Vulnerability-Lookup

CVE-2026-73314 (GCVE-0-2026-73314)

Vulnerability from cvelistv5 – Published: 2026-09-08 13:17 – Updated: 2026-09-10 13:46

Title

XenForo < 2.3.13 Signature Verification Bypass via PayPal REST Webhook

Summary

XenForo before 2.3.13 contains a signature verification logic error in the PayPal REST webhook handler that allows unauthenticated attackers to bypass payment signature validation by submitting a webhook request with an unsupported auth_algo header value. When the algorithm cannot be mapped to a supported hash function, the verification function incorrectly returns true instead of failing, causing the caller to treat the fabricated request as verified and process the payment event without a valid PayPal signature.

Severity

8.7 (High)


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

7.5 (High)


                        
                          CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N

SSVC

Exploitation: poc Automatable: yes Technical Impact: partial

CISA Coordinator · CISA-ADP (v2.0.3)

Decision recorded 2026-09-10 13:46 UTC

CWE

CWE-754 - Improper Check for Unusual or Exceptional Conditions

Assigner

VulnCheck mitre root

References

5 references

URL	Tags
https://xenforo.com/community/threads/security-fi…	vendor-advisorypatch
https://xenforo.com/community/threads/xenforo-2-3…	release-notes
https://bombobombone.github.io/posts/cve-2026-73314/	technical-description
https://github.com/BomboBombone/CVE-2026-73314	exploit
https://www.vulncheck.com/advisories/xenforo-sign…	third-party-advisory

Impacted products

1 product

Vendor	Product	Version	CPE status
XenForo	XenForo	Affected: 0 , < 2.3.13 (semver)	guessed

Date Public

2026-09-07 00:00

Credits

Marco Paciaroni (BomboBombone) VulnCheck

Show details on NVD website

JSON

To clipboard

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FKIE_CVE-2026-73314

Vulnerability from fkie_nvd - Published: 2026-09-08 14:17 - Updated: 2026-09-11 20:31

Severity

7.5 (High) - CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N

Summary

References

URL	Tags
disclosure@vulncheck.com	https://bombobombone.github.io/posts/cve-2026-73314/	Exploit, Third Party Advisory
disclosure@vulncheck.com	https://github.com/BomboBombone/CVE-2026-73314	Exploit, Third Party Advisory
disclosure@vulncheck.com	https://www.vulncheck.com/advisories/xenforo-signature-verification-bypass-via-paypal-rest-webhook	Third Party Advisory
disclosure@vulncheck.com	https://xenforo.com/community/threads/security-fixes-released-for-all-xenforo-and-media-gallery-versions-2-2-0-2-3-12.239856/	Release Notes
disclosure@vulncheck.com	https://xenforo.com/community/threads/xenforo-2-3-13-and-add-ons-released-includes-security-fixes.239857/	Release Notes

Impacted products

	Vendor	Product	Version
	xenforo	xenforo	*

JSON

To clipboard

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    }
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  "lastModified": "2026-09-11T20:31:16.703",
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          "version": "4.0",
          "vulnAvailabilityImpact": "NONE",
          "vulnConfidentialityImpact": "NONE",
          "vulnIntegrityImpact": "HIGH",
          "vulnerabilityResponseEffort": "NOT_DEFINED"
        },
        "source": "disclosure@vulncheck.com",
        "type": "Secondary"
      }
    ],
    "ssvcV203": [
      {
        "source": "134c704f-9b21-4f2e-91b3-4a467353bcc0",
        "ssvcData": {
          "id": "CVE-2026-73314",
          "options": [
            {
              "exploitation": "poc"
            },
            {
              "automatable": "yes"
            },
            {
              "technicalImpact": "partial"
            }
          ],
          "role": "CISA Coordinator",
          "timestamp": "2026-09-10T13:46:00.578050Z",
          "version": "2.0.3"
        }
      }
    ]
  },
  "published": "2026-09-08T14:17:25.640",
  "references": [
    {
      "source": "disclosure@vulncheck.com",
      "tags": [
        "Exploit",
        "Third Party Advisory"
      ],
      "url": "https://bombobombone.github.io/posts/cve-2026-73314/"
    },
    {
      "source": "disclosure@vulncheck.com",
      "tags": [
        "Exploit",
        "Third Party Advisory"
      ],
      "url": "https://github.com/BomboBombone/CVE-2026-73314"
    },
    {
      "source": "disclosure@vulncheck.com",
      "tags": [
        "Third Party Advisory"
      ],
      "url": "https://www.vulncheck.com/advisories/xenforo-signature-verification-bypass-via-paypal-rest-webhook"
    },
    {
      "source": "disclosure@vulncheck.com",
      "tags": [
        "Release Notes"
      ],
      "url": "https://xenforo.com/community/threads/security-fixes-released-for-all-xenforo-and-media-gallery-versions-2-2-0-2-3-12.239856/"
    },
    {
      "source": "disclosure@vulncheck.com",
      "tags": [
        "Release Notes"
      ],
      "url": "https://xenforo.com/community/threads/xenforo-2-3-13-and-add-ons-released-includes-security-fixes.239857/"
    }
  ],
  "sourceIdentifier": "disclosure@vulncheck.com",
  "vulnStatus": "Analyzed",
  "weaknesses": [
    {
      "description": [
        {
          "lang": "en",
          "value": "CWE-754"
        }
      ],
      "source": "disclosure@vulncheck.com",
      "type": "Secondary"
    }
  ]
}

GHSA-RQWM-9M4J-F7G3

Vulnerability from github – Published: 2026-09-08 15:31 – Updated: 2026-09-09 03:30

Details

Severity

7.5 (High)


                  
                    CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N

8.7 (High)


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

Show details on source website

JSON

To clipboard

{
  "affected": [],
  "aliases": [
    "CVE-2026-73314"
  ],
  "database_specific": {
    "cwe_ids": [
      "CWE-754"
    ],
    "github_reviewed": false,
    "github_reviewed_at": null,
    "nvd_published_at": "2026-09-08T14:17:25Z",
    "severity": "HIGH"
  },
  "details": "XenForo before 2.3.13 contains a signature verification logic error in the PayPal REST webhook handler that allows unauthenticated attackers to bypass payment signature validation by submitting a webhook request with an unsupported auth_algo header value. When the algorithm cannot be mapped to a supported hash function, the verification function incorrectly returns true instead of failing, causing the caller to treat the fabricated request as verified and process the payment event without a valid PayPal signature.",
  "id": "GHSA-rqwm-9m4j-f7g3",
  "modified": "2026-09-09T03:30:36Z",
  "published": "2026-09-08T15:31:55Z",
  "references": [
    {
      "type": "ADVISORY",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-73314"
    },
    {
      "type": "WEB",
      "url": "https://bombobombone.github.io/posts/cve-2026-73314"
    },
    {
      "type": "WEB",
      "url": "https://github.com/BomboBombone/CVE-2026-73314"
    },
    {
      "type": "WEB",
      "url": "https://www.vulncheck.com/advisories/xenforo-signature-verification-bypass-via-paypal-rest-webhook"
    },
    {
      "type": "WEB",
      "url": "https://xenforo.com/community/threads/security-fixes-released-for-all-xenforo-and-media-gallery-versions-2-2-0-2-3-12.239856"
    },
    {
      "type": "WEB",
      "url": "https://xenforo.com/community/threads/xenforo-2-3-13-and-add-ons-released-includes-security-fixes.239857"
    }
  ],
  "schema_version": "1.4.0",
  "severity": [
    {
      "score": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N",
      "type": "CVSS_V3"
    },
    {
      "score": "CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/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.
Browse all ATT&CK techniques and the vulnerabilities related to each.

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Vulnerabilities whose description is nearest to this one in the vector space of the CIRCL/vulnerability-attack-technique-biencoder model. This is a similarity search over the bi-encoder space (plain cosine), not a classification, and it has no measured accuracy.

Action not permitted

CVE-2026-73314 (GCVE-0-2026-73314)

FKIE_CVE-2026-73314

GHSA-RQWM-9M4J-F7G3

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