{"id":"CVE-2026-78048","kind":"vulnerability","aliases":["CVE-2026-78048"],"related":[],"title":"Apache bRPC: crafted HPACK headers crash HTTP/2 and gRPC servers","description":"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 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).","summary":"A remote client can send a crafted sequence of HPACK-compressed HTTP/2 headers to a bRPC server, tripping an assertion that aborts the whole process. The result is a denial of service with no authentication needed.","severity":"high","cvss":null,"epss":0.00242,"exploited":false,"exploited_at":null,"products":[],"ecosystems":[],"tags":["bpc","c++","grpc","http2","package","self-hosted"],"not_affected_if":["http1-only","internal-network-only","not-using-brpc"],"how_to_check":"- Run `grep -rn \"brpc\" CMakeLists.txt` or check your lock files and build manifests for the bRPC version in use\n- Check that the bRPC library version is below `1.18.0` on any server that accepts HTTP/2 or gRPC traffic from untrusted networks","fix":"- Upgrade Apache bRPC to `1.18.0` or later\n- Alternatively, apply the patch from https://github.com/apache/brpc/pull/3462","status":"open","published_at":"2026-10-21T12:17:23+00:00","first_seen_at":"2026-10-23T21:57:28+00:00","triaged_at":"2026-10-25T05:02:39+00:00","updated_at":"2026-10-25T05:02:39+00:00","category":"package","confidence":0.8,"triage":{"at":"2026-10-25T05:02:39Z","model":"claude-haiku-5-5","output":{"fix":"- Upgrade Apache bRPC to `1.18.0` or later\n- Alternatively, apply the patch from https://github.com/apache/brpc/pull/3462","reach":"internet","title":"Apache bRPC: crafted HPACK headers crash HTTP/2 and gRPC servers","impact":"low","summary":"A remote client can send a crafted sequence of HPACK-compressed HTTP/2 headers to a bRPC server, tripping an assertion that aborts the whole process. The result is a denial of service with no authentication needed.","category":"package","nicknames":[],"who_cares":["bpc","grpc","http2","c++","self-hosted"],"confidence":0.8,"needs_auth":"no","worst_case":"Remote client crashes the bRPC server process, causing denial of service.","analyst_note":"","how_to_check":"- Run `grep -rn \"brpc\" CMakeLists.txt` or check your lock files and build manifests for the bRPC version in use\n- Check that the bRPC library version is below `1.18.0` on any server that accepts HTTP/2 or gRPC traffic from untrusted networks","needs_analyst":false,"not_affected_if":["http1-only","internal-network-only","not-using-brpc"],"who_is_affected":"Any bRPC server that accepts HTTP/2 or gRPC requests from an untrusted network is exposed, because HPACK header decoding runs on every incoming request before any authentication. Servers that only speak HTTP/1.x, or that are reachable only from trusted internal networks, are less exposed. Teams not running bRPC can skip it.","user_interaction":"no","needs_special_setup":"no","severity_if_unknown":"high"},"cost_usd":0.000687,"input_tokens":3944,"output_tokens":585,"severity_before":"unknown"},"analyst_status":null,"analyst_note":null,"search":"'-2026':12A,15A '-78048':13A,16A '/apache/brpc/pull/3462':291C '0':174C,336C '1':141C,144C,171C,275C,308C '1.18.0':83C,280C '120':186C '121':208C,213C '121st':221C '2':129C,285C '32':128C,146C,175C,307C '33':162C,210C,214C,301C '34':138C '3993':215C '4.1':154C '4096':180C,216C '4096/34':188C '7541':152C 'abort':47B,228C 'add':207C 'addhead':191C,222C 'affect':231C 'alloc':184C 'allow':87C 'apach':1A,80C 'appli':286C 'assert':45B,65C 'assum':132C 'attack':90C 'authent':60B,265C 'block':255C 'bpc':17B 'brpc':2A,41B,81C,235C,277C 'buffer':122C,316C 'byte':139C,142C,145C,147C,163C,172C,176C,181C,195C,211C,302C 'c':18B 'cannot':332C 'caus':111C 'check':225C 'choos':269C 'client':27B 'compress':36B,72C 'count':202C 'craft':3A,31B,99C 'crash':6A,92C 'cve':11A,14A 'decod':73C,260C 'default':179C 'denial':55B,107C 'driven':193C 'dynam':119C,297C 'dynamic-t':118C 'e.g':243C 'empti':169C 'ensur':310C 'entri':136C,159C,212C,304C,328C 'evict':189C,219C 'fail':333C 'fix':268C,282C,294C 'flaw':66C 'follow':273C 'github.com':290C 'github.com/apache/brpc/pull/3462':289C 'grpc':9A,19B,241C 'h2':246C 'h2/grpc':77C 'header':5A,38B,71C,103C,125C,254C 'header-compress':70C 'header_queue.full':226C 'hit':224C 'host':24B 'howev':150C 'hpack':4A,35B,69C,102C,259C 'hpack-compress':34B 'http/2':7A,37B,76C,239C 'http2':20B 'i.e':130C 'incom':262C 'indext':114C 'init':115C 'initi':331C 'issu':284C 'kept':319C 'least':312C 'malici':253C 'malloc':335C 'max':126C,197C,305C,321C 'may':167C 'minim':209C 'minimum':134C,158C,303C,327C 'name':140C,170C 'need':61B 'network':251C 'note':292C 'num':124C 'one':270C,313C 'option':274C 'overhead':149C 'packag':21B 'patch':288C 'peer':205C 'platform':86C 'process':50B,95C,230C,257C 'protocol':247C 'reachabl':64C 'reachable-assert':63C 'remot':26B,89C 'request':242C,263C 'result':52B,104C 'rfc':151C 'ring':121C,315C 'ring-buff':314C 'root':110C 'scenario':232C 'section':153C 'self':23B 'self-host':22B 'send':29B,97C 'sequenc':32B,100C 'serv':238C 'server':10A,42B,94C,236C 'servic':57B,109C 'size':116C,127C,160C,198C,295C,306C,322C 'slot':187C,201C,317C 'smaller':324C 'specifi':155C 'src/brpc/details/hpack.cpp':113C 'stack':78C 'tabl':120C,135C,182C,298C 'trigger':218C 'trip':43B 'untrust':250C 'upgrad':276C 'usag':196C 'use':233C 'valu':143C,166C,173C 'version':82C,279C 'via':244C 'whole':49B 'without':217C,264C","nicknames":[],"mitigations":[],"who_affected":"Any bRPC server that accepts HTTP/2 or gRPC requests from an untrusted network is exposed, because HPACK header decoding runs on every incoming request before any authentication. Servers that only speak HTTP/1.x, or that are reachable only from trusted internal networks, are less exposed. Teams not running bRPC can skip it.","tier":"B","verified":{},"analyst_revisit_at":null,"first_public_at":"2026-10-21T12:17:23+00:00","kev":null,"cvss_vector":null,"cvss_by":null,"poc_count":0,"sources":[{"source":"nvd","external_id":"CVE-2026-78048","url":"https://nvd.nist.gov/vuln/detail/CVE-2026-78048","severity":null,"published_at":"2026-10-21T12:17:23+00:00","modified_at":"2026-10-22T16:56:37+00:00","first_seen_at":"2026-10-23T21:57:28+00:00","fetched_at":"2026-10-23T22:29:01+00:00","note":null},{"source":"epss","external_id":"CVE-2026-78048","url":"https://api.first.org/data/v1/epss?cve=CVE-2026-78048","severity":null,"published_at":null,"modified_at":null,"first_seen_at":"2026-10-24T13:15:54+00:00","fetched_at":"2026-10-24T13:15:54+00:00","note":null}],"documents":[],"notice":"Free to read at a human pace. An API with keys and an MCP server are in preparation; early access: hello@infrastack.ai"}