Vulnerability-Lookup

GHSA-VMV3-WVJP-WQPJ

Vulnerability from github – Published: 2026-11-10 23:20 – Updated: 2026-11-10 23:20

Summary

Microsoft Security Advisory CVE-2026-118747 - .NET Denial of Service Vulnerability

Details

Executive summary

Microsoft is releasing this security advisory to provide information about a vulnerability in .NET. This advisory provides guidance on updating affected applications and components.

Colliding CBOR map keys can hash-flood uniqueness checks; the fix uses seeded Marvin hashing.

Announcement

Announcement for this issue can be found at https://github.com/dotnet/announcements/issues/501

CVSS Details

Version: 3.1
Severity: High
Score: 7.5 (base score)
Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H/E:U/RL:O/RC:C
Weakness: CWE-407

Affected Platforms

Platforms: Any supported OS
Architectures: All

Affected Packages

The tables list affected package versions and fixed versions. These are independently versioned NuGet packages, not runtime patch versions.

8.0 - standalone packages

Package	Affected version	Patched version
System.Formats.Cbor	>= 8.0.0-0, < 8.0.2	8.0.2

9.0 - standalone packages

Package	Affected version	Patched version
System.Formats.Cbor	>= 9.0.0-0, < 9.0.24	9.0.24

Update 9.0 applications to System.Formats.Cbor 9.0.24; 9.0.23 is not a fix. The fixed 10.0.15 package, which includes a net9.0 target, remains an alternative.

10.0 - standalone packages

Package	Affected version	Patched version
System.Formats.Cbor	>= 10.0.0-0, < 10.0.15	10.0.15

11.0 - standalone packages

Package	Affected version	Patched version
System.Formats.Cbor	>= 11.0.0-0, < 11.0.0	11.0.0

Advisory FAQ

How do I know if I am affected?

Check the application's System.Formats.Cbor package reference against the affected ranges above. Updating only the installed runtime does not update this independently referenced package.

How do I fix the issue?

Update each applicable package reference to its patched version listed above, then rebuild and redeploy the application. Updating only the installed runtime does not update an application's standalone package references.

Other Information

Reporting Security Issues

If you have found a potential security issue in a supported version of .NET, please report it to the Microsoft Security Response Center (MSRC) via the MSRC Researcher Portal. Further information can be found in the MSRC Report an Issue FAQ.

Security reports made through MSRC may qualify for the Microsoft .NET Bounty. Details of the Microsoft .NET Bounty Program including terms and conditions are at https://aka.ms/corebounty.

Support

You can ask questions about this issue on GitHub in the .NET GitHub organization. The main repos are located at https://github.com/dotnet/runtime. The Announcements repo (https://github.com/dotnet/Announcements) will contain this bulletin as an issue and will include a link to a discussion issue. You can ask questions in the linked discussion issue.

Disclaimer

The information provided in this advisory is provided "as is" without warranty of any kind. Microsoft disclaims all warranties, either express or implied, including the warranties of merchantability and fitness for a particular purpose. In no event shall Microsoft Corporation or its suppliers be liable for any damages whatsoever including direct, indirect, incidental, consequential, loss of business profits or special damages, even if Microsoft Corporation or its suppliers have been advised of the possibility of such damages. Some states do not allow the exclusion or limitation of liability for consequential or incidental damages so the foregoing limitation may not apply.

External Links

CVE-2026-118747

Acknowledgements

Anonymous

Revisions

V1.0 (November 10, 2026): Advisory published.

Severity

7.5 (High)


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

Show details on source website

JSON

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{
  "affected": [
    {
      "package": {
        "ecosystem": "NuGet",
        "name": "System.Formats.Cbor"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "8.0.0-0"
            },
            {
              "fixed": "8.0.2"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ]
    },
    {
      "package": {
        "ecosystem": "NuGet",
        "name": "System.Formats.Cbor"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "9.0.0-0"
            },
            {
              "fixed": "9.0.24"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ]
    },
    {
      "package": {
        "ecosystem": "NuGet",
        "name": "System.Formats.Cbor"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "10.0.0-0"
            },
            {
              "fixed": "10.0.15"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ]
    },
    {
      "package": {
        "ecosystem": "NuGet",
        "name": "System.Formats.Cbor"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "11.0.0-0"
            },
            {
              "fixed": "11.0.0"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ]
    }
  ],
  "aliases": [
    "CVE-2026-118747"
  ],
  "database_specific": {
    "cwe_ids": [
      "CWE-407"
    ],
    "github_reviewed": true,
    "github_reviewed_at": "2026-11-10T23:20:27Z",
    "nvd_published_at": "2026-11-10T19:19:51Z",
    "severity": "MODERATE"
  },
  "details": "## Executive summary\n\nMicrosoft is releasing this security advisory to provide information about a vulnerability in .NET. This advisory provides guidance on updating affected applications and components.\n\nColliding CBOR map keys can hash-flood uniqueness checks; the fix uses seeded Marvin hashing.\n\n## Announcement\n\nAnnouncement for this issue can be found at https://github.com/dotnet/announcements/issues/501\n\n## CVSS Details\n\n- **Version:** 3.1\n- **Severity:** High\n- **Score:** 7.5 (base score)\n- **Vector:** `CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H/E:U/RL:O/RC:C`\n- **Weakness:** CWE-407\n\n## Affected Platforms\n\n- **Platforms:** Any supported OS\n- **Architectures:** All\n\n## \u003ca name=\"affected-packages\"\u003e\u003c/a\u003eAffected Packages\n\nThe tables list affected package versions and fixed versions. These are independently versioned NuGet packages, not runtime patch versions.\n\n### 8.0 - standalone packages\n\nPackage | Affected version | Patched version\n--- | --- | ---\n[System.Formats.Cbor](https://www.nuget.org/packages/System.Formats.Cbor) | \u003e= 8.0.0-0, \u003c 8.0.2 | 8.0.2\n\n### 9.0 - standalone packages\n\nPackage | Affected version | Patched version\n--- | --- | ---\n[System.Formats.Cbor](https://www.nuget.org/packages/System.Formats.Cbor) | \u003e= 9.0.0-0, \u003c 9.0.24 | 9.0.24\n\nUpdate 9.0 applications to System.Formats.Cbor 9.0.24; 9.0.23 is not a fix. The fixed 10.0.15 package, which includes a net9.0 target, remains an alternative.\n\n### 10.0 - standalone packages\n\nPackage | Affected version | Patched version\n--- | --- | ---\n[System.Formats.Cbor](https://www.nuget.org/packages/System.Formats.Cbor) | \u003e= 10.0.0-0, \u003c 10.0.15 | 10.0.15\n\n### 11.0 - standalone packages\n\nPackage | Affected version | Patched version\n--- | --- | ---\n[System.Formats.Cbor](https://www.nuget.org/packages/System.Formats.Cbor) | \u003e= 11.0.0-0, \u003c 11.0.0 | 11.0.0\n\n## Advisory FAQ\n\n### \u003ca name=\"how-affected\"\u003e\u003c/a\u003eHow do I know if I am affected?\n\nCheck the application\u0027s System.Formats.Cbor package reference against the affected ranges above. Updating only the installed runtime does not update this independently referenced package.\n\n### \u003ca name=\"how-fix\"\u003e\u003c/a\u003eHow do I fix the issue?\n\nUpdate each applicable package reference to its patched version listed above, then rebuild and redeploy the application. Updating only the installed runtime does not update an application\u0027s standalone package references.\n\n## Other Information\n\n### Reporting Security Issues\n\nIf you have found a potential security issue in a supported version of .NET, please report it to the Microsoft Security Response Center (MSRC) via the [MSRC Researcher Portal](https://msrc.microsoft.com/report/vulnerability/new). Further information can be found in the MSRC [Report an Issue FAQ](https://www.microsoft.com/msrc/faqs-report-an-issue).\n\nSecurity reports made through MSRC may qualify for the Microsoft .NET Bounty. Details of the Microsoft .NET Bounty Program including terms and conditions are at https://aka.ms/corebounty.\n\n### Support\n\nYou can ask questions about this issue on GitHub in the .NET GitHub organization. The main repos are located at https://github.com/dotnet/runtime. The Announcements repo (https://github.com/dotnet/Announcements) will contain this bulletin as an issue and will include a link to a discussion issue. You can ask questions in the linked discussion issue.\n\n### Disclaimer\n\nThe information provided in this advisory is provided \"as is\" without warranty of any kind. Microsoft disclaims all warranties, either express or implied, including the warranties of merchantability and fitness for a particular purpose. In no event shall Microsoft Corporation or its suppliers be liable for any damages whatsoever including direct, indirect, incidental, consequential, loss of business profits or special damages, even if Microsoft Corporation or its suppliers have been advised of the possibility of such damages. Some states do not allow the exclusion or limitation of liability for consequential or incidental damages so the foregoing limitation may not apply.\n\n### External Links\n\n[CVE-2026-118747](https://www.cve.org/CVERecord?id=CVE-2026-118747)\n\n### Acknowledgements\n\n- Anonymous\n\n### Revisions\n\nV1.0 (November 10, 2026): Advisory published.",
  "id": "GHSA-vmv3-wvjp-wqpj",
  "modified": "2026-11-10T23:20:27Z",
  "published": "2026-11-10T23:20:27Z",
  "references": [
    {
      "type": "WEB",
      "url": "https://github.com/dotnet/runtime/security/advisories/GHSA-vmv3-wvjp-wqpj"
    },
    {
      "type": "ADVISORY",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-118747"
    },
    {
      "type": "WEB",
      "url": "https://github.com/dotnet/announcements/issues/501"
    },
    {
      "type": "WEB",
      "url": "https://github.com/dotnet/runtime/issues/137281"
    },
    {
      "type": "WEB",
      "url": "https://github.com/dotnet/core/blob/main/release-notes/10.0/10.0.15/10.0.15.md"
    },
    {
      "type": "WEB",
      "url": "https://github.com/dotnet/core/blob/main/release-notes/11.0/11.0.0/11.0.0.md"
    },
    {
      "type": "WEB",
      "url": "https://github.com/dotnet/core/blob/main/release-notes/8.0/8.0.34/8.0.34.md"
    },
    {
      "type": "WEB",
      "url": "https://github.com/dotnet/core/blob/main/release-notes/9.0/9.0.23/9.0.23.md"
    },
    {
      "type": "PACKAGE",
      "url": "https://github.com/dotnet/runtime"
    },
    {
      "type": "WEB",
      "url": "https://github.com/dotnet/runtime/releases/tag/v10.0.15"
    },
    {
      "type": "WEB",
      "url": "https://github.com/dotnet/runtime/releases/tag/v11.0.0"
    },
    {
      "type": "WEB",
      "url": "https://github.com/dotnet/runtime/releases/tag/v8.0.2"
    },
    {
      "type": "WEB",
      "url": "https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-118747"
    }
  ],
  "schema_version": "1.4.0",
  "severity": [
    {
      "score": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H/E:U/RL:O/RC:C",
      "type": "CVSS_V3"
    }
  ],
  "summary": "Microsoft Security Advisory CVE-2026-118747 - .NET Denial of Service Vulnerability"
}

CVE-2026-118747 (GCVE-0-2026-118747)

Vulnerability from cvelistv5 – Published: 2026-11-10 18:21 – Updated: 2026-11-10 23:53

Title

.NET Denial of Service Vulnerability

Summary

Inefficient algorithmic complexity in .NET allows an unauthorized attacker to deny service over a network.

Severity

7.5 (High)


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

SSVC

Exploitation: none Automatable: yes Technical Impact: partial

CISA Coordinator · CISA-ADP (v2.0.3)

Decision recorded 2026-11-10 19:28 UTC

CWE

CWE-407 - Inefficient Algorithmic Complexity

Assigner

microsoft CNA under the mitre root

CNA scorecard B 82/100 over 4930 records in the last 180 days details

References

1 reference

URL	Tags
https://msrc.microsoft.com/update-guide/vulnerabi…	vendor-advisorypatch

Impacted products

1 product

Vendor	Product	Version
Microsoft	System.Formats.Cbor	Affected: 10.0.0 , < 9.0.24 (custom) cpe:2.3:a:microsoft:system.formats.cbor::::::::

Date Public

2026-11-10 16:00

Show details on NVD website

JSON

To clipboard

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    "adp": [
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        "metrics": [
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                "id": "CVE-2026-118747",
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                  },
                  {
                    "Technical Impact": "partial"
                  }
                ],
                "role": "CISA Coordinator",
                "timestamp": "2026-11-10T19:28:15.361512Z",
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          "shortName": "CISA-ADP"
        },
        "title": "CISA ADP Vulnrichment"
      }
    ],
    "cna": {
      "affected": [
        {
          "platforms": [
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          "product": "System.Formats.Cbor",
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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.

Vulnerability timeline

Sightings and recorded dates, grouped by day · UTC

Order JSON

How durations are calculated

Following the VTEM framework (Black Hat USA 2015), time to patch starts when the vendor or a coordinator was informed, total time to patch at discovery, and disclosure to patch at public disclosure; vendor response time runs from the report to its acknowledgement. Time to exploit and time unpatched start at the earliest discovery or report, falling back to public disclosure. Unpatched time ends at the first recorded patch, or the calculation time when no patch is recorded. Exploitation to patch shows the interval between those two events; a published proof of concept is a public exploit, not exploitation.

Each result shows its source dates. A negative interval means the end event came first; when date-only inputs leave the order open, the result says so. Date-only inputs are approximate. The earliest evidence wins: KEV report dates and sightings are labelled as such. Records describing another vulnerability are listed but never calculated from, and a PoC alone does not establish exploitation. Missing patch evidence does not prove that no patch exists. Filters below change the event list only.

Publication & reservation Sightings KEV catalogs Other timestamps

Loading timeline…

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.

Related by attack behaviour

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.

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