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

Exploitation

No confirmed exploitation recorded. Patch Next marks exploitation only from CISA KEV.

CVSS

5.3 · CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L

EPSS

• CVE-2026-57497: 0.52% estimated exploitation activity in the next 30 days; percentile 44.48 (FIRST EPSS, 2026-11-03). This is a model estimate, not proof of exploitation or customer exposure.

As published by the source; long descriptions are shortened.

Summary An attacker can cause excessive memory allocation in webtransport-go by sending an unknown WebTransport capsule with a large payload. The implementation skips unknown capsules by reading the entire capsule body into memory, instead of draining it without retaining the data. This can lead to memory exhaustion. Impact A misbehaving or malicious peer can cause a denial-of-service (DoS) attack against webtransport-go clients or servers by triggering excessive memory allocation, potentially leading to crashes or resource exhaustion. Details WebTransport sessions use capsules on the HTTP/3 request stream. Unknown capsule types are ignored, but the capsule body still needs to be consumed before the next capsule can be parsed. webtransport-go used io.ReadAll when skipping unknown capsules. Since the capsule reader is only limited by the capsule's declared length, a peer could send a large unknown capsule and cause the receiver to allocate memory for the full capsule body. QUIC flow…

Published by the source

18 Aug 2026, 14:32 UTC

Last modified by the source

18 Aug 2026, 15:00 UTC

Source last checked

26 Oct 2026, 15:27 UTC

1. Revision 2 · amended · 26 Oct 2026

   Amended from ghsa record GHSA-g35j-m5xg-vh3q

2. Revision 1 · created · 24 Oct 2026

   Published from osv record GO-2026-6099

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# Patch Next advisory brief: CVE-2026-57497

Advisory: webtransport-go: Memory Exhaustion Attack due to Buffering of Unknown Capsules
IDs: CVE-2026-57497, GHSA-g35j-m5xg-vh3q
Record: https://patchnext.com/advisories/cve-2026-57497 (revision 2, source checked 26 Oct 2026, 15:27 UTC)
Inventory: none attached. This brief comes from a public page and does not say whether any deployment is affected.
Severity: Medium (CVSS 5.3)
Exploitation: no confirmed exploitation recorded. Patch Next confirms exploitation only from CISA KEV.
Vendor response: Vendor fix available; fixed versions by package: github.com/quic-go/webtransport-go 0.11.1. A vendor fix does not mean a deployment is fixed.

## Affected components
- Go github.com/quic-go/webtransport-go: affected <= 0.11.0; fixed in 0.11.1

## Suggested inspection (read-only)
- Go github.com/quic-go/webtransport-go: check the installed version with your package manager.

## Supported action
Upgrade each affected component to a fixed version on its release line. For a transitive dependency, upgrade the parent package or add an override or constraint, then regenerate the lockfile. Redeploy every environment that ran an affected version.

## Required regression checks
- Run the test suite and a production build.
- Exercise the features that depend on github.com/quic-go/webtransport-go.
- Repeat the inspection and confirm that only fixed versions remain installed.

## Rollback considerations
- Keep the previous lockfile and deployment artifact. Rolling back reinstates the vulnerable version, so apply any documented mitigation while you fix forward.

## Unresolved questions
- Which deployments run an affected version?
- Exploitation status can change. Check again before lowering the priority.
- Mark the work resolved only after the fixed version is verified in production.

## Sources
- Verified: https://osv.dev/vulnerability/GO-2026-6099 (OSV record GO-2026-6099 lists affected ranges: Go github.com/quic-go/webtransport-go >=0 <0.11.1 (fixed))
- Verified: https://github.com/advisories/GHSA-g35j-m5xg-vh3q (GitHub-reviewed advisory GHSA-g35j-m5xg-vh3q lists affected ranges: Go github.com/quic-go/webtransport-go >=0 <=0.11.0)

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