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GHSA-g35j-m5xg-vh3q
No affected components available
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 control limits buffered data, but it does not bound total allocation here, since reading the stream advances the flow control window while retaining the received bytes in memory.
The Fix
webtransport-go now drains unknown capsules to io.Discard instead of buffering them. This consumes the capsule body so parsing can continue, without retaining the payload in memory.
The vulnerability can be exploited over the network without needing physical access. It is easy for an attacker to exploit this vulnerability. An attacker does not need any special privileges or access rights. No user interaction is needed for the attacker to exploit this vulnerability. The impact is confined to the system where the vulnerability exists. There is a low impact on the availability of the system.
Exploitation attempts have been detected. Elevated vigilance and prompt remediation are advised.
Probability that this vulnerability will be exploited in the wild within the next 30 days.
We did not find any exploit available. Neither in GitHub repositories nor in the Exploit-Database.
- CVE-2026-57497Alias
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