CVE-2026-4786 (GCVE-0-2026-4786)

Vulnerability from cvelistv5 – Published: 2026-04-13 21:52 – Updated: 2026-06-10 19:01
VLAI
Title
Incomplete mitigation of CVE-2026-4519, %action expansion for command injection to webbrowser.open()
Summary
Mitgation of CVE-2026-4519 was incomplete. If the URL contained "%action" the mitigation could be bypassed for certain browser types the "webbrowser.open()" API could have commands injected into the underlying shell. See CVE-2026-4519 for details.
Severity
7 (High)
CVSS:4.0/AV:L/AC:L/AT:P/PR:N/UI:A/VC:H/VI:H/VA:N/SC:N/SI:N/SA:N
SSVC
Exploitation: none Automatable: no Technical Impact: total
CISA Coordinator (v2.0.3)
CWE
Assigner
PSF
References
Impacted products
Vendor Product Version
Python Software Foundation CPython Affected: 0 , < 3.13.14 (python)
Affected: 3.14.0a1 , < 3.14.5rc1 (python)
Affected: 3.15.0a1 , < 3.15.0b1 (python)
Create a notification for this product.
Credits
an7y Seth Larson Stan Ulbrych
Show details on NVD website
To clipboard 

{
  "containers": {
    "adp": [
      {
        "metrics": [
          {
            "other": {
              "content": {
                "id": "CVE-2026-4786",
                "options": [
                  {
                    "Exploitation": "none"
                  },
                  {
                    "Automatable": "no"
                  },
                  {
                    "Technical Impact": "total"
                  }
                ],
                "role": "CISA Coordinator",
                "timestamp": "2026-04-14T13:43:47.712946Z",
                "version": "2.0.3"
              },
              "type": "ssvc"
            }
          }
        ],
        "providerMetadata": {
          "dateUpdated": "2026-04-14T13:43:54.704Z",
          "orgId": "134c704f-9b21-4f2e-91b3-4a467353bcc0",
          "shortName": "CISA-ADP"
        },
        "title": "CISA ADP Vulnrichment"
      }
    ],
    "cna": {
      "affected": [
        {
          "defaultStatus": "unaffected",
          "product": "CPython",
          "repo": "https://github.com/python/cpython",
          "vendor": "Python Software Foundation",
          "versions": [
            {
              "lessThan": "3.13.14",
              "status": "affected",
              "version": "0",
              "versionType": "python"
            },
            {
              "lessThan": "3.14.5rc1",
              "status": "affected",
              "version": "3.14.0a1",
              "versionType": "python"
            },
            {
              "lessThan": "3.15.0b1",
              "status": "affected",
              "version": "3.15.0a1",
              "versionType": "python"
            }
          ]
        }
      ],
      "credits": [
        {
          "lang": "en",
          "type": "reporter",
          "value": "an7y"
        },
        {
          "lang": "en",
          "type": "coordinator",
          "value": "Seth Larson"
        },
        {
          "lang": "en",
          "type": "remediation developer",
          "value": "Stan Ulbrych"
        }
      ],
      "descriptions": [
        {
          "lang": "en",
          "supportingMedia": [
            {
              "type": "text/html",
              "value": "Mitgation of\u0026nbsp;CVE-2026-4519 was incomplete. If the URL contained \"%action\" the mitigation could be bypassed for certain browser types the \"webbrowser.open()\" API could have commands injected into the underlying shell. See\u0026nbsp;CVE-2026-4519 for details."
            }
          ],
          "value": "Mitgation of\u00a0CVE-2026-4519 was incomplete. If the URL contained \"%action\" the mitigation could be bypassed for certain browser types the \"webbrowser.open()\" API could have commands injected into the underlying shell. See\u00a0CVE-2026-4519 for details."
        }
      ],
      "metrics": [
        {
          "cvssV4_0": {
            "Automatable": "NOT_DEFINED",
            "Recovery": "NOT_DEFINED",
            "Safety": "NOT_DEFINED",
            "attackComplexity": "LOW",
            "attackRequirements": "PRESENT",
            "attackVector": "LOCAL",
            "baseScore": 7,
            "baseSeverity": "HIGH",
            "exploitMaturity": "NOT_DEFINED",
            "privilegesRequired": "NONE",
            "providerUrgency": "NOT_DEFINED",
            "subAvailabilityImpact": "NONE",
            "subConfidentialityImpact": "NONE",
            "subIntegrityImpact": "NONE",
            "userInteraction": "ACTIVE",
            "valueDensity": "NOT_DEFINED",
            "vectorString": "CVSS:4.0/AV:L/AC:L/AT:P/PR:N/UI:A/VC:H/VI:H/VA:N/SC:N/SI:N/SA:N",
            "version": "4.0",
            "vulnAvailabilityImpact": "NONE",
            "vulnConfidentialityImpact": "HIGH",
            "vulnIntegrityImpact": "HIGH",
            "vulnerabilityResponseEffort": "NOT_DEFINED"
          },
          "format": "CVSS",
          "scenarios": [
            {
              "lang": "en",
              "value": "GENERAL"
            }
          ]
        }
      ],
      "problemTypes": [
        {
          "descriptions": [
            {
              "cweId": "CWE-77",
              "description": "CWE-77",
              "lang": "en",
              "type": "CWE"
            }
          ]
        }
      ],
      "providerMetadata": {
        "dateUpdated": "2026-06-10T19:01:31.611Z",
        "orgId": "28c92f92-d60d-412d-b760-e73465c3df22",
        "shortName": "PSF"
      },
      "references": [
        {
          "tags": [
            "patch"
          ],
          "url": "https://github.com/python/cpython/pull/148170"
        },
        {
          "tags": [
            "issue-tracking"
          ],
          "url": "https://github.com/python/cpython/issues/148169"
        },
        {
          "tags": [
            "vendor-advisory"
          ],
          "url": "https://mail.python.org/archives/list/security-announce@python.org/thread/JQDUNJVB4AQNTJECSUKOBDU3XCJIPSE5/"
        },
        {
          "tags": [
            "patch"
          ],
          "url": "https://github.com/python/cpython/commit/c5767a72838a8dda9d6dc5d3558075b055c56bca"
        },
        {
          "tags": [
            "patch"
          ],
          "url": "https://github.com/python/cpython/commit/d22922c8a7958353689dc4763dd72da2dea03fff"
        },
        {
          "tags": [
            "patch"
          ],
          "url": "https://github.com/python/cpython/commit/f4654824ae0850ac87227fb270f9057477946769"
        },
        {
          "tags": [
            "patch"
          ],
          "url": "https://github.com/python/cpython/commit/28b4ad38067bbdad34edfcd03ad2de5f06387e53"
        },
        {
          "tags": [
            "patch"
          ],
          "url": "https://github.com/python/cpython/commit/d6d68494be70bdbda20f89f83801ba52ec37daa4"
        }
      ],
      "source": {
        "discovery": "UNKNOWN"
      },
      "title": "Incomplete mitigation of CVE-2026-4519, %action expansion for command injection to webbrowser.open()",
      "x_generator": {
        "engine": "cvelib 1.8.0"
      }
    }
  },
  "cveMetadata": {
    "assignerOrgId": "28c92f92-d60d-412d-b760-e73465c3df22",
    "assignerShortName": "PSF",
    "cveId": "CVE-2026-4786",
    "datePublished": "2026-04-13T21:52:19.036Z",
    "dateReserved": "2026-03-24T19:25:48.269Z",
    "dateUpdated": "2026-06-10T19:01:31.611Z",
    "state": "PUBLISHED"
  },
  "dataType": "CVE_RECORD",
  "dataVersion": "5.2",
  "vulnerability-lookup:meta": {
    "epss": {
      "cve": "CVE-2026-4786",
      "date": "2026-06-29",
      "epss": "0.00209",
      "percentile": "0.11042"
    },
    "nvd": "{\"cve\":{\"id\":\"CVE-2026-4786\",\"sourceIdentifier\":\"cna@python.org\",\"published\":\"2026-04-13T22:16:30.413\",\"lastModified\":\"2026-06-17T10:57:13.147\",\"vulnStatus\":\"Awaiting Analysis\",\"cveTags\":[],\"descriptions\":[{\"lang\":\"en\",\"value\":\"Mitgation of\u00a0CVE-2026-4519 was incomplete. If the URL contained \\\"%action\\\" the mitigation could be bypassed for certain browser types the \\\"webbrowser.open()\\\" API could have commands injected into the underlying shell. See\u00a0CVE-2026-4519 for details.\"}],\"affected\":[{\"source\":\"cna@python.org\",\"affectedData\":[{\"vendor\":\"Python Software Foundation\",\"product\":\"CPython\",\"defaultStatus\":\"unaffected\",\"repo\":\"https://github.com/python/cpython\",\"versions\":[{\"version\":\"0\",\"lessThan\":\"3.13.14\",\"versionType\":\"python\",\"status\":\"affected\"},{\"version\":\"3.14.0a1\",\"lessThan\":\"3.14.5rc1\",\"versionType\":\"python\",\"status\":\"affected\"},{\"version\":\"3.15.0a1\",\"lessThan\":\"3.15.0b1\",\"versionType\":\"python\",\"status\":\"affected\"}]}]}],\"metrics\":{\"cvssMetricV40\":[{\"source\":\"cna@python.org\",\"type\":\"Secondary\",\"cvssData\":{\"version\":\"4.0\",\"vectorString\":\"CVSS:4.0/AV:L/AC:L/AT:P/PR:N/UI:A/VC:H/VI:H/VA:N/SC:N/SI:N/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X\",\"baseScore\":7.0,\"baseSeverity\":\"HIGH\",\"attackVector\":\"LOCAL\",\"attackComplexity\":\"LOW\",\"attackRequirements\":\"PRESENT\",\"privilegesRequired\":\"NONE\",\"userInteraction\":\"ACTIVE\",\"vulnConfidentialityImpact\":\"HIGH\",\"vulnIntegrityImpact\":\"HIGH\",\"vulnAvailabilityImpact\":\"NONE\",\"subConfidentialityImpact\":\"NONE\",\"subIntegrityImpact\":\"NONE\",\"subAvailabilityImpact\":\"NONE\",\"exploitMaturity\":\"NOT_DEFINED\",\"confidentialityRequirement\":\"NOT_DEFINED\",\"integrityRequirement\":\"NOT_DEFINED\",\"availabilityRequirement\":\"NOT_DEFINED\",\"modifiedAttackVector\":\"NOT_DEFINED\",\"modifiedAttackComplexity\":\"NOT_DEFINED\",\"modifiedAttackRequirements\":\"NOT_DEFINED\",\"modifiedPrivilegesRequired\":\"NOT_DEFINED\",\"modifiedUserInteraction\":\"NOT_DEFINED\",\"modifiedVulnConfidentialityImpact\":\"NOT_DEFINED\",\"modifiedVulnIntegrityImpact\":\"NOT_DEFINED\",\"modifiedVulnAvailabilityImpact\":\"NOT_DEFINED\",\"modifiedSubConfidentialityImpact\":\"NOT_DEFINED\",\"modifiedSubIntegrityImpact\":\"NOT_DEFINED\",\"modifiedSubAvailabilityImpact\":\"NOT_DEFINED\",\"Safety\":\"NOT_DEFINED\",\"Automatable\":\"NOT_DEFINED\",\"Recovery\":\"NOT_DEFINED\",\"valueDensity\":\"NOT_DEFINED\",\"vulnerabilityResponseEffort\":\"NOT_DEFINED\",\"providerUrgency\":\"NOT_DEFINED\"}}],\"ssvcV203\":[{\"source\":\"134c704f-9b21-4f2e-91b3-4a467353bcc0\",\"ssvcData\":{\"timestamp\":\"2026-04-14T13:43:47.712946Z\",\"id\":\"CVE-2026-4786\",\"options\":[{\"exploitation\":\"none\"},{\"automatable\":\"no\"},{\"technicalImpact\":\"total\"}],\"role\":\"CISA Coordinator\",\"version\":\"2.0.3\"}}]},\"weaknesses\":[{\"source\":\"cna@python.org\",\"type\":\"Secondary\",\"description\":[{\"lang\":\"en\",\"value\":\"CWE-77\"}]}],\"references\":[{\"url\":\"https://github.com/python/cpython/commit/28b4ad38067bbdad34edfcd03ad2de5f06387e53\",\"source\":\"cna@python.org\"},{\"url\":\"https://github.com/python/cpython/commit/c5767a72838a8dda9d6dc5d3558075b055c56bca\",\"source\":\"cna@python.org\"},{\"url\":\"https://github.com/python/cpython/commit/d22922c8a7958353689dc4763dd72da2dea03fff\",\"source\":\"cna@python.org\"},{\"url\":\"https://github.com/python/cpython/commit/d6d68494be70bdbda20f89f83801ba52ec37daa4\",\"source\":\"cna@python.org\"},{\"url\":\"https://github.com/python/cpython/commit/f4654824ae0850ac87227fb270f9057477946769\",\"source\":\"cna@python.org\"},{\"url\":\"https://github.com/python/cpython/issues/148169\",\"source\":\"cna@python.org\"},{\"url\":\"https://github.com/python/cpython/pull/148170\",\"source\":\"cna@python.org\"},{\"url\":\"https://mail.python.org/archives/list/security-announce@python.org/thread/JQDUNJVB4AQNTJECSUKOBDU3XCJIPSE5/\",\"source\":\"cna@python.org\"}]}}",
    "vulnrichment": {
      "containers": "{\"adp\": [{\"title\": \"CISA ADP Vulnrichment\", \"metrics\": [{\"other\": {\"type\": \"ssvc\", \"content\": {\"id\": \"CVE-2026-4786\", \"role\": \"CISA Coordinator\", \"options\": [{\"Exploitation\": \"none\"}, {\"Automatable\": \"no\"}, {\"Technical Impact\": \"total\"}], \"version\": \"2.0.3\", \"timestamp\": \"2026-04-14T13:43:47.712946Z\"}}}], \"providerMetadata\": {\"orgId\": \"134c704f-9b21-4f2e-91b3-4a467353bcc0\", \"shortName\": \"CISA-ADP\", \"dateUpdated\": \"2026-04-14T13:43:51.497Z\"}}], \"cna\": {\"title\": \"Incomplete mitigation of CVE-2026-4519, %action expansion for command injection to webbrowser.open()\", \"source\": {\"discovery\": \"UNKNOWN\"}, \"credits\": [{\"lang\": \"en\", \"type\": \"reporter\", \"value\": \"an7y\"}, {\"lang\": \"en\", \"type\": \"coordinator\", \"value\": \"Seth Larson\"}, {\"lang\": \"en\", \"type\": \"remediation developer\", \"value\": \"Stan Ulbrych\"}], \"metrics\": [{\"format\": \"CVSS\", \"cvssV4_0\": {\"Safety\": \"NOT_DEFINED\", \"version\": \"4.0\", \"Recovery\": \"NOT_DEFINED\", \"baseScore\": 7, \"Automatable\": \"NOT_DEFINED\", \"attackVector\": \"LOCAL\", \"baseSeverity\": \"HIGH\", \"valueDensity\": \"NOT_DEFINED\", \"vectorString\": \"CVSS:4.0/AV:L/AC:L/AT:P/PR:N/UI:A/VC:H/VI:H/VA:N/SC:N/SI:N/SA:N\", \"exploitMaturity\": \"NOT_DEFINED\", \"providerUrgency\": \"NOT_DEFINED\", \"userInteraction\": \"ACTIVE\", \"attackComplexity\": \"LOW\", \"attackRequirements\": \"PRESENT\", \"privilegesRequired\": \"NONE\", \"subIntegrityImpact\": \"NONE\", \"vulnIntegrityImpact\": \"HIGH\", \"subAvailabilityImpact\": \"NONE\", \"vulnAvailabilityImpact\": \"NONE\", \"subConfidentialityImpact\": \"NONE\", \"vulnConfidentialityImpact\": \"HIGH\", \"vulnerabilityResponseEffort\": \"NOT_DEFINED\"}, \"scenarios\": [{\"lang\": \"en\", \"value\": \"GENERAL\"}]}], \"affected\": [{\"repo\": \"https://github.com/python/cpython\", \"vendor\": \"Python Software Foundation\", \"product\": \"CPython\", \"versions\": [{\"status\": \"affected\", \"version\": \"0\", \"lessThan\": \"3.15.0\", \"versionType\": \"python\"}], \"defaultStatus\": \"unaffected\"}], \"references\": [{\"url\": \"https://github.com/python/cpython/pull/148170\", \"tags\": [\"patch\"]}, {\"url\": \"https://github.com/python/cpython/issues/148169\", \"tags\": [\"issue-tracking\"]}, {\"url\": \"https://mail.python.org/archives/list/security-announce@python.org/thread/JQDUNJVB4AQNTJECSUKOBDU3XCJIPSE5/\", \"tags\": [\"vendor-advisory\"]}, {\"url\": \"https://github.com/python/cpython/commit/c5767a72838a8dda9d6dc5d3558075b055c56bca\", \"tags\": [\"patch\"]}, {\"url\": \"https://github.com/python/cpython/commit/d22922c8a7958353689dc4763dd72da2dea03fff\", \"tags\": [\"patch\"]}, {\"url\": \"https://github.com/python/cpython/commit/f4654824ae0850ac87227fb270f9057477946769\", \"tags\": [\"patch\"]}, {\"url\": \"https://github.com/python/cpython/commit/28b4ad38067bbdad34edfcd03ad2de5f06387e53\", \"tags\": [\"patch\"]}, {\"url\": \"https://github.com/python/cpython/commit/d6d68494be70bdbda20f89f83801ba52ec37daa4\", \"tags\": [\"patch\"]}], \"x_generator\": {\"engine\": \"cvelib 1.8.0\"}, \"descriptions\": [{\"lang\": \"en\", \"value\": \"Mitgation of\\u00a0CVE-2026-4519 was incomplete. If the URL contained \\\"%action\\\" the mitigation could be bypassed for certain browser types the \\\"webbrowser.open()\\\" API could have commands injected into the underlying shell. See\\u00a0CVE-2026-4519 for details.\", \"supportingMedia\": [{\"type\": \"text/html\", \"value\": \"Mitgation of\u0026nbsp;CVE-2026-4519 was incomplete. If the URL contained \\\"%action\\\" the mitigation could be bypassed for certain browser types the \\\"webbrowser.open()\\\" API could have commands injected into the underlying shell. See\u0026nbsp;CVE-2026-4519 for details.\"}]}], \"problemTypes\": [{\"descriptions\": [{\"lang\": \"en\", \"type\": \"CWE\", \"cweId\": \"CWE-77\", \"description\": \"CWE-77\"}]}], \"providerMetadata\": {\"orgId\": \"28c92f92-d60d-412d-b760-e73465c3df22\", \"shortName\": \"PSF\", \"dateUpdated\": \"2026-04-29T15:30:58.707Z\"}}}",
      "cveMetadata": "{\"cveId\": \"CVE-2026-4786\", \"state\": \"PUBLISHED\", \"dateUpdated\": \"2026-04-29T15:30:58.707Z\", \"dateReserved\": \"2026-03-24T19:25:48.269Z\", \"assignerOrgId\": \"28c92f92-d60d-412d-b760-e73465c3df22\", \"datePublished\": \"2026-04-13T21:52:19.036Z\", \"assignerShortName\": \"PSF\"}",
      "dataType": "CVE_RECORD",
      "dataVersion": "5.2"
    }
  }
}


Log in or create an account to share your comment.




Tags
Taxonomy of the tags.





Forecast uses a logistic model when the trend is rising, or an exponential decay model when the trend is falling. Fitted via linearized least squares.

Sightings

Author Source Type Date Other

Nomenclature

  • Seen: The vulnerability was mentioned, discussed, or observed by the user.
  • Confirmed: The vulnerability has been validated from an analyst's perspective.
  • Published Proof of Concept: A public proof of concept is available for this vulnerability.
  • Exploited: The vulnerability was observed as exploited by the user who reported the sighting.
  • Patched: The vulnerability was observed as successfully patched by the user who reported the sighting.
  • Not exploited: The vulnerability was not observed as exploited by the user who reported the sighting.
  • Not confirmed: The user expressed doubt about the validity of the vulnerability.
  • Not patched: The vulnerability was not observed as successfully patched by the user who reported the sighting.


Detection rules are retrieved from Rulezet.