webtransport-go is an implementation of the WebTransport protocol. From 0.3.0 to 0.9.0, an attacker can cause excessive memory consumption in webtransport-go's session implementation by sending a WT_CLOSE_SESSION capsule containing an excessively large Application Error Message. The implementation does not enforce the draft-mandated limit of 1024 bytes on this field, allowing a peer to send an arbitrarily large message payload that is fully read and stored in memory. This allows an attacker to consume an arbitrary amount of memory. The attacker must transmit the full payload to achieve the memory consumption, but the lack of any upper bound makes large-scale attacks feasible given sufficient bandwidth. This vulnerability is fixed in 0.10.0.
Advisories
Source ID Title
Github GHSA Github GHSA GHSA-g6x7-jq8p-6q9q webtransport-go: Memory Exhaustion Attack due to Missing Length Check in WT_CLOSE_SESSION Capsule
Fixes

Solution

No solution given by the vendor.


Workaround

No workaround given by the vendor.

History

Thu, 12 Feb 2026 19:30:00 +0000

Type Values Removed Values Added
Metrics ssvc

{'options': {'Automatable': 'yes', 'Exploitation': 'none', 'Technical Impact': 'partial'}, 'version': '2.0.3'}


Thu, 12 Feb 2026 18:45:00 +0000

Type Values Removed Values Added
Description webtransport-go is an implementation of the WebTransport protocol. From 0.3.0 to 0.9.0, an attacker can cause excessive memory consumption in webtransport-go's session implementation by sending a WT_CLOSE_SESSION capsule containing an excessively large Application Error Message. The implementation does not enforce the draft-mandated limit of 1024 bytes on this field, allowing a peer to send an arbitrarily large message payload that is fully read and stored in memory. This allows an attacker to consume an arbitrary amount of memory. The attacker must transmit the full payload to achieve the memory consumption, but the lack of any upper bound makes large-scale attacks feasible given sufficient bandwidth. This vulnerability is fixed in 0.10.0.
Title webtransport-go affected by Memory Exhaustion Attack due to Missing Length Check in WT_CLOSE_SESSION Capsule
Weaknesses CWE-770
References
Metrics cvssV3_1

{'score': 5.3, 'vector': 'CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L'}


Projects

Sign in to view the affected projects.

cve-icon MITRE

Status: PUBLISHED

Assigner: GitHub_M

Published:

Updated: 2026-02-12T18:45:58.158Z

Reserved: 2025-12-29T03:00:29.275Z

Link: CVE-2026-21434

cve-icon Vulnrichment

Updated: 2026-02-12T18:45:53.125Z

cve-icon NVD

Status : Received

Published: 2026-02-12T19:15:51.333

Modified: 2026-02-12T19:15:51.333

Link: CVE-2026-21434

cve-icon Redhat

No data.

cve-icon OpenCVE Enrichment

No data.

Weaknesses