CVE-2020-26242: Github.com/ethereum/go ethereum Denial of Service Vulnerability

{
  "schema_version" : "1.4.0",
  "id" : "GHSA-jm5c-rv3w-w83m",
  "modified" : "2025-01-30T14:38:53Z",
  "published" : "2021-06-29T21:13:20Z",
  "aliases" : [ "CVE-2020-26242" ],
  "summary" : "Denial of service in geth",
  "details" : "### Impact\nDenial-of-service (crash) during block processing\n\n### Details\n\nAffected versions suffer from a vulnerability which can be exploited through the `MULMOD` operation, by specifying a modulo of `0`: `mulmod(a,b,0)`, causing a `panic` in the underlying library. \nThe crash was in the `uint256` library, where a buffer [underflowed](https://github.com/holiman/uint256/blob/4ce82e695c10ddad57215bdbeafb68b8c5df2c30/uint256.go#L442).\n\n\tif `d == 0`, `dLen` remains `0`\n\nand https://github.com/holiman/uint256/blob/4ce82e695c10ddad57215bdbeafb68b8c5df2c30/uint256.go#L451 will try to access index `[-1]`.\n\nThe `uint256` library was first merged in this [commit](https://github.com/ethereum/go-ethereum/commit/cf6674539c589f80031f3371a71c6a80addbe454), on 2020-06-08. \nExploiting this vulnerabilty would cause all vulnerable nodes to drop off the network. \n\nThe issue was brought to our attention through a [bug report](https://github.com/ethereum/go-ethereum/issues/21367), showing a `panic` occurring on sync from genesis on the Ropsten network.\n \nIt was estimated that the least obvious way to fix this would be to merge the fix into `uint256`, make a new release of that library and then update the geth-dependency.\n\n- https://github.com/holiman/uint256/releases/tag/v1.1.1 was made the same day, \n- PR to address the issue: https://github.com/holiman/uint256/pull/80 \n- PR to update geth deps: https://github.com/ethereum/go-ethereum/pull/21368 \n\n\n\n### Patches\n\nUpgrade to v1.9.18 or higher\n\n### Workarounds\n\nNot at this time\n\n### References\n\nhttps://blog.ethereum.org/2020/11/12/geth_security_release/\n### For more information\nIf you have any questions or comments about this advisory:\n* Open an issue in [go-ethereum](https://github.com/ethereum/go-ethereum)\n* Email us at [security@ethereum.org](mailto:security@ethereum.org)\n",
  "severity" : [ {
    "type" : "CVSS_V3",
    "score" : "CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H"
  } ],
  "affected" : [ {
    "package" : {
      "ecosystem" : "Go",
      "name" : "github.com/ethereum/go-ethereum"
    },
    "ranges" : [ {
      "type" : "ECOSYSTEM",
      "events" : [ {
        "introduced" : "1.9.16"
      }, {
        "fixed" : "1.9.18"
      } ]
    } ]
  }, {
    "package" : {
      "ecosystem" : "Go",
      "name" : "github.com/holiman/uint256"
    },
    "ranges" : [ {
      "type" : "ECOSYSTEM",
      "events" : [ {
        "introduced" : "0.1.0"
      }, {
        "fixed" : "1.1.1"
      } ]
    } ]
  } ],
  "references" : [ {
    "type" : "WEB",
    "url" : "https://github.com/ethereum/go-ethereum/security/advisories/GHSA-jm5c-rv3w-w83m"
  }, {
    "type" : "ADVISORY",
    "url" : "https://nvd.nist.gov/vuln/detail/CVE-2020-26242"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/holiman/uint256/pull/80"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/ethereum/go-ethereum/commit/7163a6664ee664df81b9028ab3ba13b9d65a7196"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/holiman/uint256/commit/6785da6e3eea403260a5760029e722aa4ff1716d"
  }, {
    "type" : "WEB",
    "url" : "https://blog.ethereum.org/2020/11/12/geth_security_release"
  }, {
    "type" : "PACKAGE",
    "url" : "https://github.com/ethereum/go-ethereum"
  }, {
    "type" : "WEB",
    "url" : "https://pkg.go.dev/vuln/GO-2021-0103"
  } ],
  "database_specific" : {
    "cwe_ids" : [ "CWE-125", "CWE-191", "CWE-400" ],
    "severity" : "MODERATE",
    "github_reviewed" : true,
    "github_reviewed_at" : "2021-05-21T21:50:44Z",
    "nvd_published_at" : null
  }
}