FKIE_CVE-2026-89720

Vulnerability from fkie_nvd - Published: 2026-09-11 20:20 - Updated: 2026-10-19 09:18
Severity
7.7 (High) - CVSS:3.1/AV:L/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:H
Summary
In the Linux kernel, the following vulnerability has been resolved: ubifs: fix out-of-bounds read in signature length check ubifs_sb_verify_signature() bounds the on-disk ubifs_sig_node->len field before handing the signature payload to verify_pkcs7_signature(), but the check has the wrong sign: if (le32_to_cpu(signode->len) > snod->len + sizeof(struct ubifs_sig_node)) The signature bytes start sizeof(struct ubifs_sig_node) (UBIFS_SIG_NODE_SZ, 64 bytes) into the node, so the payload is at most snod->len - sizeof(struct ubifs_sig_node) bytes long. Adding the header size instead of subtracting it accepts a declared length up to 2 * UBIFS_SIG_NODE_SZ larger than the node actually holds -- past the end of c->sbuf, which is vmalloc(c->leb_size). verify_pkcs7_signature() -> pkcs7_parse_message() -> asn1_ber_decoder() is then handed that inflated length and reads beyond the allocation while walking the DER headers. The node length comes straight from the mounted image, so a crafted signed UBIFS image reaches this via ubifs_read_superblock() before the signature is cryptographically checked. snod->len is guaranteed to be >= UBIFS_SIG_NODE_SZ by the node scanner (c->ranges[UBIFS_SIG_NODE].min_len == UBIFS_SIG_NODE_SZ), so the corrected subtraction cannot underflow. Legitimately signed images are unaffected: a correct superblock never declares a signature longer than the node it is embedded in.
References
416baaa9-dc9f-4396-8d5f-8c081fb06d67https://git.kernel.org/stable/c/11abc34698cb3172badf8aa12e623f1bac98bbd8
416baaa9-dc9f-4396-8d5f-8c081fb06d67https://git.kernel.org/stable/c/37a9d25a563f5f9103282954ce573c4a61321e7c
416baaa9-dc9f-4396-8d5f-8c081fb06d67https://git.kernel.org/stable/c/83e1aa9f5f906c9b1f4949d0521f0f950a159d96
416baaa9-dc9f-4396-8d5f-8c081fb06d67https://git.kernel.org/stable/c/8cc3da72cf57acb4b77442ea8cec48425dff7c06
416baaa9-dc9f-4396-8d5f-8c081fb06d67https://git.kernel.org/stable/c/95d27c1708bb6e8823c8e7c623f9abc2a91bf4bf
416baaa9-dc9f-4396-8d5f-8c081fb06d67https://git.kernel.org/stable/c/a1dc246f98bb94233effa4fa3ec7bf84700bb7d1
416baaa9-dc9f-4396-8d5f-8c081fb06d67https://git.kernel.org/stable/c/ab7405bd86331cc2dbc8201699d4adc33bea75e7
416baaa9-dc9f-4396-8d5f-8c081fb06d67https://git.kernel.org/stable/c/f76b79d6e42af20682495bccd22f72c7164b0018
Impacted products
Vendor Product Version
To clipboard 

{
  "affected": [
    {
      "affectedData": [
        {
          "defaultStatus": "unaffected",
          "product": "Linux",
          "programFiles": [
            "fs/ubifs/auth.c"
          ],
          "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
          "vendor": "Linux",
          "versions": [
            {
              "lessThan": "ab7405bd86331cc2dbc8201699d4adc33bea75e7",
              "status": "affected",
              "version": "817aa094842dfc3a6b98c9582d4a647827f66201",
              "versionType": "git"
            },
            {
              "lessThan": "11abc34698cb3172badf8aa12e623f1bac98bbd8",
              "status": "affected",
              "version": "817aa094842dfc3a6b98c9582d4a647827f66201",
              "versionType": "git"
            },
            {
              "lessThan": "8cc3da72cf57acb4b77442ea8cec48425dff7c06",
              "status": "affected",
              "version": "817aa094842dfc3a6b98c9582d4a647827f66201",
              "versionType": "git"
            },
            {
              "lessThan": "37a9d25a563f5f9103282954ce573c4a61321e7c",
              "status": "affected",
              "version": "817aa094842dfc3a6b98c9582d4a647827f66201",
              "versionType": "git"
            },
            {
              "lessThan": "f76b79d6e42af20682495bccd22f72c7164b0018",
              "status": "affected",
              "version": "817aa094842dfc3a6b98c9582d4a647827f66201",
              "versionType": "git"
            },
            {
              "lessThan": "a1dc246f98bb94233effa4fa3ec7bf84700bb7d1",
              "status": "affected",
              "version": "817aa094842dfc3a6b98c9582d4a647827f66201",
              "versionType": "git"
            },
            {
              "lessThan": "83e1aa9f5f906c9b1f4949d0521f0f950a159d96",
              "status": "affected",
              "version": "817aa094842dfc3a6b98c9582d4a647827f66201",
              "versionType": "git"
            },
            {
              "lessThan": "95d27c1708bb6e8823c8e7c623f9abc2a91bf4bf",
              "status": "affected",
              "version": "817aa094842dfc3a6b98c9582d4a647827f66201",
              "versionType": "git"
            }
          ]
        },
        {
          "defaultStatus": "affected",
          "product": "Linux",
          "programFiles": [
            "fs/ubifs/auth.c"
          ],
          "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
          "vendor": "Linux",
          "versions": [
            {
              "status": "affected",
              "version": "5.3"
            },
            {
              "lessThan": "5.3",
              "status": "unaffected",
              "version": "0",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "5.10.*",
              "status": "unaffected",
              "version": "5.10.270",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "5.15.*",
              "status": "unaffected",
              "version": "5.15.221",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "6.1.*",
              "status": "unaffected",
              "version": "6.1.188",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "6.6.*",
              "status": "unaffected",
              "version": "6.6.157",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "6.12.*",
              "status": "unaffected",
              "version": "6.12.109",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "6.18.*",
              "status": "unaffected",
              "version": "6.18.50",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "7.2.*",
              "status": "unaffected",
              "version": "7.2.4",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "*",
              "status": "unaffected",
              "version": "7.3",
              "versionType": "original_commit_for_fix"
            }
          ]
        }
      ],
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67"
    }
  ],
  "cveTags": [],
  "descriptions": [
    {
      "lang": "en",
      "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nubifs: fix out-of-bounds read in signature length check\n\nubifs_sb_verify_signature() bounds the on-disk ubifs_sig_node-\u003elen field\nbefore handing the signature payload to verify_pkcs7_signature(), but the\ncheck has the wrong sign:\n\n\tif (le32_to_cpu(signode-\u003elen) \u003e snod-\u003elen + sizeof(struct ubifs_sig_node))\n\nThe signature bytes start sizeof(struct ubifs_sig_node) (UBIFS_SIG_NODE_SZ,\n64 bytes) into the node, so the payload is at most\n\n\tsnod-\u003elen - sizeof(struct ubifs_sig_node)\n\nbytes long. Adding the header size instead of subtracting it accepts a\ndeclared length up to 2 * UBIFS_SIG_NODE_SZ larger than the node actually\nholds -- past the end of c-\u003esbuf, which is vmalloc(c-\u003eleb_size).\nverify_pkcs7_signature() -\u003e pkcs7_parse_message() -\u003e asn1_ber_decoder()\nis then handed that inflated length and reads beyond the allocation while\nwalking the DER headers. The node length comes straight from the mounted\nimage, so a crafted signed UBIFS image reaches this via\nubifs_read_superblock() before the signature is cryptographically checked.\n\nsnod-\u003elen is guaranteed to be \u003e= UBIFS_SIG_NODE_SZ by the node scanner\n(c-\u003eranges[UBIFS_SIG_NODE].min_len == UBIFS_SIG_NODE_SZ), so the corrected\nsubtraction cannot underflow. Legitimately signed images are unaffected: a\ncorrect superblock never declares a signature longer than the node it is\nembedded in."
    }
  ],
  "id": "CVE-2026-89720",
  "lastModified": "2026-10-19T09:18:12.130",
  "metrics": {
    "cvssMetricV31": [
      {
        "cvssData": {
          "attackComplexity": "LOW",
          "attackVector": "LOCAL",
          "availabilityImpact": "HIGH",
          "baseScore": 7.7,
          "baseSeverity": "HIGH",
          "confidentialityImpact": "HIGH",
          "integrityImpact": "NONE",
          "privilegesRequired": "NONE",
          "scope": "UNCHANGED",
          "userInteraction": "NONE",
          "vectorString": "CVSS:3.1/AV:L/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:H",
          "version": "3.1"
        },
        "exploitabilityScore": 2.5,
        "impactScore": 5.2,
        "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
        "type": "Secondary"
      }
    ]
  },
  "published": "2026-09-11T20:20:00.943",
  "references": [
    {
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
      "url": "https://git.kernel.org/stable/c/11abc34698cb3172badf8aa12e623f1bac98bbd8"
    },
    {
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
      "url": "https://git.kernel.org/stable/c/37a9d25a563f5f9103282954ce573c4a61321e7c"
    },
    {
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
      "url": "https://git.kernel.org/stable/c/83e1aa9f5f906c9b1f4949d0521f0f950a159d96"
    },
    {
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
      "url": "https://git.kernel.org/stable/c/8cc3da72cf57acb4b77442ea8cec48425dff7c06"
    },
    {
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
      "url": "https://git.kernel.org/stable/c/95d27c1708bb6e8823c8e7c623f9abc2a91bf4bf"
    },
    {
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
      "url": "https://git.kernel.org/stable/c/a1dc246f98bb94233effa4fa3ec7bf84700bb7d1"
    },
    {
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
      "url": "https://git.kernel.org/stable/c/ab7405bd86331cc2dbc8201699d4adc33bea75e7"
    },
    {
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
      "url": "https://git.kernel.org/stable/c/f76b79d6e42af20682495bccd22f72c7164b0018"
    }
  ],
  "sourceIdentifier": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
  "vulnStatus": "Received"
}



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