CVE-2026-78663NVD

Vulnerability Summary

The HTTP/2 server can refund connection-level flow control twice for the same data: Once when a client resets a stream (refunding data for any sent-but-unread portion of the stream), and again when a request handler reads the buffered data. A malicious client can exploit this to bypass the configured connection-level flow control limit (MaxReceiveBufferPerConnection). Total buffered data is still limited by the concurrent stream limit and stream-level flow control.

Severity Level

CRITICAL(9.1)

Published Date

Oct 8, 2026

Last Modified

Oct 9, 2026

Exploitation Status

No confirmed exploitation yet

EPSS Score (30-Day)

0.25%Probability

Root Weakness (CWE)

CWE-675: Unknown/Unlisted Weakness ↗

Refer to the official MITRE database for detailed architectural specifications regarding this weakness.

CVSS v3.1 Base Metrics — Score 9.1 (CRITICAL)

Attack VectorNetwork

Attack ComplexityLow

Privileges RequiredNone

User InteractionNone

ScopeUnchanged

ConfidentialityNone

IntegrityHigh

AvailabilityHigh

Affected & Patched Versions

Affected Versions

Not provided by NVD for this CVE.

Patched Versions

Not provided by NVD for this CVE.

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