CVE-2026-21434Network attack vector

Memory exhaustion via unbounded close-message read

Published Feb 12, 2026 · Updated Feb 12, 2026

Resource exhaustion in quic-go webtransport-go 0.3.0 through 0.9.0 allows remote attackers to consume memory via a close capsule. The session parser fully reads and stores a WT_CLOSE_SESSION Application Error Message without enforcing its 1,024-byte protocol limit. Exploitation requires transmission of the entire payload; memory consumption then scales with attacker-supplied data and pressures the process or host.

CVSS severity7.5
High
EPSS probability0.43%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Resource exhaustion in quic-go webtransport-go 0.3.0 through 0.9.0 allows remote attackers to consume memory via a close capsule. The session parser fully reads and stores a WT_CLOSE_SESSION Application Error Message without enforcing its 1,024-byte protocol limit. Exploitation requires transmission of the entire payload; memory consumption then scales with attacker-supplied data and pressures the process or host.

The record

CVE
CVE-2026-21434
Published
Feb 12, 2026
Updated
Feb 12, 2026
Vendor
quic-go
Product
webtransport-go
Classifications
CWE-770, T1499.003
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Feb 12, 2026CVE publishedPublication date reported by the CVE source.
  2. Feb 12, 2026Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

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Is a vulnerable build present?

Compare these published version ranges with your installed build and any vendor patches.

  1. Affected versionversion=< 0.10.0

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

quic-go · webtransport-goversion=< 0.10.0

Published CVSS scores

7.5NIST NVDCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
5.3GitHub, Inc.CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

Daily unique IPsNo honeypot observations are available for this CVE in the selected window.

No observations available

Sep 10, 2026Sep 16, 2026
Latest reporting daySep 16, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-770Allocation of Resources Without Limits or Throttling
T1499.003Application Exhaustion Flood

Public exploit references

No public exploit references are available in this record.

Labels summarize the accepted research assessment. They do not indicate a test against your environment.

Technologies

Your stack

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Your stack

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