CVE-2025-40245 (GCVE-0-2025-40245)

Vulnerability from cvelistv5 – Published: 2025-12-04 15:31 – Updated: 2026-08-05 12:08
VLAI
Title
nios2: ensure that memblock.current_limit is set when setting pfn limits
Summary
In the Linux kernel, the following vulnerability has been resolved: nios2: ensure that memblock.current_limit is set when setting pfn limits On nios2, with CONFIG_FLATMEM set, the kernel relies on memblock_get_current_limit() to determine the limits of mem_map, in particular for max_low_pfn. Unfortunately, memblock.current_limit is only default initialized to MEMBLOCK_ALLOC_ANYWHERE at this point of the bootup, potentially leading to situations where max_low_pfn can erroneously exceed the value of max_pfn and, thus, the valid range of available DRAM. This can in turn cause kernel-level paging failures, e.g.: [ 76.900000] Unable to handle kernel paging request at virtual address 20303000 [ 76.900000] ea = c0080890, ra = c000462c, cause = 14 [ 76.900000] Kernel panic - not syncing: Oops [ 76.900000] ---[ end Kernel panic - not syncing: Oops ]--- This patch fixes this by pre-calculating memblock.current_limit based on the upper limits of the available memory ranges via adjust_lowmem_bounds, a simplified version of the equivalent implementation within the arm architecture.
Severity
7.8 (High)
CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
Assigner
Linux CNA under the mitre root
CNA scorecard D 53/100 over 7033 records in the last 180 days details
References
Impacted products
Vendor Product Version CPE status
Linux Linux Affected: 7f7bc20bc41a4fbcd2db75b375ac95e5faf958ae , < 25f09699edd360b534ccae16bc276c3b52c471f3 (git)
Affected: 7f7bc20bc41a4fbcd2db75b375ac95e5faf958ae , < 5c3e38a367822f036227dd52bac82dc4a05157e2 (git)
Affected: 7f7bc20bc41a4fbcd2db75b375ac95e5faf958ae , < b1ec9faef7e36269ca3ec890972a78effbaeb975 (git)
Affected: 7f7bc20bc41a4fbcd2db75b375ac95e5faf958ae , < 90f5f715550e07cd6a51f80fc3f062d832c8c997 (git)
Affected: 7f7bc20bc41a4fbcd2db75b375ac95e5faf958ae , < 8912814f14e298b83df072fecc1f7ed1b63b1b2c (git)
Affected: 7f7bc20bc41a4fbcd2db75b375ac95e5faf958ae , < a20b83cf45be2057f3d073506779e52c7fa17f94 (git)
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Linux Linux Affected: 5.12
Unaffected: 0 , < 5.12 (semver)
Unaffected: 5.15.196 , ≤ 5.15.* (semver)
Unaffected: 6.1.158 , ≤ 6.1.* (semver)
Unaffected: 6.6.115 , ≤ 6.6.* (semver)
Unaffected: 6.12.56 , ≤ 6.12.* (semver)
Unaffected: 6.17.6 , ≤ 6.17.* (semver)
Unaffected: 6.18 , ≤ * (original_commit_for_fix)
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{
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          "product": "Linux",
          "programFiles": [
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              "status": "unaffected",
              "version": "6.1.158",
              "versionType": "semver"
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              "status": "unaffected",
              "version": "6.6.115",
              "versionType": "semver"
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              "version": "6.12.56",
              "versionType": "semver"
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              "version": "6.17.6",
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              "status": "unaffected",
              "version": "6.18",
              "versionType": "original_commit_for_fix"
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      ],
      "cpeApplicability": [
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          "nodes": [
            {
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              "operator": "OR"
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      "descriptions": [
        {
          "lang": "en",
          "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nnios2: ensure that memblock.current_limit is set when setting pfn limits\n\nOn nios2, with CONFIG_FLATMEM set, the kernel relies on\nmemblock_get_current_limit() to determine the limits of mem_map, in\nparticular for max_low_pfn.\nUnfortunately, memblock.current_limit is only default initialized to\nMEMBLOCK_ALLOC_ANYWHERE at this point of the bootup, potentially leading\nto situations where max_low_pfn can erroneously exceed the value of\nmax_pfn and, thus, the valid range of available DRAM.\n\nThis can in turn cause kernel-level paging failures, e.g.:\n\n[   76.900000] Unable to handle kernel paging request at virtual address 20303000\n[   76.900000] ea = c0080890, ra = c000462c, cause = 14\n[   76.900000] Kernel panic - not syncing: Oops\n[   76.900000] ---[ end Kernel panic - not syncing: Oops ]---\n\nThis patch fixes this by pre-calculating memblock.current_limit\nbased on the upper limits of the available memory ranges via\nadjust_lowmem_bounds, a simplified version of the equivalent\nimplementation within the arm architecture."
        }
      ],
      "metrics": [
        {
          "cvssV3_1": {
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            "baseSeverity": "HIGH",
            "vectorString": "CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H",
            "version": "3.1"
          },
          "scenarios": [
            {
              "lang": "en",
              "value": "AV:L - The defect is in nios2 `setup_arch()` boot-time memory initialization, and its consequences are realized through local activity \u2014 memory allocation and `mmap()`/page-fault paths that call `pfn_valid()`/`pfn_to_page()`. There is no network or remote-peer path to arch/nios2/kernel/setup.c.\nAC:L - `memblock.current_limit` is never set before `find_limits()`, so `max_low_pfn`/`max_mapnr` are unconditionally inflated to ~4 GB of PFNs on every affected nios2 system \u2014 the vulnerable state always exists, with no race and no memory-layout luck required. The attacker only needs to map or touch a physical region above DRAM, which is under their control on these FPGA SoCs where peripheral/on-chip-memory windows sit above RAM.\nPR:L - No capability check guards any of it \u2014 an ordinary unprivileged process reaching `update_mmu_cache_range()`/`flush_dcache_page()` through a fault on a device or PFNMAP mapping, or simply driving allocation into the bogus PFN range, is sufficient. Embedded nios2 deployments routinely expose UIO/framebuffer device nodes to non-root users.\nUI:N - The attacker performs every step themselves \u2014 map the region, touch it, let the fault path run. No action by another user or administrator is needed.\nS:U - The out-of-bounds accesses stay within the kernel\u0027s own memory and security authority; no VM, IOMMU, or sandbox boundary is crossed.\nC:H - `pfn_valid()` wrongly approves PFNs with no memmap entry, so `pfn_to_page()` returns a pointer up to tens of megabytes past the end of `mem_map`, and `folio_flush_mapping()`/`flush_aliases()` read and follow that out-of-bounds kernel data as an `address_space`. This is a wide, PFN-indexed out-of-bounds read, far beyond a strictly bounded few bytes.\nI:H - `update_mmu_cache_range()` performs `test_and_set_bit(PG_dcache_clean, \u0026folio-\u003eflags.f)` on the out-of-bounds `struct page`, an attacker-positioned out-of-bounds atomic write into arbitrary kernel memory, and then walks a garbage `address_space`/i_mmap tree. Per the OOB-write guidance this is High.\nA:H - The documented, reproduced impact is a fatal kernel paging fault and panic (\"Unable to handle kernel paging request ... Kernel panic - not syncing: Oops\"), and the corrupted low-memory limits can equally cause the allocator and DMA logic to operate on non-existent DRAM. The condition is triggerable repeatedly at will."
            }
          ]
        }
      ],
      "providerMetadata": {
        "dateUpdated": "2026-08-05T12:08:49.485Z",
        "orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
        "shortName": "Linux"
      },
      "references": [
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          "url": "https://git.kernel.org/stable/c/25f09699edd360b534ccae16bc276c3b52c471f3"
        },
        {
          "url": "https://git.kernel.org/stable/c/5c3e38a367822f036227dd52bac82dc4a05157e2"
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          "url": "https://git.kernel.org/stable/c/b1ec9faef7e36269ca3ec890972a78effbaeb975"
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        },
        {
          "url": "https://git.kernel.org/stable/c/a20b83cf45be2057f3d073506779e52c7fa17f94"
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      ],
      "title": "nios2: ensure that memblock.current_limit is set when setting pfn limits",
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    "assignerShortName": "Linux",
    "cveId": "CVE-2025-40245",
    "datePublished": "2025-12-04T15:31:34.142Z",
    "dateReserved": "2025-04-16T07:20:57.181Z",
    "dateUpdated": "2026-08-05T12:08:49.485Z",
    "state": "PUBLISHED"
  },
  "dataType": "CVE_RECORD",
  "dataVersion": "5.2",
  "vulnerability-lookup:meta": {
    "epss": {
      "cve": "CVE-2025-40245",
      "date": "2026-10-29",
      "epss": "0.00155",
      "percentile": "0.04564"
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    "microsoft_vex": {
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      "cve": "CVE-2025-40245",
      "id": "msrc_CVE-2025-40245",
      "initial_release_date": "2025-12-02T00:00:00.000Z",
      "product_status:known_not_affected": "1",
      "source": "Microsoft CSAF VEX",
      "status": "final",
      "title": "nios2: ensure that memblock.current_limit is set when setting pfn limits",
      "url": "https://msrc.microsoft.com/csaf/vex/2025/msrc_cve-2025-40245.json",
      "version": "3"
    },
    "nvd": {
      "cve": {
        "affected": [
          {
            "affectedData": [
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                "defaultStatus": "unaffected",
                "product": "Linux",
                "programFiles": [
                  "arch/nios2/kernel/setup.c"
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                "vendor": "Linux",
                "versions": [
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                    "versionType": "original_commit_for_fix"
                  }
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            ],
            "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67"
          }
        ],
        "cveTags": [],
        "descriptions": [
          {
            "lang": "en",
            "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nnios2: ensure that memblock.current_limit is set when setting pfn limits\n\nOn nios2, with CONFIG_FLATMEM set, the kernel relies on\nmemblock_get_current_limit() to determine the limits of mem_map, in\nparticular for max_low_pfn.\nUnfortunately, memblock.current_limit is only default initialized to\nMEMBLOCK_ALLOC_ANYWHERE at this point of the bootup, potentially leading\nto situations where max_low_pfn can erroneously exceed the value of\nmax_pfn and, thus, the valid range of available DRAM.\n\nThis can in turn cause kernel-level paging failures, e.g.:\n\n[   76.900000] Unable to handle kernel paging request at virtual address 20303000\n[   76.900000] ea = c0080890, ra = c000462c, cause = 14\n[   76.900000] Kernel panic - not syncing: Oops\n[   76.900000] ---[ end Kernel panic - not syncing: Oops ]---\n\nThis patch fixes this by pre-calculating memblock.current_limit\nbased on the upper limits of the available memory ranges via\nadjust_lowmem_bounds, a simplified version of the equivalent\nimplementation within the arm architecture."
          },
          {
            "lang": "es",
            "value": "En el kernel de Linux, la siguiente vulnerabilidad ha sido resuelta:\n\nnios2: asegurar que memblock.current_limit est\u00e9 configurado al establecer los l\u00edmites de pfn\n\nEn nios2, con CONFIG_FLATMEM configurado, el kernel se basa en memblock_get_current_limit() para determinar los l\u00edmites de mem_map, en particular para max_low_pfn.\nDesafortunadamente, memblock.current_limit solo se inicializa por defecto a MEMBLOCK_ALLOC_ANYWHERE en este punto del arranque, lo que puede llevar a situaciones en las que max_low_pfn puede exceder err\u00f3neamente el valor de max_pfn y, por lo tanto, el rango v\u00e1lido de DRAM disponible.\n\nEsto a su vez puede causar fallos de paginaci\u00f3n a nivel de kernel, por ejemplo:\n\n[   76.900000] Unable to handle kernel paging request at virtual address 20303000\n[   76.900000] ea = c0080890, ra = c000462c, cause = 14\n[   76.900000] Kernel panic - not syncing: Oops\n[   76.900000] ---[ end Kernel panic - not syncing: Oops ]---\n\nEste parche soluciona esto precalculando memblock.current_limit bas\u00e1ndose en los l\u00edmites superiores de los rangos de memoria disponibles a trav\u00e9s de adjust_lowmem_bounds, una versi\u00f3n simplificada de la implementaci\u00f3n equivalente dentro de la arquitectura arm."
          }
        ],
        "id": "CVE-2025-40245",
        "lastModified": "2026-10-19T19:10:00.130",
        "metrics": {
          "cvssMetricV31": [
            {
              "cvssData": {
                "attackComplexity": "LOW",
                "attackVector": "LOCAL",
                "availabilityImpact": "HIGH",
                "baseScore": 7.8,
                "baseSeverity": "HIGH",
                "confidentialityImpact": "HIGH",
                "integrityImpact": "HIGH",
                "privilegesRequired": "LOW",
                "scope": "UNCHANGED",
                "userInteraction": "NONE",
                "vectorString": "CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H",
                "version": "3.1"
              },
              "exploitabilityScore": 1.8,
              "impactScore": 5.9,
              "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
              "type": "Secondary"
            }
          ]
        },
        "published": "2025-12-04T16:16:17.827",
        "references": [
          {
            "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
            "url": "https://git.kernel.org/stable/c/25f09699edd360b534ccae16bc276c3b52c471f3"
          },
          {
            "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
            "url": "https://git.kernel.org/stable/c/5c3e38a367822f036227dd52bac82dc4a05157e2"
          },
          {
            "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
            "url": "https://git.kernel.org/stable/c/8912814f14e298b83df072fecc1f7ed1b63b1b2c"
          },
          {
            "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
            "url": "https://git.kernel.org/stable/c/90f5f715550e07cd6a51f80fc3f062d832c8c997"
          },
          {
            "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
            "url": "https://git.kernel.org/stable/c/a20b83cf45be2057f3d073506779e52c7fa17f94"
          },
          {
            "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
            "url": "https://git.kernel.org/stable/c/b1ec9faef7e36269ca3ec890972a78effbaeb975"
          }
        ],
        "sourceIdentifier": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
        "vulnStatus": "Deferred"
      }
    },
    "redhat_vex": {
      "aggregate_severity": "None",
      "current_release_date": "2026-10-30T08:04:30+00:00",
      "cve": "CVE-2025-40245",
      "id": "CVE-2025-40245",
      "initial_release_date": "2025-12-04T00:00:00+00:00",
      "product_status:known_not_affected": "276",
      "source": "Red Hat CSAF VEX",
      "status": "final",
      "title": "kernel: nios2: ensure that memblock.current_limit is set when setting pfn limits",
      "url": "https://security.access.redhat.com/data/csaf/v2/vex/2025/cve-2025-40245.json",
      "version": "3"
    }
  }
}



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Tags
Taxonomy of the tags.




Drag nodes to arrange them. Double-click a related vulnerability to open it, or a source to visit its link. The Physics button on the left tunes the layout and the simulation; the legend at the bottom left hides or shows nodes by kind and by sighting type.

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

Author Source Type Date Other

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.
Vulnerability timeline

Sightings and recorded dates, grouped by day · UTC

JSON

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    Related by attack behaviour

    Vulnerabilities whose description is nearest to this one in the vector space of the CIRCL/vulnerability-attack-technique-biencoder model. This is a similarity search over the bi-encoder space (plain cosine), not a classification, and it has no measured accuracy.