Capgo - Subkey Enforcement Bypass via x-limited-key-id Header Parsing

Capgo before 12.128.2 contains a weak parsing vulnerability in the x-limited-key-id header that allows attackers to bypass subkey enforcement by submitting malformed values, zero, or duplicate headers that result in NaN or falsy values. Remote attackers can manipulate the x-limited-key-id header to disable limited key scoping and execute requests using the main API key context instead of restricted subkey permissions.

Problem type

Improper Input Validation

Affected products

Capgo

Capgo

< 12.128.2 - AFFECTED

12.128.2 - UNAFFECTED

References

GitHub Security Advisory (GHSA-42vv-8j94-24wj)

https://github.com/Cap-go/capgo/security/advisories/GHSA-42vv-8j94-24wj

vendor-advisory

VulnCheck Advisory: Capgo - Subkey Enforcement Bypass via x-limited-key-id Header Parsing

https://www.vulncheck.com/advisories/capgo-subkey-enforcement-bypass-via-x-limited-key-id-header-parsing

third-party-advisory

JSON source

https://cveawg.mitre.org/api/cve/CVE-2026-56306

Click to expand

{
  "dataType": "CVE_RECORD",
  "dataVersion": "5.2",
  "cveMetadata": {
    "cveId": "CVE-2026-56306",
    "assignerOrgId": "83251b91-4cc7-4094-a5c7-464a1b83ea10",
    "assignerShortName": "VulnCheck",
    "dateUpdated": "2026-06-22T21:04:46.832Z",
    "dateReserved": "2026-06-20T12:53:19.893Z",
    "datePublished": "2026-06-22T21:04:46.832Z",
    "state": "PUBLISHED"
  },
  "containers": {
    "cna": {
      "providerMetadata": {
        "orgId": "83251b91-4cc7-4094-a5c7-464a1b83ea10",
        "shortName": "VulnCheck",
        "dateUpdated": "2026-06-22T21:04:46.832Z"
      },
      "datePublic": "2026-05-07T00:00:00.000Z",
      "title": "Capgo - Subkey Enforcement Bypass via x-limited-key-id Header Parsing",
      "descriptions": [
        {
          "lang": "en",
          "value": "Capgo before 12.128.2 contains a weak parsing vulnerability in the x-limited-key-id header that allows attackers to bypass subkey enforcement by submitting malformed values, zero, or duplicate headers that result in NaN or falsy values. Remote attackers can manipulate the x-limited-key-id header to disable limited key scoping and execute requests using the main API key context instead of restricted subkey permissions."
        }
      ],
      "affected": [
        {
          "vendor": "Capgo",
          "product": "Capgo",
          "defaultStatus": "unaffected",
          "versions": [
            {
              "version": "0",
              "status": "affected",
              "versionType": "semver",
              "lessThan": "12.128.2"
            },
            {
              "version": "12.128.2",
              "status": "unaffected",
              "versionType": "semver"
            }
          ]
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      ],
      "problemTypes": [
        {
          "descriptions": [
            {
              "lang": "en",
              "description": "Improper Input Validation",
              "cweId": "CWE-20",
              "type": "CWE"
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          "url": "https://github.com/Cap-go/capgo/security/advisories/GHSA-42vv-8j94-24wj",
          "name": "GitHub Security Advisory (GHSA-42vv-8j94-24wj)",
          "tags": [
            "vendor-advisory"
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        },
        {
          "url": "https://www.vulncheck.com/advisories/capgo-subkey-enforcement-bypass-via-x-limited-key-id-header-parsing",
          "name": "VulnCheck Advisory: Capgo - Subkey Enforcement Bypass via x-limited-key-id Header Parsing",
          "tags": [
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      "metrics": [
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            "vectorString": "CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:C/C:L/I:L/A:N",
            "attackVector": "NETWORK",
            "attackComplexity": "LOW",
            "privilegesRequired": "LOW",
            "userInteraction": "NONE",
            "scope": "CHANGED",
            "confidentialityImpact": "LOW",
            "integrityImpact": "LOW",
            "availabilityImpact": "NONE",
            "baseScore": 6.4,
            "baseSeverity": "MEDIUM"
          }
        }
      ],
      "credits": [
        {
          "lang": "en",
          "value": "Judel777",
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}