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Large RSA keys can cause high CPU usage in crypto/tls

Type: advisorySources: OSV

Extremely large RSA keys in certificate chains can cause a client/server to expend significant CPU time verifying signatures. With fix, the size of RSA keys transmitted during handshakes is restricted to <= 8192 bits. Based on a survey of publicly trusted RSA keys, there are currently only three certificates in circulation with keys larger than this, and all three appear to be test certificates that are not actively deployed. It is possible there are larger keys in use in private PKIs, but we target the web PKI, so causing breakage here in the interests of increasing the default safety of users of crypto/tls seems reasonable.

Products
Not specified
Affected versions
Not specified
Fixed versions
Not specified
CVEs
CVE-2023-29409
Confirmed fixed CVEs
Not specified
Updated in this feed
3 Nov 2026, 19:29 UTC · Revision 1

Source evidence

Large RSA keys can cause high CPU usage in crypto/tls

core-osv · Original source

Published 2 Aug 2023, 19:47 UTC

Extremely large RSA keys in certificate chains can cause a client/server to expend significant CPU time verifying signatures. With fix, the size of RSA keys transmitted during handshakes is restricted to <= 8192 bits. Based on a survey of publicly trusted RSA keys, there are currently only three certificates in circulation with keys larger than this, and all three appear to be test certificates that are not actively deployed. It is possible there are larger keys in use in private PKIs, but we target the web PKI, so causing breakage here in the interests of increasing the default safety of users of crypto/tls seems reasonable.

osv:CVE-2023-29409
Complete source record
{
  "id": "d5411efad2905fb0a4d0a9c5fba1cae5892bb1f7d63b2da529f1e1ee0490cd50",
  "url": "https://osv.dev/vulnerability/CVE-2023-29409",
  "method": "structured",
  "payload": {
    "kind": "advisory",
    "title": "Large RSA keys can cause high CPU usage in crypto/tls",
    "summary": "Extremely large RSA keys in certificate chains can cause a client/server to expend significant CPU time verifying signatures. With fix, the size of RSA keys transmitted during handshakes is restricted to <= 8192 bits. Based on a survey of publicly trusted RSA keys, there are currently only three certificates in circulation with keys larger than this, and all three appear to be test certificates that are not actively deployed. It is possible there are larger keys in use in private PKIs, but we target the web PKI, so causing breakage here in the interests of increasing the default safety of users of crypto/tls seems reasonable.",
    "evidence": "osv:CVE-2023-29409",
    "products": [],
    "severity": "unknown",
    "structured": {
      "id": "CVE-2023-29409",
      "aliases": [
        "BIT-golang-2023-29409",
        "CVE-2023-29409",
        "GO-2023-1987"
      ],
      "affected": [
        {
          "ranges": [
            {
              "repo": "https://github.com/golang/go",
              "type": "GIT",
              "events": [
                {
                  "introduced": "0"
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                {
                  "fixed": "0ae54ddd37302bdd2a8c775135bf5f076a18eeb3"
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              "database_specific": {
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                    "source": "CPE_RANGE"
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                  {
                    "cpe": "cpe:2.3:a:golang:go:*:*:*:*:*:*:*:*",
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                        "introduced": "1.20.0"
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                    "source": "CPE_RANGE"
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          "versions": [
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          "database_specific": {
            "source": "https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2023-29409.json"
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      ],
      "modified": "2026-10-28T02:30:31.678500792Z",
      "provider": "osv",
      "references": [
        "https://go.dev/cl/515257",
        "https://go.dev/issue/61460",
        "https://groups.google.com/g/golang-announce/c/X0b6CsSAaYI/m/Efv5DbZ9AwAJ",
        "https://pkg.go.dev",
        "https://pkg.go.dev/vuln/GO-2023-1987",
        "https://github.com/CVEProject/cvelistV5/tree/main/cves/2023/29xxx/CVE-2023-29409.json",
        "https://nvd.nist.gov/vuln/detail/CVE-2023-29409",
        "https://security.gentoo.org/glsa/202311-09",
        "https://security.netapp.com/advisory/ntap-20230831-0010/"
      ],
      "provider_metadata": {
        "cna_assigner": "Go",
        "unresolved_ranges": [
          {
            "extracted_events": [
              {
                "range": [
                  {
                    "fixed": "1.19.12"
                  },
                  {
                    "introduced": "1.20.0-0"
                  },
                  {
                    "fixed": "1.20.7"
                  },
                  {
                    "introduced": "1.21.0-0"
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                  {
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                  }
                ],
                "source": "AFFECTED_FIELD",
                "strategy": "StandardRange"
              }
            ]
          }
        ],
        "osv_generated_from": "https://github.com/CVEProject/cvelistV5/tree/main/cves/2023/29xxx/CVE-2023-29409.json"
      }
    },
    "related_cves": [
      {
        "value": "CVE-2023-29409",
        "evidence": "/id"
      }
    ],
    "security_relevant": true,
    "severity_evidence": null
  },
  "source_id": "core-osv",
  "document_id": 498726,
  "published_at": "2023-08-02T19:47:23.829+00:00"
}