{"id":"CVE-2026-78048","title":"Apache bRPC: Remote Denial of Service via Out-of-Bounds Dynamic Table Sizing in HPACK Decoder","summary":"A reachable-assertion flaw in the HPACK header-compression decoder of the HTTP/2 (h2/gRPC) stack in Apache bRPC (version < 1.18.0) on all platforms allows a remote attacker to crash the server process by sending a crafted sequence of HPA…","severity":"none","cwe":["CWE-617"],"vendor":"Apache Software Foundation","product":"apache/brpc","affected":["apache/brpc < 1.18.0"],"published":"2026-10-21","updated":"2026-10-21","sourceUpdated":"2026-10-21T11:51:58.752Z","source":"CVEORG","sourceUrl":"https://www.cve.org/CVERecord?id=CVE-2026-78048","references":[{"url":"https://lists.apache.org/thread/2pf15ojj0vr7rtx95677kgtl1mx3gdgb"}],"tags":["cve.org"],"ingestedAt":"2026-10-21T12:48:53.763Z","slug":"CVE-2026-78048","body":"## Overview\n\nA reachable-assertion flaw in the HPACK header-compression decoder of the HTTP/2 (h2/gRPC) stack in Apache bRPC (version < 1.18.0) on all platforms allows a remote attacker to crash the server process by sending a crafted sequence of HPACK headers, resulting in a denial of service.\n\nRoot Cause:\nIn src/brpc/details/hpack.cpp, IndexTable::Init sizes the dynamic-table ring buffer as num_headers = max_size / (32 + 2), i.e. it assumes a minimum table entry of 34 bytes (name >= 1 byte + value >= 1 byte + 32 bytes of overhead). However, RFC 7541 section 4.1 specifies that the minimum entry size is 33 bytes, because the value may be empty (name >= 1 byte + value == 0 + 32 bytes). For the default 4096-byte table this allocates only 120 slots (4096/34). Eviction in AddHeader is driven by byte usage (_max_size), not by slot count, so a peer can add 121 minimal 33-byte entries (121*33 = 3993 <= 4096) without triggering eviction. The 121st AddHeader then hits CHECK(!_header_queue.full()), which aborts the process.\n\nAffected Scenarios:\nUse a bRPC server that serves HTTP/2 or gRPC requests (e.g. via the h2 protocol) from an untrusted network. The malicious header block is processed during HPACK decoding of incoming requests without authentication.\n\nHow to Fix: \n(Choose one of the following options) \n1. Upgrade bRPC to version 1.18.0, which fixes this issue.\n2. Apply this patch: https://github.com/apache/brpc/pull/3462\n\nNote:\nThe fix sizes the dynamic table for the 33-byte minimum entry (max_size / (32 + 1)) and ensures at least one ring-buffer slot is kept when max_size is smaller than the minimum entry, so that initialization cannot fail on malloc(0).\n\n## Affected\n\n- `apache/brpc < 1.18.0`\n\n## Remediation\n\nRefer to the linked advisories for vendor-supplied fixes and affected version ranges.","depth":"sunlit","depthScore":3,"depthScoreParts":{"impact":2.8,"likelihood":0,"exploitation":0,"ransomware":0},"changes":[]}