Vulnerability-Lookup

CVE-2026-53424 (GCVE-0-2026-53424)

Vulnerability from cvelistv5 – Published: 2026-08-20 17:27 – Updated: 2026-08-20 18:37

Title

Missing one-time-use enforcement in Samly allows replay of SAML bearer assertions

Summary

Authentication Bypass by Capture-replay vulnerability in dropbox samly allows an attacker to authenticate as the subject of a captured SAML assertion by resubmitting it. Samly.Helper.decode_idp_auth_resp/3 in lib/samly/helper.ex calls esaml_sp:validate_assertion/2, whose default duplicate detector is a no-op. The /3 arity accepting a DuplicateFun exists in esaml and implements the check, but Samly never calls it and offers no configuration to supply one, so the SAML 2.0 Web Browser SSO Profile requirement that a bearer assertion be used once is unenforced. An attacker holding a valid SAMLResponse obtained from the network, from browser history, or from logs can submit the identical bytes repeatedly until the assertion's NotOnOrAfter passes, each time establishing a session as the assertion's subject. This issue affects samly: from 0.3.0 onward.

Severity

9.1 (Critical)


                        
                          CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:H/VI:H/VA:N/SC:N/SI:N/SA:N

CWE

CWE-294 - Authentication Bypass by Capture-replay

Assigner

EEF mitre root

References

2 references

URL	Tags
https://cna.erlef.org/cves/CVE-2026-53424.html	relatedthird-party-advisory
https://osv.dev/vulnerability/EEF-CVE-2026-53424	related

Impacted products

3 products

Vendor	Product	Version
dropbox	samly	Affected: 0.3.0 , < * (semver) cpe:2.3:a:dropbox:samly::::::::
dropbox	samly	Affected: 8a5bb1b4a4753d05470da2036323477f63cfdf4c , < * (git) cpe:2.3:a:dropbox:samly::::::::
handnot2	samly	Affected: 8a5bb1b4a4753d05470da2036323477f63cfdf4c , < * (git) cpe:2.3:a:handnot2:samly::::::::

Credits

Mark Madsen Jonatan Männchen / EEF

Show details on NVD website

JSON

To clipboard

{
  "containers": {
    "cna": {
      "affected": [
        {
          "collectionURL": "https://repo.hex.pm",
          "cpes": [
            "cpe:2.3:a:dropbox:samly:*:*:*:*:*:*:*:*"
          ],
          "defaultStatus": "unaffected",
          "modules": [
            "\u0027Elixir.Samly.Helper\u0027"
          ],
          "packageName": "samly",
          "packageURL": "pkg:hex/samly",
          "product": "samly",
          "programFiles": [
            "lib/samly/helper.ex"
          ],
          "programRoutines": [
            {
              "name": "\u0027Elixir.Samly.Helper\u0027:decode_idp_auth_resp/3"
            }
          ],
          "repo": "https://github.com/dropbox/samly",
          "vendor": "dropbox",
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            }
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                },
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      "credits": [
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          "type": "reporter",
          "value": "Mark Madsen"
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        {
          "lang": "en",
          "type": "coordinator",
          "value": "Jonatan M\u00e4nnchen / EEF"
        }
      ],
      "descriptions": [
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          "lang": "en",
          "supportingMedia": [
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              "type": "text/html",
              "value": "\u003cp\u003eAuthentication Bypass by Capture-replay vulnerability in dropbox samly allows an attacker to authenticate as the subject of a captured SAML assertion by resubmitting it.\u003c/p\u003e\n\u003cp\u003e\u003ccode\u003eSamly.Helper.decode_idp_auth_resp/3\u003c/code\u003e in \u003ccode\u003elib/samly/helper.ex\u003c/code\u003e calls \u003ccode\u003eesaml_sp:validate_assertion/2\u003c/code\u003e, whose default duplicate detector is a no-op. The \u003ccode\u003e/3\u003c/code\u003e arity accepting a \u003ccode\u003eDuplicateFun\u003c/code\u003e exists in \u003ccode\u003eesaml\u003c/code\u003e and implements the check, but Samly never calls it and offers no configuration to supply one, so the SAML 2.0 Web Browser SSO Profile requirement that a bearer assertion be used once is unenforced. An attacker holding a valid \u003ccode\u003eSAMLResponse\u003c/code\u003e obtained from the network, from browser history, or from logs can submit the identical bytes repeatedly until the assertion\u0027s \u003ccode\u003eNotOnOrAfter\u003c/code\u003e passes, each time establishing a session as the assertion\u0027s subject.\u003c/p\u003e\n\u003cp\u003eThis issue affects samly: from 0.3.0 onward.\u003c/p\u003e"
            },
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              "value": "Authentication Bypass by Capture-replay vulnerability in dropbox samly allows an attacker to authenticate as the subject of a captured SAML assertion by resubmitting it.\n\n`Samly.Helper.decode_idp_auth_resp/3` in `lib/samly/helper.ex` calls `esaml_sp:validate_assertion/2`, whose default duplicate detector is a no-op. The `/3` arity accepting a `DuplicateFun` exists in `esaml` and implements the check, but Samly never calls it and offers no configuration to supply one, so the SAML 2.0 Web Browser SSO Profile requirement that a bearer assertion be used once is unenforced. An attacker holding a valid `SAMLResponse` obtained from the network, from browser history, or from logs can submit the identical bytes repeatedly until the assertion\u0027s `NotOnOrAfter` passes, each time establishing a session as the assertion\u0027s subject.\n\nThis issue affects samly: from 0.3.0 onward."
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        }
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            "version": "4.0",
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          ]
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      ],
      "providerMetadata": {
        "dateUpdated": "2026-08-20T18:37:24.439Z",
        "orgId": "6b3ad84c-e1a6-4bf7-a703-f496b71e49db",
        "shortName": "EEF"
      },
      "references": [
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            "third-party-advisory"
          ],
          "url": "https://cna.erlef.org/cves/CVE-2026-53424.html"
        },
        {
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          "url": "https://osv.dev/vulnerability/EEF-CVE-2026-53424"
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      ],
      "source": {
        "discovery": "UNKNOWN"
      },
      "title": "Missing one-time-use enforcement in Samly allows replay of SAML bearer assertions"
    }
  },
  "cveMetadata": {
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    "datePublished": "2026-08-20T17:27:11.115Z",
    "dateReserved": "2026-06-09T11:01:47.529Z",
    "dateUpdated": "2026-08-20T18:37:24.439Z",
    "state": "PUBLISHED"
  },
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An attacker holding a valid SAMLResponse obtained from the network, from browser history, or from logs can submit the identical bytes repeatedly until the assertion\u0027s NotOnOrAfter passes, each time establishing a session as the assertion\u0027s subject.\\n\\nThis issue affects samly: from 0.3.0 onward.\"}],\"affected\":[{\"source\":\"6b3ad84c-e1a6-4bf7-a703-f496b71e49db\",\"affectedData\":[{\"vendor\":\"dropbox\",\"product\":\"samly\",\"defaultStatus\":\"unaffected\",\"collectionURL\":\"https://repo.hex.pm\",\"packageName\":\"samly\",\"cpes\":[\"cpe:2.3:a:dropbox:samly:*:*:*:*:*:*:*:*\"],\"modules\":[\"\u0027Elixir.Samly.Helper\u0027\"],\"programFiles\":[\"lib/samly/helper.ex\"],\"programRoutines\":[{\"name\":\"\u0027Elixir.Samly.Helper\u0027:decode_idp_auth_resp/3\"}],\"repo\":\"https://github.com/dropbox/samly\",\"packageURL\":\"pkg:hex/samly\",\"versions\":[{\"version\":\"0.3.0\",\"lessThan\":\"*\",\"versionType\":\"semver\",\"status\":\"affected\"}]},{\"vendor\":\"dropbox\",\"product\":\"samly\",\"defaultStatus\":\"unaffected\",\"collectionURL\":\"https://github.com\",\"packageName\":\"dropbox/samly\",\"cpes\":[\"cpe:2.3:a:dropbox:samly:*:*:*:*:*:*:*:*\"],\"modules\":[\"\u0027Elixir.Samly.Helper\u0027\"],\"programFiles\":[\"lib/samly/helper.ex\"],\"programRoutines\":[{\"name\":\"\u0027Elixir.Samly.Helper\u0027:decode_idp_auth_resp/3\"}],\"repo\":\"https://github.com/dropbox/samly\",\"packageURL\":\"pkg:github/dropbox/samly\",\"versions\":[{\"version\":\"8a5bb1b4a4753d05470da2036323477f63cfdf4c\",\"lessThan\":\"*\",\"versionType\":\"git\",\"status\":\"affected\"}]},{\"vendor\":\"handnot2\",\"product\":\"samly\",\"defaultStatus\":\"unaffected\",\"collectionURL\":\"https://github.com\",\"packageName\":\"handnot2/samly\",\"cpes\":[\"cpe:2.3:a:handnot2:samly:*:*:*:*:*:*:*:*\"],\"modules\":[\"\u0027Elixir.Samly.Helper\u0027\"],\"programFiles\":[\"lib/samly/helper.ex\"],\"programRoutines\":[{\"name\":\"\u0027Elixir.Samly.Helper\u0027:decode_idp_auth_resp/3\"}],\"repo\":\"https://github.com/handnot2/samly\",\"packageURL\":\"pkg:github/handnot2/samly\",\"versions\":[{\"version\":\"8a5bb1b4a4753d05470da2036323477f63cfdf4c\",\"lessThan\":\"*\",\"versionType\":\"git\",\"status\":\"affected\"}]}]}],\"metrics\":{\"cvssMetricV40\":[{\"source\":\"6b3ad84c-e1a6-4bf7-a703-f496b71e49db\",\"type\":\"Secondary\",\"cvssData\":{\"version\":\"4.0\",\"vectorString\":\"CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/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\":9.1,\"baseSeverity\":\"CRITICAL\",\"attackVector\":\"NETWORK\",\"attackComplexity\":\"LOW\",\"attackRequirements\":\"PRESENT\",\"privilegesRequired\":\"NONE\",\"userInteraction\":\"NONE\",\"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\"}}]},\"weaknesses\":[{\"source\":\"6b3ad84c-e1a6-4bf7-a703-f496b71e49db\",\"type\":\"Secondary\",\"description\":[{\"lang\":\"en\",\"value\":\"CWE-294\"}]}],\"references\":[{\"url\":\"https://cna.erlef.org/cves/CVE-2026-53424.html\",\"source\":\"6b3ad84c-e1a6-4bf7-a703-f496b71e49db\"},{\"url\":\"https://osv.dev/vulnerability/EEF-CVE-2026-53424\",\"source\":\"6b3ad84c-e1a6-4bf7-a703-f496b71e49db\"}]}}"
  }
}

FKIE_CVE-2026-53424

Vulnerability from fkie_nvd - Published: 2026-08-20 18:16 - Updated: 2026-08-20 19:16

Severity

9.1 (Critical) - CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:H/VI:H/VA:N/SC:N/SI:N/SA:N

Summary

References

	URL	Tags
	6b3ad84c-e1a6-4bf7-a703-f496b71e49db	https://cna.erlef.org/cves/CVE-2026-53424.html
	6b3ad84c-e1a6-4bf7-a703-f496b71e49db	https://osv.dev/vulnerability/EEF-CVE-2026-53424

Impacted products

	Vendor	Product	Version

JSON

To clipboard

{
  "affected": [
    {
      "affectedData": [
        {
          "collectionURL": "https://repo.hex.pm",
          "cpes": [
            "cpe:2.3:a:dropbox:samly:*:*:*:*:*:*:*:*"
          ],
          "defaultStatus": "unaffected",
          "modules": [
            "\u0027Elixir.Samly.Helper\u0027"
          ],
          "packageName": "samly",
          "packageURL": "pkg:hex/samly",
          "product": "samly",
          "programFiles": [
            "lib/samly/helper.ex"
          ],
          "programRoutines": [
            {
              "name": "\u0027Elixir.Samly.Helper\u0027:decode_idp_auth_resp/3"
            }
          ],
          "repo": "https://github.com/dropbox/samly",
          "vendor": "dropbox",
          "versions": [
            {
              "lessThan": "*",
              "status": "affected",
              "version": "0.3.0",
              "versionType": "semver"
            }
          ]
        },
        {
          "collectionURL": "https://github.com",
          "cpes": [
            "cpe:2.3:a:dropbox:samly:*:*:*:*:*:*:*:*"
          ],
          "defaultStatus": "unaffected",
          "modules": [
            "\u0027Elixir.Samly.Helper\u0027"
          ],
          "packageName": "dropbox/samly",
          "packageURL": "pkg:github/dropbox/samly",
          "product": "samly",
          "programFiles": [
            "lib/samly/helper.ex"
          ],
          "programRoutines": [
            {
              "name": "\u0027Elixir.Samly.Helper\u0027:decode_idp_auth_resp/3"
            }
          ],
          "repo": "https://github.com/dropbox/samly",
          "vendor": "dropbox",
          "versions": [
            {
              "lessThan": "*",
              "status": "affected",
              "version": "8a5bb1b4a4753d05470da2036323477f63cfdf4c",
              "versionType": "git"
            }
          ]
        },
        {
          "collectionURL": "https://github.com",
          "cpes": [
            "cpe:2.3:a:handnot2:samly:*:*:*:*:*:*:*:*"
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            "\u0027Elixir.Samly.Helper\u0027"
          ],
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            "lib/samly/helper.ex"
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            {
              "name": "\u0027Elixir.Samly.Helper\u0027:decode_idp_auth_resp/3"
            }
          ],
          "repo": "https://github.com/handnot2/samly",
          "vendor": "handnot2",
          "versions": [
            {
              "lessThan": "*",
              "status": "affected",
              "version": "8a5bb1b4a4753d05470da2036323477f63cfdf4c",
              "versionType": "git"
            }
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      ],
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    }
  ],
  "cveTags": [],
  "descriptions": [
    {
      "lang": "en",
      "value": "Authentication Bypass by Capture-replay vulnerability in dropbox samly allows an attacker to authenticate as the subject of a captured SAML assertion by resubmitting it.\n\nSamly.Helper.decode_idp_auth_resp/3 in lib/samly/helper.ex calls esaml_sp:validate_assertion/2, whose default duplicate detector is a no-op. The /3 arity accepting a DuplicateFun exists in esaml and implements the check, but Samly never calls it and offers no configuration to supply one, so the SAML 2.0 Web Browser SSO Profile requirement that a bearer assertion be used once is unenforced. An attacker holding a valid SAMLResponse obtained from the network, from browser history, or from logs can submit the identical bytes repeatedly until the assertion\u0027s NotOnOrAfter passes, each time establishing a session as the assertion\u0027s subject.\n\nThis issue affects samly: from 0.3.0 onward."
    }
  ],
  "id": "CVE-2026-53424",
  "lastModified": "2026-08-20T19:16:54.057",
  "metrics": {
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      {
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          "Recovery": "NOT_DEFINED",
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          "version": "4.0",
          "vulnAvailabilityImpact": "NONE",
          "vulnConfidentialityImpact": "HIGH",
          "vulnIntegrityImpact": "HIGH",
          "vulnerabilityResponseEffort": "NOT_DEFINED"
        },
        "source": "6b3ad84c-e1a6-4bf7-a703-f496b71e49db",
        "type": "Secondary"
      }
    ]
  },
  "published": "2026-08-20T18:16:27.680",
  "references": [
    {
      "source": "6b3ad84c-e1a6-4bf7-a703-f496b71e49db",
      "url": "https://cna.erlef.org/cves/CVE-2026-53424.html"
    },
    {
      "source": "6b3ad84c-e1a6-4bf7-a703-f496b71e49db",
      "url": "https://osv.dev/vulnerability/EEF-CVE-2026-53424"
    }
  ],
  "sourceIdentifier": "6b3ad84c-e1a6-4bf7-a703-f496b71e49db",
  "vulnStatus": "Received",
  "weaknesses": [
    {
      "description": [
        {
          "lang": "en",
          "value": "CWE-294"
        }
      ],
      "source": "6b3ad84c-e1a6-4bf7-a703-f496b71e49db",
      "type": "Secondary"
    }
  ]
}

GHSA-5X87-GF34-8WW7

Vulnerability from github – Published: 2026-08-20 18:30 – Updated: 2026-08-20 18:30

Details

Authentication Bypass by Capture-replay vulnerability in dropbox samly allows an attacker to authenticate as the subject of a captured SAML assertion by resubmitting it.

Samly.Helper.decode_idp_auth_resp/3 in lib/samly/helper.ex calls esaml_sp:validate_assertion/2, whose default duplicate detector is a no-op. The /3 arity accepting a DuplicateFun exists in esaml and implements the check, but Samly never calls it and offers no configuration to supply one, so the SAML 2.0 Web Browser SSO Profile requirement that a bearer assertion be used once is unenforced. An attacker holding a valid SAMLResponse obtained from the network, from browser history, or from logs can submit the identical bytes repeatedly until the assertion's NotOnOrAfter passes, each time establishing a session as the assertion's subject.

This issue affects samly: from v0.3.0 onward.

Severity

9.1 (Critical)


                  
                    CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:H/VI:H/VA:N/SC:N/SI:N/SA:N

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{
  "affected": [],
  "aliases": [
    "CVE-2026-53424"
  ],
  "database_specific": {
    "cwe_ids": [
      "CWE-294"
    ],
    "github_reviewed": false,
    "github_reviewed_at": null,
    "nvd_published_at": "2026-08-20T18:16:27Z",
    "severity": "CRITICAL"
  },
  "details": "Authentication Bypass by Capture-replay vulnerability in dropbox samly allows an attacker to authenticate as the subject of a captured SAML assertion by resubmitting it.\n\nSamly.Helper.decode_idp_auth_resp/3 in lib/samly/helper.ex calls esaml_sp:validate_assertion/2, whose default duplicate detector is a no-op. The /3 arity accepting a DuplicateFun exists in esaml and implements the check, but Samly never calls it and offers no configuration to supply one, so the SAML 2.0 Web Browser SSO Profile requirement that a bearer assertion be used once is unenforced. An attacker holding a valid SAMLResponse obtained from the network, from browser history, or from logs can submit the identical bytes repeatedly until the assertion\u0027s NotOnOrAfter passes, each time establishing a session as the assertion\u0027s subject.\n\nThis issue affects samly: from v0.3.0 onward.",
  "id": "GHSA-5x87-gf34-8ww7",
  "modified": "2026-08-20T18:30:59Z",
  "published": "2026-08-20T18:30:59Z",
  "references": [
    {
      "type": "ADVISORY",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-53424"
    },
    {
      "type": "WEB",
      "url": "https://cna.erlef.org/cves/CVE-2026-53424.html"
    },
    {
      "type": "WEB",
      "url": "https://osv.dev/vulnerability/EEF-CVE-2026-53424"
    }
  ],
  "schema_version": "1.4.0",
  "severity": [
    {
      "score": "CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/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",
      "type": "CVSS_V4"
    }
  ]
}

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.

The MITRE ATT&CK techniques below are AI-generated suggestions, inferred from the description of the vulnerability by the CIRCL/vulnerability-attack-technique-classification-roberta-base model, served locally by ML-Gateway. They have not been verified by an analyst and are provided for guidance only.
The approach is described in our paper Mapping CVEs to MITRE ATT&CK Techniques: A Curated Gold-Set Classifier and the Limits of LLM-Assisted Label Expansion.

Action not permitted

CVE-2026-53424 (GCVE-0-2026-53424)

FKIE_CVE-2026-53424

GHSA-5X87-GF34-8WW7

Tags

Sightings

Nomenclature