quic-go webtransport-go up to 0.9.x WT_CLOSE_SESSION allocation of resources

Summaryinfo

A vulnerability, which was classified as problematic, was found in quic-go webtransport-go up to 0.9.x. The affected element is an unknown function. Executing a manipulation of the argument WT_CLOSE_SESSION can lead to allocation of resources. This vulnerability is tracked as CVE-2026-21434. The attack can be launched remotely. No exploit exists. You should upgrade the affected component.

Detailsinfo

A vulnerability has been found in quic-go webtransport-go up to 0.9.x and classified as problematic. This vulnerability affects some unknown functionality. The manipulation of the argument WT_CLOSE_SESSION with an unknown input leads to a allocation of resources vulnerability. The CWE definition for the vulnerability is CWE-770. The product allocates a reusable resource or group of resources on behalf of an actor without imposing any restrictions on the size or number of resources that can be allocated, in violation of the intended security policy for that actor. As an impact it is known to affect availability. CVE summarizes:

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.

The advisory is available at github.com. This vulnerability was named CVE-2026-21434 since 12/29/2025. The exploitation appears to be easy. The attack can be initiated remotely. No form of authentication is required for a successful exploitation. Technical details are known, but there is no available exploit. This vulnerability is assigned to T1499 by the MITRE ATT&CK project.

Upgrading to version 0.10.0 eliminates this vulnerability. The upgrade is hosted for download at github.com.

If you want to get best quality of vulnerability data, you may have to visit VulDB.

Productinfo

Vendor

• quic-go

Name

• webtransport-go

Version

• 0.1
• 0.2
• 0.3
• 0.4
• 0.5
• 0.6
• 0.7
• 0.8
• 0.9

Website

• Product: https://github.com/quic-go/webtransport-go/

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