Apache bRPC: Remote Memory Exhaustion in RTMP AMF Parser

MITRE NVD CVE.ORG JSON API

Summary

CVECVE-2026-56387
StatePUBLISHED
Assignerapache
Source PriorityCVE Program / NVD first with legacy fallback
Published2026-10-21 12:17:21 UTC
Updated2026-10-22 16:56:37 UTC
DescriptionThe 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: 1. Upgrade bRPC to version 1.18.0, which fixes this issue. 2. Apply this patch:  https://github.com/apache/brpc/pull/3353 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.

Risk And Classification

EPSS: 0.002740000 probability, percentile 0.187190000 (date 2026-10-22)

Problem Types: CWE-770 | CWE-789 | CWE-789 CWE-789 Memory Allocation with Excessive Size Value | CWE-770 CWE-770 Allocation of Resources Without Limits or Throttling

Vendor Declared Affected Products

SourceVendorProductVersionPlatforms
CNA Apache Software Foundation Apache BRPC affected 1.18.0 semver Not specified

References

ReferenceSourceLinkTags
lists.apache.org/thread/2pf15ojj0vr7rtx95677kgtl1mx3gdgb [email protected] lists.apache.org
CVE Program record CVE.ORG www.cve.org canonical
NVD vulnerability detail NVD nvd.nist.gov canonical, analysis

Vendor Comments And Credit

Discovery Credit

CNA: Nikko Enggaliano Pratama (en)

CNA: 73Lab of Qingteng.cn (en)

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