CVE-2026-74449 (GCVE-0-2026-74449)

Vulnerability from cvelistv5 – Published: 2026-08-15 12:26 – Updated: 2026-08-18 06:56
VLAI
Title
drm/amd/display: Fix divide-by-zero in calculate_mcache_setting on zero viewport
Summary
In the Linux kernel, the following vulnerability has been resolved: drm/amd/display: Fix divide-by-zero in calculate_mcache_setting on zero viewport If a plane reaches calculate_mcache_setting with a zero-area viewport, calculate_mcache_setting exits early with num_mcaches == 0 and mvmpg_width/height == 0. This will cause a divide-by-zero panic and can also cause an underflow on num_mcaches. Fix this by changing calculate_mcache_setting to bool and adding guards after each calculate_mcache_row_bytes call. If num_mcaches or mvmpg_width/height is zero, return a false. Callers will propagate the failure as a rejected mode, which prevents the panic. (cherry picked from commit 29c0f7c655f47bcbd575ff75e58480df6ec3c9da)
Severity
7.8 (High)
CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
Assigner
References
Impacted products
Vendor Product Version CPE status
Linux Linux Affected: 70839da6360500a82e4d5f78499284474cbed7c1 , < 1f93537881fd22712732a60ad12572a3fd40c0ec (git)
Affected: 70839da6360500a82e4d5f78499284474cbed7c1 , < f327e389c07cfc3a2f6ff54f6214e1a52d457edc (git)
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Linux Linux Affected: 6.11
Unaffected: 0 , < 6.11 (semver)
Unaffected: 7.1.8 , ≤ 7.1.* (semver)
Unaffected: 7.2 , ≤ * (original_commit_for_fix)
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{
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        {
          "defaultStatus": "unaffected",
          "product": "Linux",
          "programFiles": [
            "drivers/gpu/drm/amd/display/dc/dml2_0/dml21/src/dml2_core/dml2_core_dcn4_calcs.c"
          ],
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          "value": "In the Linux kernel, the following vulnerability has been resolved:\n\ndrm/amd/display: Fix divide-by-zero in calculate_mcache_setting on zero viewport\n\nIf a plane reaches calculate_mcache_setting with a zero-area viewport,\ncalculate_mcache_setting exits early with num_mcaches == 0 and\nmvmpg_width/height == 0. This will cause a divide-by-zero panic and can\nalso cause an underflow on num_mcaches.\n\nFix this by changing calculate_mcache_setting to bool and adding guards\nafter each calculate_mcache_row_bytes call. If num_mcaches or\nmvmpg_width/height is zero, return a false. Callers will propagate the\nfailure as a rejected mode, which prevents the panic.\n\n(cherry picked from commit 29c0f7c655f47bcbd575ff75e58480df6ec3c9da)"
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            "baseSeverity": "HIGH",
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            "version": "3.1"
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              "lang": "en",
              "value": "AV:L - The bug is reached during DRM atomic display validation on AMDGPU DCN4.x (dml21 path): userspace ioctl \u2192 amdgpu_dm atomic commit \u2192 dc_validate_global_state/dc_validate_with_context \u2192 dcn401/dcn42_validate_bandwidth \u2192 dml2_validate \u2192 dml21_validate \u2192 dml2_check_mode_supported \u2192 dml2_core_calcs_mode_support_ex \u2192 calculate_mcache_setting; no network or physical bus is involved.\nAC:L - An attacker with DRM card access can submit atomic commits that configure DCC-enabled planes and repeatedly probe scaler/viewport edge cases (including degenerate zero-area viewports or zero mvmpg dimensions) to reach calculate_mcache_setting; once triggered, num_mcaches==0 deterministically underflows loop bounds and causes divide-by-zero without races or uncontrollable heap layout.\nPR:L - Exploitation requires only standard local DRM display privileges to perform atomic modeset ioctl on /dev/dri/card* (typical for session-owning desktop users in the video/render group), not init-namespace root/CAP_SYS_ADMIN; user namespaces do not grant independent access to the host GPU display stack.\nUI:N - No victim interaction is required beyond the attacker issuing their own DRM atomic commit to configure a plane with DCC compression enabled; the kernel panic/corruption occurs during in-kernel DML bandwidth validation, not from another user opening files or mounting filesystems.\nS:U - The vulnerability corrupts kernel memory and can enable local privilege escalation within the same host kernel running the AMDGPU display driver; it does not cross a VM, IOMMU, or sandbox boundary such as KVM guest-to-host escape.\nC:H - When num_mcaches is zero, unsigned underflow in loop bounds (n \u003c *num_mcaches_l - 1) and indexing (mcache_offsets_l[*num_mcaches_l - 1]) performs massive out-of-bounds reads/writes past the fixed-size mcache_offsets arrays in kernel DML state, enabling disclosure of adjacent kernel heap memory rather than a pure crash with no data exposure.\nI:H - The same num_mcaches underflow drives unbounded out-of-bounds writes into mode_lib mcache offset arrays and related DML structures during calculate_mcache_setting, providing attacker-influenced kernel memory corruption primitives that could be leveraged for control-flow hijacking beyond a simple denial-of-service fault.\nA:H - The vulnerable path performs integer divide-by-zero on zero mvmpg_access_width/num_mcaches and executes out-of-bounds mcache offset writes, either of which can immediately trigger a kernel oops or panic during display mode validation, denying service to all users on affected AMD DCN4.x systems until reboot."
            }
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        "dateUpdated": "2026-08-18T06:56:35.806Z",
        "orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
        "shortName": "Linux"
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          "url": "https://git.kernel.org/stable/c/1f93537881fd22712732a60ad12572a3fd40c0ec"
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          "url": "https://git.kernel.org/stable/c/f327e389c07cfc3a2f6ff54f6214e1a52d457edc"
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      "title": "drm/amd/display: Fix divide-by-zero in calculate_mcache_setting on zero viewport",
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    "assignerShortName": "Linux",
    "cveId": "CVE-2026-74449",
    "datePublished": "2026-08-15T12:26:54.519Z",
    "dateReserved": "2026-08-15T05:44:03.899Z",
    "dateUpdated": "2026-08-18T06:56:35.806Z",
    "state": "PUBLISHED"
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    "redhat_vex": {
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      "current_release_date": "2026-08-21T11:32:47+00:00",
      "cve": "CVE-2026-74449",
      "id": "CVE-2026-74449",
      "initial_release_date": "2026-08-15T00:00:00+00:00",
      "product_status:known_affected": "274",
      "source": "Red Hat CSAF VEX",
      "status": "final",
      "title": "kernel: drm/amd/display: Fix divide-by-zero in calculate_mcache_setting on zero viewport",
      "url": "https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-74449.json",
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      "cve": "CVE-2026-74449",
      "id": "CVE-2026-74449",
      "initial_release_date": "2026-08-15T23:52:50Z",
      "source": "SUSE CSAF VEX",
      "status": "interim",
      "title": "SUSE CVE CVE-2026-74449",
      "url": "https://ftp.suse.com/pub/projects/security/csaf-vex/cve-2026-74449.json",
      "version": "3"
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}



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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.

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  • 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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