CVE-2026-78661 (GCVE-0-2026-78661)

Vulnerability from cvelistv5 – Published: 2026-10-27 21:38 – Updated: 2026-10-27 21:38
VLAI
Title
Avoid quadratic complexity when coalescing text nodes in html in golang.org/x/net
Summary
When coalescing adjacent text nodes in addText and fosterParent, appending to an existing TextNode's Data via string concatenation (n.Data += text) reallocated and copied the accumulated string on every token. Inputs containing many short text runs separated by ignored end tags (such as "a</x>") caused O(n^2) allocations and byte copies. Accumulate coalesced text in per-node byte slices during parsing and materialize Data strings once at the end of parse.
Severity
No CVSS data available.
CWE
  • CWE-407 - Inefficient Algorithmic Complexity
Assigner
Go CNA under the Google root
CNA scorecard E 42/100 over 76 records in the last 180 days details
References
Impacted products
Vendor Product Version CPE status
golang.org/x/net golang.org/x/net/html Affected: 0 , < 0.62.0 (semver)
guessed Create a notification for this product.
Credits
Markus Magnuson
Show details on NVD website
To clipboard 

{
  "containers": {
    "cna": {
      "affected": [
        {
          "collectionURL": "https://pkg.go.dev",
          "defaultStatus": "unaffected",
          "packageName": "golang.org/x/net/html",
          "product": "golang.org/x/net/html",
          "programRoutines": [
            {
              "name": "parser.addText"
            },
            {
              "name": "parser.fosterParent"
            },
            {
              "name": "parser.parse"
            },
            {
              "name": "Parse"
            },
            {
              "name": "ParseFragment"
            },
            {
              "name": "ParseFragmentWithOptions"
            },
            {
              "name": "ParseWithOptions"
            }
          ],
          "vendor": "golang.org/x/net",
          "versions": [
            {
              "lessThan": "0.62.0",
              "status": "affected",
              "version": "0",
              "versionType": "semver"
            }
          ]
        }
      ],
      "credits": [
        {
          "lang": "en",
          "value": "Markus Magnuson"
        }
      ],
      "descriptions": [
        {
          "lang": "en",
          "value": "When coalescing adjacent text nodes in addText and fosterParent, appending to an existing TextNode\u0027s Data via string concatenation (n.Data += text) reallocated and copied the accumulated string on every token. Inputs containing many short text runs separated by ignored end tags (such as \"a\u003c/x\u003e\") caused O(n^2) allocations and byte copies. Accumulate coalesced text in per-node byte slices during parsing and materialize Data strings once at the end of parse."
        }
      ],
      "problemTypes": [
        {
          "descriptions": [
            {
              "description": "CWE-407: Inefficient Algorithmic Complexity",
              "lang": "en"
            }
          ]
        }
      ],
      "providerMetadata": {
        "dateUpdated": "2026-10-27T21:38:56.517Z",
        "orgId": "1bb62c36-49e3-4200-9d77-64a1400537cc",
        "shortName": "Go"
      },
      "references": [
        {
          "url": "https://go.dev/cl/849365"
        },
        {
          "url": "https://go.dev/issue/82224"
        },
        {
          "url": "https://groups.google.com/g/golang-announce/c/sqrs2vTx_Xs"
        },
        {
          "url": "https://pkg.go.dev/vuln/GO-2026-6860"
        }
      ],
      "title": "Avoid quadratic complexity when coalescing text nodes in html in golang.org/x/net"
    }
  },
  "cveMetadata": {
    "assignerOrgId": "1bb62c36-49e3-4200-9d77-64a1400537cc",
    "assignerShortName": "Go",
    "cveId": "CVE-2026-78661",
    "datePublished": "2026-10-27T21:38:56.517Z",
    "dateReserved": "2026-08-24T23:36:15.738Z",
    "dateUpdated": "2026-10-27T21:38:56.517Z",
    "state": "PUBLISHED"
  },
  "dataType": "CVE_RECORD",
  "dataVersion": "5.2",
  "vulnerability-lookup:meta": {
    "epss": {
      "cve": "CVE-2026-78661",
      "date": "2026-11-01",
      "epss": "0.00185",
      "percentile": "0.08063"
    },
    "microsoft_vex": {
      "current_release_date": "2026-10-31T01:07:15.000Z",
      "cve": "CVE-2026-78661",
      "id": "msrc_CVE-2026-78661",
      "initial_release_date": "2026-10-31T01:07:15.000Z",
      "product_status:under_investigation": "24",
      "source": "Microsoft CSAF VEX",
      "status": "final",
      "title": "Avoid quadratic complexity when coalescing text nodes in html in golang.org/x/net",
      "url": "https://msrc.microsoft.com/csaf/vex/2026/msrc_cve-2026-78661.json",
      "version": "1"
    },
    "nvd": {
      "cve": {
        "affected": [
          {
            "affectedData": [
              {
                "collectionURL": "https://pkg.go.dev",
                "defaultStatus": "unaffected",
                "packageName": "golang.org/x/net/html",
                "product": "golang.org/x/net/html",
                "programRoutines": [
                  {
                    "name": "parser.addText"
                  },
                  {
                    "name": "parser.fosterParent"
                  },
                  {
                    "name": "parser.parse"
                  },
                  {
                    "name": "Parse"
                  },
                  {
                    "name": "ParseFragment"
                  },
                  {
                    "name": "ParseFragmentWithOptions"
                  },
                  {
                    "name": "ParseWithOptions"
                  }
                ],
                "vendor": "golang.org/x/net",
                "versions": [
                  {
                    "lessThan": "0.62.0",
                    "status": "affected",
                    "version": "0",
                    "versionType": "semver"
                  }
                ]
              }
            ],
            "source": "security@golang.org"
          }
        ],
        "cveTags": [],
        "descriptions": [
          {
            "lang": "en",
            "value": "When coalescing adjacent text nodes in addText and fosterParent, appending to an existing TextNode\u0027s Data via string concatenation (n.Data += text) reallocated and copied the accumulated string on every token. Inputs containing many short text runs separated by ignored end tags (such as \"a\u003c/x\u003e\") caused O(n^2) allocations and byte copies. Accumulate coalesced text in per-node byte slices during parsing and materialize Data strings once at the end of parse."
          }
        ],
        "id": "CVE-2026-78661",
        "lastModified": "2026-10-28T15:24:56.033",
        "metrics": {},
        "published": "2026-10-27T22:18:05.930",
        "references": [
          {
            "source": "security@golang.org",
            "url": "https://go.dev/cl/849365"
          },
          {
            "source": "security@golang.org",
            "url": "https://go.dev/issue/82224"
          },
          {
            "source": "security@golang.org",
            "url": "https://groups.google.com/g/golang-announce/c/sqrs2vTx_Xs"
          },
          {
            "source": "security@golang.org",
            "url": "https://pkg.go.dev/vuln/GO-2026-6860"
          }
        ],
        "sourceIdentifier": "security@golang.org",
        "vulnStatus": "Deferred"
      }
    }
  }
}



Log in or create an account to share your comment.




Tags
Taxonomy of the tags.




Drag nodes to arrange them. Double-click a related vulnerability to open it, or a source to visit its link. The Physics button on the left tunes the layout and the simulation; the legend at the bottom left hides or shows nodes by kind and by sighting type.

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.
Vulnerability timeline

Sightings and recorded dates, grouped by day · UTC

JSON

Loading timeline…




    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.