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Vulnerabilities

Vulnerability · CVE-2026-21434

webtransport-go is an implementation of the WebTransport protocol.

Published Feb 12, 2026 · catalog updated Feb 12, 2026 · webtransport-go is an implementation

Last checked Nov 4, 2026. A connected source was read within the last 7 days.

Check if you run it

No confirmed exploitation is on record for CVE-2026-21434. EPSS is 0.46%. Act only if a listed version of webtransport-go is an implementation is installed.

Gaps on this record

  • The stored product name is a package slug. The name on this page is taken from the title (webtransport-go is an implementation).
  • No vendor fix or required action is stored. Compare the linked advisory before you change production.

Same product and reporting

Severity
Medium5.3
Known exploitation
Not in CISA/VulnCheck KEV
EPSS
0.46%
Remediation
Version ranges on file
Affected products
vendor quic-go webtransport-go < 0.10.0

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 mem

Are you affected?

Enter the version you run. The result uses only the ranges stored on this record.

The check returns affected, not affected, or incomplete. It does not guess a version that is missing from the record.

  • vendor quic-go webtransport-go < 0.10.0< 0.10.0

How to fix CVE-2026-21434

What to do

Three questions, each answered from this record only. Confirm the vendor advisory before you patch.

Should you patch?

No confirmed exploitation is on record for CVE-2026-21434. EPSS is 0.46%. Act only if a listed version of webtransport-go is an implementation is installed.

Which versions are affected?

Compare what you have installed with quic-go webtransport-go < 0.10.0 < 0.10.0. Compare the installed version with the linked vendor advisory before you change production.

What should an analyst verify?

No weakness class is stored. EPSS 0.46%. There is no CISA KEV listing. No Exploit-DB or Metasploit reference is linked. Use the source links for the original advisory.

Code

The project this record applies to. Exploit listings stay in References.

Timeline

Detection, updates, and resolution for this record.

  1. Feb 12, 2026 · EUVD

    Detected

    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 arb

  2. Feb 12, 2026 · EUVD

    Updated

    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 arb

Sources

  • CVE.orgVulnerability recordCVE-2026-21434

    Official CVE identifier

    cve.org
  • FIRST EPSSExploitation probabilityCVE-2026-21434

    30-day exploitation probability 0.46%

    first.org
  • EUVDVulnerability recordEUVD-2026-6715

    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.

    euvd.enisa.europa.eu

References

Freshness

Last verified in this catalog Nov 3, 2026. Significant claims (KEV, EPSS, CVSS, affected ranges) come from the source rows above — open the original publisher for the authoritative advisory.

  • CVE.orgNov 4, 2026
  • FIRST EPSSNov 3, 2026
  • EUVDNov 3, 2026