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ubifs: fix out-of-bounds read in signature length check

Type: advisorySource: Official CVE List1 source record

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.

Announced Group revision 1
Original source ↗

CVE-2026-89720

Primary source · Revision 1

Imported from structured advisory data. Source references identify upstream records or fields; verify affected versions and your deployed configuration.

Security context

Source reference: cve:CVE-2026-89720

Linux

Source reference: /containers/cna/affected/0/product

Affected versions
Not stated in this record
Fixed versions
Not stated in this record
Prerequisites
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Linux

Source reference: /containers/cna/affected/1/product

Affected versions
Not stated in this record
Fixed versions
Not stated in this record
Prerequisites
Not stated in this record

Structured affected-version data

Original package identities and version rules from this source.

[
  {
    "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
    "vendor": "Linux",
    "product": "Linux",
    "versions": [
      {
        "status": "affected",
        "version": "817aa094842dfc3a6b98c9582d4a647827f66201",
        "lessThan": "ab7405bd86331cc2dbc8201699d4adc33bea75e7",
        "versionType": "git"
      },
      {
        "status": "affected",
        "version": "817aa094842dfc3a6b98c9582d4a647827f66201",
        "lessThan": "11abc34698cb3172badf8aa12e623f1bac98bbd8",
        "versionType": "git"
      },
      {
        "status": "affected",
        "version": "817aa094842dfc3a6b98c9582d4a647827f66201",
        "lessThan": "8cc3da72cf57acb4b77442ea8cec48425dff7c06",
        "versionType": "git"
      },
      {
        "status": "affected",
        "version": "817aa094842dfc3a6b98c9582d4a647827f66201",
        "lessThan": "37a9d25a563f5f9103282954ce573c4a61321e7c",
        "versionType": "git"
      },
      {
        "status": "affected",
        "version": "817aa094842dfc3a6b98c9582d4a647827f66201",
        "lessThan": "f76b79d6e42af20682495bccd22f72c7164b0018",
        "versionType": "git"
      },
      {
        "status": "affected",
        "version": "817aa094842dfc3a6b98c9582d4a647827f66201",
        "lessThan": "a1dc246f98bb94233effa4fa3ec7bf84700bb7d1",
        "versionType": "git"
      },
      {
        "status": "affected",
        "version": "817aa094842dfc3a6b98c9582d4a647827f66201",
        "lessThan": "83e1aa9f5f906c9b1f4949d0521f0f950a159d96",
        "versionType": "git"
      },
      {
        "status": "affected",
        "version": "817aa094842dfc3a6b98c9582d4a647827f66201",
        "lessThan": "95d27c1708bb6e8823c8e7c623f9abc2a91bf4bf",
        "versionType": "git"
      }
    ],
    "programFiles": [
      "fs/ubifs/auth.c"
    ],
    "defaultStatus": "unaffected"
  },
  {
    "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
    "vendor": "Linux",
    "product": "Linux",
    "versions": [
      {
        "status": "affected",
        "version": "5.3"
      },
      {
        "status": "unaffected",
        "version": "0",
        "lessThan": "5.3",
        "versionType": "semver"
      },
      {
        "status": "unaffected",
        "version": "5.10.270",
        "versionType": "semver",
        "lessThanOrEqual": "5.10.*"
      },
      {
        "status": "unaffected",
        "version": "5.15.221",
        "versionType": "semver",
        "lessThanOrEqual": "5.15.*"
      },
      {
        "status": "unaffected",
        "version": "6.1.188",
        "versionType": "semver",
        "lessThanOrEqual": "6.1.*"
      },
      {
        "status": "unaffected",
        "version": "6.6.157",
        "versionType": "semver",
        "lessThanOrEqual": "6.6.*"
      },
      {
        "status": "unaffected",
        "version": "6.12.109",
        "versionType": "semver",
        "lessThanOrEqual": "6.12.*"
      },
      {
        "status": "unaffected",
        "version": "6.18.50",
        "versionType": "semver",
        "lessThanOrEqual": "6.18.*"
      },
      {
        "status": "unaffected",
        "version": "7.2.4",
        "versionType": "semver",
        "lessThanOrEqual": "7.2.*"
      },
      {
        "status": "unaffected",
        "version": "7.3",
        "versionType": "original_commit_for_fix",
        "lessThanOrEqual": "*"
      }
    ],
    "programFiles": [
      "fs/ubifs/auth.c"
    ],
    "defaultStatus": "affected"
  }
]
Related CVEs
CVE-2026-89720

Source reference: /cveMetadata/cveId

Publisher severity

high

Source reference: /containers/cna/metrics

Event
#35197 · Revision 1
Added to Heist Feed
Publisher date
Read the original announcement

Revision history

  1. CVE-2026-89720 · Revision 1Source updated