CVE-2026-21434
MEDIUM
GHSA-g6x7-jq8p-6q9q
CVSS Vector
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L
Lifecycle Timeline
3Tags
Description
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 memory consumption, but the lack of any upper bound makes large-scale attacks feasible given sufficient bandwidth. This vulnerability is fixed in 0.10.0.
Analysis
Webtransport-go versions 0.3.0 through 0.9.0 fail to enforce the 1024-byte limit on Application Error Messages in WT_CLOSE_SESSION capsules, allowing remote attackers to trigger unbounded memory consumption by sending oversized payloads. An unauthenticated attacker can exhaust server memory and cause denial of service, requiring only sufficient bandwidth to transmit the malicious payload. …
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Remediation
Within 30 days: Identify affected systems and apply vendor patches as part of regular patch cycle. Monitor vendor channels for patch availability.
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