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Vulnerability · Published Sep 14, 2026 · Assigned by GitHub_M

CVE-2026-57497webtransport-go: Memory Exhaustion Attack due to Buffering of Unknown Capsules

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 45% of all known vulnerabilities). Fixed versions are available - upgrade the affected package.

Severity (CVSS 3.1)5.3Medium
Exploit odds (30 days)0.5%top 55.4% of all CVEs
Exploited in the wildNo reportsCISA SSVC: none
Attack toolingNoneno public tooling known

Official description

webtransport-go is an implementation of the WebTransport protocol. Prior to 0.11.1, Session.parseNextCapsule() in session.go skips an unknown WebTransport capsule on the HTTP/3 request stream by calling io.ReadAll on the capsule reader, retaining the complete declared capsule body in memory. A malicious peer can send a large unknown capsule and cause a client or server to allocate memory for the full payload; QUIC flow control does not bound the total retained allocation because reading advances the flow-control window while the received bytes remain in memory. The resulting memory and resource exhaustion can disrupt or crash the affected process. This issue is fixed in version 0.11.1.

Affected packages & fixed versions

EcosystemPackageFixed inAdvisory
Gogithub.com/quic-go/webtransport-go0.11.1GHSA-g35j-m5xg-vh3q
Gogithub.com/quic-go/webtransport-go0.11.1GO-2026-6099

Affected products (as reported)

VendorProductVersions
quic-go webtransport-go < 0.11.1

Weakness: CWE-770 · Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L

References