Vulnerability-Lookup

GHSA-PX4R-G4P3-HHQV

Vulnerability from github – Published: 2026-02-12 15:29 – Updated: 2026-02-12 22:07

Summary

webtransport-go: CloseWithError can block indefinitely

Details

Summary

An attacker can cause a denial of service in webtransport-go by preventing or indefinitely delaying WebTransport session closure. A malicious peer can withhold QUIC flow control credit on the CONNECT stream, blocking transmission of the WT_CLOSE_SESSION capsule and causing the close operation to hang.

Details

WebTransport over HTTP/3 signals session termination by sending a WT_CLOSE_SESSION capsule on the CONNECT stream. The capsule is only needed to transmit a reason phrase and an error code to the peer. After the capsule is sent, the CONNECT stream is closed. In affected versions, the closure procedure blocked indefinitely while waiting for sufficient QUIC flow control credit from the peer. A malicious peer can withhold this credit, preventing the capsule from being sent.

The Fix

webtransport-go now attempts to send the WT_CLOSE_SESSION capsule with a short deadline. If the capsule cannot be sent within this deadline, the CONNECT stream is reset instead. This closes the WebTransport session promptly without transmitting the optional error details. This prevents indefinite blocking on session closure.

Severity ?

5.3 (Medium)


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

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{
  "affected": [
    {
      "database_specific": {
        "last_known_affected_version_range": "\u003c= 0.9.0"
      },
      "package": {
        "ecosystem": "Go",
        "name": "github.com/quic-go/webtransport-go"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "0"
            },
            {
              "fixed": "0.10.0"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ]
    }
  ],
  "aliases": [
    "CVE-2026-21435"
  ],
  "database_specific": {
    "cwe_ids": [
      "CWE-400"
    ],
    "github_reviewed": true,
    "github_reviewed_at": "2026-02-12T15:29:01Z",
    "nvd_published_at": "2026-02-12T19:15:51Z",
    "severity": "MODERATE"
  },
  "details": "## Summary\nAn attacker can cause a denial of service in webtransport-go by preventing or indefinitely delaying WebTransport session closure. A malicious peer can withhold QUIC flow control credit on the CONNECT stream, blocking transmission of the WT_CLOSE_SESSION capsule and causing the close operation to hang.\n\n## Details\nWebTransport over HTTP/3 signals session termination by sending a WT_CLOSE_SESSION capsule on the CONNECT stream. The capsule is only needed to transmit a reason phrase and an error code to the peer. After the capsule is sent, the CONNECT stream is closed.\nIn affected versions, the closure procedure blocked indefinitely while waiting for sufficient QUIC flow control credit from the peer. A malicious peer can withhold this credit, preventing the capsule from being sent.\n\n## The Fix\nwebtransport-go now attempts to send the WT_CLOSE_SESSION capsule with a short deadline. If the capsule cannot be sent within this deadline, the CONNECT stream is reset instead. This closes the WebTransport session promptly without transmitting the optional error details.\nThis prevents indefinite blocking on session closure.",
  "id": "GHSA-px4r-g4p3-hhqv",
  "modified": "2026-02-12T22:07:35Z",
  "published": "2026-02-12T15:29:01Z",
  "references": [
    {
      "type": "WEB",
      "url": "https://github.com/quic-go/webtransport-go/security/advisories/GHSA-px4r-g4p3-hhqv"
    },
    {
      "type": "ADVISORY",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-21435"
    },
    {
      "type": "PACKAGE",
      "url": "https://github.com/quic-go/webtransport-go"
    },
    {
      "type": "WEB",
      "url": "https://github.com/quic-go/webtransport-go/releases/tag/v0.10.0"
    }
  ],
  "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:L",
      "type": "CVSS_V3"
    }
  ],
  "summary": "webtransport-go: CloseWithError can block indefinitely"
}

CVE-2026-21435 (GCVE-0-2026-21435)

Vulnerability from cvelistv5 – Published: 2026-02-12 18:22 – Updated: 2026-02-17 15:36

Title

webtransport-go CloseWithError can block indefinitely

Summary

webtransport-go is an implementation of the WebTransport protocol. Prior to v0.10.0, an attacker can cause a denial of service in webtransport-go by preventing or indefinitely delaying WebTransport session closure. A malicious peer can withhold QUIC flow control credit on the CONNECT stream, blocking transmission of the WT_CLOSE_SESSION capsule and causing the close operation to hang. This vulnerability is fixed in v0.10.0.

Severity ?

5.3 (Medium)


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

CWE

CWE-400 - Uncontrolled Resource Consumption

Assigner

GitHub_M

References

URL

Tags

	https://github.com/quic-go/webtransport-go/securi…	x_refsource_CONFIRM
	https://github.com/quic-go/webtransport-go/releas…	x_refsource_MISC

Impacted products

	Vendor	Product	Version
	quic-go	webtransport-go	Affected: < 0.10.0

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JSON

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{
  "containers": {
    "adp": [
      {
        "metrics": [
          {
            "other": {
              "content": {
                "id": "CVE-2026-21435",
                "options": [
                  {
                    "Exploitation": "none"
                  },
                  {
                    "Automatable": "yes"
                  },
                  {
                    "Technical Impact": "partial"
                  }
                ],
                "role": "CISA Coordinator",
                "timestamp": "2026-02-17T15:35:59.809407Z",
                "version": "2.0.3"
              },
              "type": "ssvc"
            }
          }
        ],
        "providerMetadata": {
          "dateUpdated": "2026-02-17T15:36:08.731Z",
          "orgId": "134c704f-9b21-4f2e-91b3-4a467353bcc0",
          "shortName": "CISA-ADP"
        },
        "title": "CISA ADP Vulnrichment"
      }
    ],
    "cna": {
      "affected": [
        {
          "product": "webtransport-go",
          "vendor": "quic-go",
          "versions": [
            {
              "status": "affected",
              "version": "\u003c 0.10.0"
            }
          ]
        }
      ],
      "descriptions": [
        {
          "lang": "en",
          "value": "webtransport-go is an implementation of the WebTransport protocol. Prior to v0.10.0, an attacker can cause a denial of service in webtransport-go by preventing or indefinitely delaying WebTransport session closure. A malicious peer can withhold QUIC flow control credit on the CONNECT stream, blocking transmission of the WT_CLOSE_SESSION capsule and causing the close operation to hang. This vulnerability is fixed in v0.10.0."
        }
      ],
      "metrics": [
        {
          "cvssV3_1": {
            "attackComplexity": "LOW",
            "attackVector": "NETWORK",
            "availabilityImpact": "LOW",
            "baseScore": 5.3,
            "baseSeverity": "MEDIUM",
            "confidentialityImpact": "NONE",
            "integrityImpact": "NONE",
            "privilegesRequired": "NONE",
            "scope": "UNCHANGED",
            "userInteraction": "NONE",
            "vectorString": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L",
            "version": "3.1"
          }
        }
      ],
      "problemTypes": [
        {
          "descriptions": [
            {
              "cweId": "CWE-400",
              "description": "CWE-400: Uncontrolled Resource Consumption",
              "lang": "en",
              "type": "CWE"
            }
          ]
        }
      ],
      "providerMetadata": {
        "dateUpdated": "2026-02-12T18:24:49.233Z",
        "orgId": "a0819718-46f1-4df5-94e2-005712e83aaa",
        "shortName": "GitHub_M"
      },
      "references": [
        {
          "name": "https://github.com/quic-go/webtransport-go/security/advisories/GHSA-px4r-g4p3-hhqv",
          "tags": [
            "x_refsource_CONFIRM"
          ],
          "url": "https://github.com/quic-go/webtransport-go/security/advisories/GHSA-px4r-g4p3-hhqv"
        },
        {
          "name": "https://github.com/quic-go/webtransport-go/releases/tag/v0.10.0",
          "tags": [
            "x_refsource_MISC"
          ],
          "url": "https://github.com/quic-go/webtransport-go/releases/tag/v0.10.0"
        }
      ],
      "source": {
        "advisory": "GHSA-px4r-g4p3-hhqv",
        "discovery": "UNKNOWN"
      },
      "title": "webtransport-go CloseWithError can block indefinitely"
    }
  },
  "cveMetadata": {
    "assignerOrgId": "a0819718-46f1-4df5-94e2-005712e83aaa",
    "assignerShortName": "GitHub_M",
    "cveId": "CVE-2026-21435",
    "datePublished": "2026-02-12T18:22:58.098Z",
    "dateReserved": "2025-12-29T03:00:29.275Z",
    "dateUpdated": "2026-02-17T15:36:08.731Z",
    "state": "PUBLISHED"
  },
  "dataType": "CVE_RECORD",
  "dataVersion": "5.2"
}

Sightings

Author	Source	Type	Date

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.

Action not permitted

GHSA-PX4R-G4P3-HHQV

Summary

Details

The Fix

CVE-2026-21435 (GCVE-0-2026-21435)

Tags

Sightings

Nomenclature