Vulnerability · Published Feb 12, 2026 · Assigned by GitHub_M
CVE-2026-21434webtransport-go affected by Memory Exhaustion Attack due to Missing Length Check in WT_CLOSE_SESSION Capsule
Medium 5.3
In plain English
A medium-severity resource allocation without limits in webtransport-go from quic-go. There are no confirmed reports of exploitation so far. The chance it is exploited in the next 30 days is estimated at 0.5% (higher than 40% of all known vulnerabilities). Fixed versions are available - upgrade the affected package.
Official 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.
Affected packages & fixed versions
| Ecosystem | Package | Fixed in | Advisory |
|---|---|---|---|
| Go | github.com/marten-seemann/webtransport-go | no fix listed | GO-2026-4485 |
| Go | github.com/quic-go/webtransport-go | 0.10.0 | GHSA-g6x7-jq8p-6q9q |
| Go | github.com/quic-go/webtransport-go | 0.10.0 | GO-2026-4485 |
Affected products (as reported)
| Vendor | Product | Versions |
|---|---|---|
| quic-go | webtransport-go | < 0.10.0 |
Weakness: CWE-770 · Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L
References
- https://github.com/quic-go/webtransport-go/security/advisories/GHSA-g6x7-jq8p-6q9q x_refsource_CONFIRM
- https://github.com/quic-go/webtransport-go/releases/tag/v0.10.0 x_refsource_MISC