Vulnerability-Lookup

CVE-2026-56853 (GCVE-0-2026-56853)

Vulnerability from cvelistv5 – Published: 2026-08-13 21:58 – Updated: 2026-08-14 15:23

Title

Apply ReadHeaderTimeout when doing unencrypted HTTP/2 check in net/http

Summary

When a server is configured to support unencrypted HTTP/2, it reads a few bytes from each new connection to see if they contain the HTTP/2 client preface. ReadHeaderTimeout is unexpectedly not being applied when doing this.

Severity

7.5 (High)


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

SSVC

Exploitation: none Automatable: yes Technical Impact: partial

CISA Coordinator · CISA-ADP (v2.0.3)

Decision recorded 2026-08-14 15:22 UTC

CWE

CWE-770 - Allocation of Resources Without Limits or Throttling

Assigner

References

4 references

URL	Tags
https://go.dev/issue/80205
https://go.dev/cl/795540
https://groups.google.com/g/golang-announce/c/94p…
https://pkg.go.dev/vuln/GO-2026-6089

Impacted products

1 product

Vendor	Product	Version
Go standard library	net/http	Affected: 0 , < 1.25.13 (semver) Affected: 1.26.0-0 , < 1.26.6 (semver) Affected: 1.27.0-0 , < 1.27.0-rc.3 (semver)

Show details on NVD website

JSON

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{
  "containers": {
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        "metrics": [
          {
            "cvssV3_1": {
              "attackComplexity": "LOW",
              "attackVector": "NETWORK",
              "availabilityImpact": "HIGH",
              "baseScore": 7.5,
              "baseSeverity": "HIGH",
              "confidentialityImpact": "NONE",
              "integrityImpact": "NONE",
              "privilegesRequired": "NONE",
              "scope": "UNCHANGED",
              "userInteraction": "NONE",
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            }
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              "content": {
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                  },
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                  }
                ],
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                "timestamp": "2026-08-14T15:22:45.475320Z",
                "version": "2.0.3"
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            }
          }
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        ],
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          "shortName": "CISA-ADP"
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            },
            {
              "name": "ListenAndServe"
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            {
              "name": "ListenAndServeTLS"
            },
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            },
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              "version": "1.27.0-0",
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      ],
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        }
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        },
        {
          "url": "https://pkg.go.dev/vuln/GO-2026-6089"
        }
      ],
      "title": "Apply ReadHeaderTimeout when doing unencrypted HTTP/2 check in net/http"
    }
  },
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    "dateReserved": "2026-06-23T15:10:49.352Z",
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    "state": "PUBLISHED"
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    "redhat_vex": {
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      "initial_release_date": "2026-08-13T21:58:53.092000+00:00",
      "product_status:known_affected": "432",
      "product_status:known_not_affected": "2",
      "source": "Red Hat CSAF VEX",
      "status": "final",
      "title": "net/http: golang: Go net/http: Unencrypted HTTP/2 connections vulnerable to Denial of Service",
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GHSA-XPHW-4F88-5F39

Vulnerability from github – Published: 2026-08-14 00:31 – Updated: 2026-08-14 18:31

Details

Severity

7.5 (High)


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

Show details on source website

JSON

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{
  "affected": [],
  "aliases": [
    "CVE-2026-56853"
  ],
  "database_specific": {
    "cwe_ids": [
      "CWE-770"
    ],
    "github_reviewed": false,
    "github_reviewed_at": null,
    "nvd_published_at": "2026-08-13T22:17:22Z",
    "severity": "HIGH"
  },
  "details": "When a server is configured to support unencrypted HTTP/2, it reads a few bytes from each new connection to see if they contain the HTTP/2 client preface. ReadHeaderTimeout is unexpectedly not being applied when doing this.",
  "id": "GHSA-xphw-4f88-5f39",
  "modified": "2026-08-14T18:31:33Z",
  "published": "2026-08-14T00:31:59Z",
  "references": [
    {
      "type": "ADVISORY",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-56853"
    },
    {
      "type": "WEB",
      "url": "https://go.dev/cl/795540"
    },
    {
      "type": "WEB",
      "url": "https://go.dev/issue/80205"
    },
    {
      "type": "WEB",
      "url": "https://groups.google.com/g/golang-announce/c/94pEornpRlI"
    },
    {
      "type": "WEB",
      "url": "https://pkg.go.dev/vuln/GO-2026-6089"
    }
  ],
  "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",
      "type": "CVSS_V3"
    }
  ]
}

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-2026-56853 (GCVE-0-2026-56853)

GHSA-XPHW-4F88-5F39

Tags

Sightings

Nomenclature