Unscored severity · published Oct 21, 2026
CVE-2026-56387
Apache bRPC: Remote Memory Exhaustion in RTMP AMF Parser
New
–
CVSS
0.3%
EPSS
No
On KEV
Description
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:
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.
Exploitation
Is it being used?
Exploit prediction (EPSS)0.3% · higher than 20% of CVEs
Exploited in the wildNo evidence yet
CISA KEVNot listed
Ransomware campaign useNot known
Affected products
Which versions
AB
Apache bRPC · Apache Software Foundation
before 1.18.0 · source: vendor
References
NVD
https://nvd.nist.gov/vuln/detail/CVE-2026-56387
CVE.org
https://www.cve.org/CVERecord?id=CVE-2026-56387
lists.apache.org
https://lists.apache.org/thread/2pf15ojj0vr7rtx95677kgtl1mx3gdgb
More from Apache bRPC
7.5
CVE-2026-82230
Apache bRPC: Stack Exhaustion via Unbounded Recursion in mcpack2pb Parser
7.5
CVE-2026-74757
Apache bRPC: Uncontrolled Memory Allocation via Malicious mcpack Array Item Count
7.5
CVE-2026-56386
Apache bRPC: Integer Underflow and Out-of-Bounds Read in HTTP/2 DATA Frame Parser
6.5
CVE-2026-90484
Apache bRPC: Null pointer dereference in MySQL reply parser leading to client crash
5.4
CVE-2026-84727
Apache bRPC: Use-After-Free in RTMP Chunk Stream Handling via Abort Message
