CVE-2026-56386

Affected and fixed versions

Neither OSV.dev nor the vendor advisories we read list affected versions for CVE-2026-56386 yet.

Full record on NVD

Description

Integer underflow and out-of-bounds read in the HTTP/2 server DATA frame parser in Apache bRPC allows an unauthenticated remote attacker to cause denial of service by sending a malformed DATA frame with the PADDED flag set and a zero-length payload. Root Cause: The HTTP/2 DATA frame handler computed the fragment size from the attacker-controlled payload length and, when the PADDED flag was present, decremented the fragment size before ensuring that the frame contained the mandatory pad length byte. A zero-length padded DATA frame could therefore underflow the unsigned fragment size and read the pad length byte past the end of the frame buffer. Affected Scenarios: Apache bRPC servers that accept HTTP/2 traffic are affected when a remote client can send crafted HTTP/2 frames to the server. HTTP/2 may be reached through cleartext h2c detection on an HTTP port or through TLS ALPN negotiation. How to Fix: (Choose one of the following options) 1. Upgrade Apache bRPC to version 1.18.0, which fixes this issue. 2. Apply this patch: https://github.com/apache/brpc/pull/3325 Note: The fix validates that a padded DATA frame has enough payload bytes for the pad length field before decrementing the fragment size or reading the pad length byte. Malformed zero-length padded DATA frames are rejected with HTTP/2 FRAME_SIZE_ERROR.

Technical details

CVSS v3 Vector

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

Published

2026-10-21

Last Modified

2026-10-22

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