
            "version": "3.1"
          },
          "scenarios": [
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              "value": "AV:N - On an already-mounted CephFS client, a malicious or compromised monitor can deliver crafted MDS-map data over TCP that reaches ceph_mdsmap_decode(), krealloc(), and the vulnerable allocator behavior.\nAC:H - Exploitation requires the uncommon, attacker-uncontrolled configuration of SLUB red zoning without SLAB_STORE_USER. Once configured, the attacker controls allocation sizes and heap-grooming messages without needing an uncontrolled race.\nPR:N - The attacking network peer requires no local account or capability on the target, and legacy or unauthenticated Ceph monitor connections can deliver the map without verified credentials.\nUI:N - An already-mounted, long-lived CephFS client processes MDS-map updates asynchronously, requiring no victim action during exploitation.\nS:U - Successful exploitation compromises the kernel and host resources within the same security authority; it does not inherently cross a VM or equivalent boundary.\nC:H - The skipped allocation tail exposes stale kernel-heap contents as valid data, including a pointer that check_new_map() can dereference, creating arbitrary kernel-memory read and disclosure potential.\nI:H - Stale attacker-groomed counts and pointers can reach unchecked set_bit() operations and kfree(), enabling out-of-bounds writes, arbitrary frees, and potential control-flow hijacking.\nA:H - Invalid pointer dereferences, out-of-bounds stack writes, or freeing a stale pointer can cause a kernel oops or panic and can be triggered repeatedly by crafted map updates."
            }
          ]
        }
      ],
      "providerMetadata": {
        "dateUpdated": "2026-08-05T12:41:09.726Z",
        "orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
        "shortName": "Linux"
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        },
        {
          "url": "https://git.kernel.org/stable/c/648927ceb84021a25a0fbd5673740956f318d534"
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    "assignerShortName": "Linux",
    "cveId": "CVE-2026-64368",
    "datePublished": "2026-07-25T08:50:21.831Z",
    "dateReserved": "2026-07-19T15:36:31.783Z",
    "dateUpdated": "2026-08-05T12:41:09.726Z",
    "state": "PUBLISHED"
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      "date": "2026-08-10",
      "epss": "0.00417",
      "percentile": "0.34373"
    },
    "microsoft_vex": {
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      "cve": "CVE-2026-64368",
      "id": "msrc_CVE-2026-64368",
      "initial_release_date": "2026-07-26T01:06:31.000Z",
      "product_status:known_affected": "1",
      "source": "Microsoft CSAF VEX",
      "status": "final",
      "title": "mm/slab: do not limit zeroing to orig_size when only red zoning is enabled",
      "url": "https://msrc.microsoft.com/csaf/vex/2026/msrc_cve-2026-64368.json",
      "version": "2"
    },
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    "redhat_vex": {
      "aggregate_severity": "Moderate",
      "current_release_date": "2026-07-29T11:09:26+00:00",
      "cve": "CVE-2026-64368",
      "id": "CVE-2026-64368",
      "initial_release_date": "2026-07-25T00:00:00+00:00",
      "product_status:known_affected": "184",
      "product_status:known_not_affected": "91",
      "source": "Red Hat CSAF VEX",
      "status": "final",
      "title": "kernel: mm/slab: do not limit zeroing to orig_size when only red zoning is enabled",
      "url": "https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-64368.json",
      "version": "3"
    }
  }
}



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Forecast uses a logistic model when the trend is rising, or an exponential decay model when the trend is falling. Fitted via linearized least squares.

Sightings

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Nomenclature

  • Seen: The vulnerability was mentioned, discussed, or observed by the user.
  • Confirmed: The vulnerability has been validated from an analyst's perspective.
  • Published Proof of Concept: A public proof of concept is available for this vulnerability.
  • Exploited: The vulnerability was observed as exploited by the user who reported the sighting.
  • Patched: The vulnerability was observed as successfully patched by the user who reported the sighting.
  • Not exploited: The vulnerability was not observed as exploited by the user who reported the sighting.
  • Not confirmed: The user expressed doubt about the validity of the vulnerability.
  • Not patched: The vulnerability was not observed as successfully patched by the user who reported the sighting.


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