What’s Vulnerable › Vulnerabilities

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

• Severity: medium (CVSS 5.3 v3.1)
• Exploited in the wild: not listed in CISA KEV
• EPSS: 0.5% probability of exploitation in the next 30 days
• Public exploit or detection template: none known
• Published: 2026-09-14 · updated 2026-09-30
• Weakness: CWE-770

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 products

• quic-go webtransport-go: before 0.11.1

References

• https://github.com/quic-go/webtransport-go/commit/3aecd11736579530ff067651c30a543eb0b4b8c4
• https://github.com/quic-go/webtransport-go/pull/290
• https://github.com/quic-go/webtransport-go/releases/tag/v0.11.1
• https://github.com/quic-go/webtransport-go/security/advisories/GHSA-g35j-m5xg-vh3q

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