CVE-2026-21434
webtransport-go affected by Memory Exhaustion Attack due to Missing Length Check in WT_CLOSE_SESSION Capsule
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.
INFO
Published Date :
Feb. 12, 2026, 7:15 p.m.
Last Modified :
Feb. 19, 2026, 10:53 p.m.
Remotely Exploit :
Yes !
Source :
[email protected]
CVSS Scores
| Score | Version | Severity | Vector | Exploitability Score | Impact Score | Source |
|---|---|---|---|---|---|---|
| CVSS 3.1 | MEDIUM | [email protected] | ||||
| CVSS 3.1 | HIGH | [email protected] |
Solution
- Update webtransport-go to version 0.10.0 or later.
- Apply patches if available for older versions.
- Monitor memory usage for anomalous spikes.
References to Advisories, Solutions, and Tools
Here, you will find a curated list of external links that provide in-depth
information, practical solutions, and valuable tools related to
CVE-2026-21434.
| URL | Resource |
|---|---|
| https://github.com/quic-go/webtransport-go/releases/tag/v0.10.0 | Product Release Notes |
| https://github.com/quic-go/webtransport-go/security/advisories/GHSA-g6x7-jq8p-6q9q | Vendor Advisory |
CWE - Common Weakness Enumeration
While CVE identifies
specific instances of vulnerabilities, CWE categorizes the common flaws or
weaknesses that can lead to vulnerabilities. CVE-2026-21434 is
associated with the following CWEs:
Common Attack Pattern Enumeration and Classification (CAPEC)
Common Attack Pattern Enumeration and Classification
(CAPEC)
stores attack patterns, which are descriptions of the common attributes and
approaches employed by adversaries to exploit the CVE-2026-21434
weaknesses.
We scan GitHub repositories to detect new proof-of-concept exploits. Following list is a collection of public exploits and proof-of-concepts, which have been published on GitHub (sorted by the most recently updated).
Results are limited to the first 15 repositories due to potential performance issues.
The following list is the news that have been mention
CVE-2026-21434 vulnerability anywhere in the article.
The following table lists the changes that have been made to the
CVE-2026-21434 vulnerability over time.
Vulnerability history details can be useful for understanding the evolution of a vulnerability, and for identifying the most recent changes that may impact the vulnerability's severity, exploitability, or other characteristics.
-
Initial Analysis by [email protected]
Feb. 19, 2026
Action Type Old Value New Value Added CVSS V3.1 AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H Added CPE Configuration OR *cpe:2.3:a:quic-go:webtransport-go:*:*:*:*:*:go:*:* versions from (including) 0.3.0 up to (excluding) 0.10.0 Added Reference Type GitHub, Inc.: https://github.com/quic-go/webtransport-go/releases/tag/v0.10.0 Types: Product, Release Notes Added Reference Type GitHub, Inc.: https://github.com/quic-go/webtransport-go/security/advisories/GHSA-g6x7-jq8p-6q9q Types: Vendor Advisory -
New CVE Received by [email protected]
Feb. 12, 2026
Action Type Old Value New Value 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. Added CVSS V3.1 AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L Added CWE CWE-770 Added Reference https://github.com/quic-go/webtransport-go/releases/tag/v0.10.0 Added Reference https://github.com/quic-go/webtransport-go/security/advisories/GHSA-g6x7-jq8p-6q9q