CVE-2026-68278 (GCVE-0-2026-68278)
Vulnerability from cvelistv5
Published
2026-08-10 12:01
Modified
2026-08-23 12:46
Severity ?
Summary
In the Linux kernel, the following vulnerability has been resolved: drm/dp/mst: fix buffer overflows in sideband chunk accumulation drm_dp_sideband_append_payload() has three related bugs when processing device-provided sideband reply data: 1. Zero-length curchunk_len underflow: msg_len is a 6-bit field taken directly from the DP sideband header. If a device sends msg_len=0, curchunk_len is set to zero. The condition (curchunk_idx >= curchunk_len) is immediately true, and curchunk_len-1 wraps to 255 (u8 underflow). drm_dp_msg_data_crc4() reads 255 bytes from chunk[48], then memcpy() writes 255 bytes into msg[], both far out of bounds. 2. chunk[48] overflow: curchunk_len can reach 63 (6-bit field). chunk[] is only 48 bytes. Multi-iteration payload assembly appends 16-byte blocks until curchunk_idx reaches curchunk_len, writing up to 15 bytes past the end of chunk[] into msg[]. 3. msg[256] overflow: each chunk contributes (curchunk_len-1) bytes to msg[]. No check ensures curlen + (curchunk_len-1) stays within msg[256], so the memcpy can spill into adjacent struct fields. All three are reachable from any DP MST device that can forge sideband reply messages on a physical connection.
References
Impacted products
Vendor Product Version
Linux Linux Version: ad7f8a1f9ced7f049f9b66d588723f243a7034cd
Version: ad7f8a1f9ced7f049f9b66d588723f243a7034cd
Version: ad7f8a1f9ced7f049f9b66d588723f243a7034cd
Version: ad7f8a1f9ced7f049f9b66d588723f243a7034cd
Version: ad7f8a1f9ced7f049f9b66d588723f243a7034cd
Version: ad7f8a1f9ced7f049f9b66d588723f243a7034cd
Version: ad7f8a1f9ced7f049f9b66d588723f243a7034cd
Version: ad7f8a1f9ced7f049f9b66d588723f243a7034cd
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{
  "containers": {
    "cna": {
      "affected": [
        {
          "defaultStatus": "unaffected",
          "product": "Linux",
          "programFiles": [
            "drivers/gpu/drm/display/drm_dp_mst_topology.c"
          ],
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          "vendor": "Linux",
          "versions": [
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              "version": "3.17"
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              "version": "0",
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              "version": "5.10.266",
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              "version": "5.15.217",
              "versionType": "semver"
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              "version": "6.1.183",
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              "version": "7.2",
              "versionType": "original_commit_for_fix"
            }
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        }
      ],
      "cpeApplicability": [
        {
          "nodes": [
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              ],
              "negate": false,
              "operator": "OR"
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        }
      ],
      "descriptions": [
        {
          "lang": "en",
          "value": "In the Linux kernel, the following vulnerability has been resolved:\n\ndrm/dp/mst: fix buffer overflows in sideband chunk accumulation\n\ndrm_dp_sideband_append_payload() has three related bugs when processing\ndevice-provided sideband reply data:\n\n1. Zero-length curchunk_len underflow: msg_len is a 6-bit field taken\n   directly from the DP sideband header. If a device sends msg_len=0,\n   curchunk_len is set to zero. The condition (curchunk_idx \u003e= curchunk_len)\n   is immediately true, and curchunk_len-1 wraps to 255 (u8 underflow).\n   drm_dp_msg_data_crc4() reads 255 bytes from chunk[48], then memcpy()\n   writes 255 bytes into msg[], both far out of bounds.\n\n2. chunk[48] overflow: curchunk_len can reach 63 (6-bit field). chunk[] is\n   only 48 bytes. Multi-iteration payload assembly appends 16-byte blocks\n   until curchunk_idx reaches curchunk_len, writing up to 15 bytes past\n   the end of chunk[] into msg[].\n\n3. msg[256] overflow: each chunk contributes (curchunk_len-1) bytes to\n   msg[]. No check ensures curlen + (curchunk_len-1) stays within msg[256],\n   so the memcpy can spill into adjacent struct fields.\n\nAll three are reachable from any DP MST device that can forge sideband\nreply messages on a physical connection."
        }
      ],
      "providerMetadata": {
        "dateUpdated": "2026-08-23T12:46:15.450Z",
        "orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
        "shortName": "Linux"
      },
      "references": [
        {
          "url": "https://git.kernel.org/stable/c/ef2ecb6cf268debf3890df99fea01b6452dcf78e"
        },
        {
          "url": "https://git.kernel.org/stable/c/d4e05dedb252ed3e540a0c9be511e427f098110a"
        },
        {
          "url": "https://git.kernel.org/stable/c/4d5109075a787de28c9e89940f9dee45269f91fa"
        },
        {
          "url": "https://git.kernel.org/stable/c/53937a2787d29c7a460e984dc4f20ff6ac91dc65"
        },
        {
          "url": "https://git.kernel.org/stable/c/ef0dbcc200c3389f1f781ab181932a97e54b51af"
        },
        {
          "url": "https://git.kernel.org/stable/c/1e5827839ad0ceb0079d1560c321fa3656b54f21"
        },
        {
          "url": "https://git.kernel.org/stable/c/a6366b551079c79bf7bdbadd74c97358bcfe2d58"
        },
        {
          "url": "https://git.kernel.org/stable/c/55bd5e685bda455b9b50c835f8c8442d52a344a3"
        }
      ],
      "title": "drm/dp/mst: fix buffer overflows in sideband chunk accumulation",
      "x_generator": {
        "engine": "bippy-1.2.0"
      }
    }
  },
  "cveMetadata": {
    "assignerOrgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
    "assignerShortName": "Linux",
    "cveId": "CVE-2026-68278",
    "datePublished": "2026-08-10T12:01:54.285Z",
    "dateReserved": "2026-07-30T09:28:09.379Z",
    "dateUpdated": "2026-08-23T12:46:15.450Z",
    "state": "PUBLISHED"
  },
  "dataType": "CVE_RECORD",
  "dataVersion": "5.2"
}


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