Live › vulnerability › CVE-2026-56387
Go to dashboardThe RTMP AMF parser in Apache bRPC trusts string lengths and array counts declared in incoming data before checking the payload holds that many bytes. A remote unauthenticated attacker can send a small payload that forces excessive memory allocation or resource use, causing denial of service.
Summary written from the sources below. Check the originals before acting.
First seen by InfraStack 2026-10-23 21:57 UTC. All times on this page are UTC.
Deployments that enable the bRPC RTMP server component and accept RTMP connections from untrusted clients are exposed. Direct uses of the AMF parser on untrusted input are also affected. Servers that do not enable RTMP, or only accept trusted input, can skip it.
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grep -r 'BRPC_VERSION\|brpc' CMakeLists.txt or your package manager, and compare it with 1.18.0.1.18.0.amf_max_string_size (default 64 MiB) and amf_max_array_size (default 1,048,576) if the defaults do not fit your workload.Each row is the first time that source carried this signal. The analyst’s rows are its own findings.
The RTMP AMF parser in Apache bRPC accepts AMF string lengths and array counts directly from untrusted input. A remote unauthenticated attacker who can reach a bRPC server with RTMP enabled can send a small AMF payload with an excessive declared long string length or array count, causing excessive memory allocation or resource consumption before the parser rejects the incomplete payload.
Root Cause: The AMF long string parser resized the destination string to the declared 32-bit length before validating that the stream contained that many bytes. ECMA array and strict array parsers also accepted 32-bit element counts without a configurable upper bound.
Affected Scenarios: Deployments that enable the bRPC RTMP server component and accept RTMP traffic from untrusted clients. Direct uses of the AMF parser on untrusted data are also affected.
How to Fix:
Note: The fix introduces configurable AMF parsing limits. The default maximum string size is 64 MiB and the default maximum array element count is 1,048,576. Payloads above these limits are rejected. The limits can be adjusted with amf_max_string_size and amf_max_array_size.
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