CVE-2026-74757

Deferred Deferred - Pending Action

Memory Exhaustion in Apache bRPC via mcpack2pb

Publication date: 2026-10-21

Last updated on: 2026-10-26

Assigner: Apache Software Foundation

Description

Uncontrolled resource allocation in the mcpack2pb component in Apache bRPC (version < 1.18.0) on all platforms allows remote attackers to make the server allocate a large amount of memory via sending a crafted mcpack request with a huge array item count. Root Cause: The bRPC mcpack2pb parser trusts the item count stored in the mcpack array header without validating it against the actual payload size. The code generated by the mcpack2pb protoc plugin uses this count to preallocate memory for repeated protobuf fields via Reserve(). A malformed request declaring item_count = 0x7fffffff can force the server to preallocate about 16GB of virtual memory, which may abort the process (SIGABRT) on memory-constrained hosts. Affected Scenarios: Use a bRPC server that wires a NsheadService to UbrpcMcpack2Adaptor (the Baidu ubrpc deployment pattern) and parses requests with code generated by the mcpack2pb protoc plugin. The request body is parsed before authentication. How to Fix: (Choose one of the following options) 1. Upgrade bRPC to version 1.18.0, which fixes this issue. 2. Apply this patch: https://github.com/apache/brpc/pull/3451 Note: No matter which option you choose, you should know that the fix caps the array item count to the remaining bytes of the array payload.

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Meta Information

Published

2026-10-21

Last Modified

2026-10-26

Generated

2026-11-10

AI Q&A

2026-10-21

EPSS Evaluated

2026-11-09

NVD

CVE-2026-74757

EUVD

EUVD-2026-107181

Affected Vendors & Products

Vendor	Product	Version / Range
Apache Software Foundation	Apache bRPC	0

Helpful Resources

Exploitability

CWE

KEV

CWE ID	Description
CWE-770	The product allocates a reusable resource or group of resources on behalf of an actor without imposing any intended restrictions on the size or number of resources that can be allocated.

Attack-Flow Graph

Executive Summary

This vulnerability is an uncontrolled resource allocation issue in Apache bRPC's mcpack2pb component. It occurs when a remote attacker sends a crafted mcpack request with an extremely large array item count. The parser trusts this count without validating it against the actual payload size, leading to excessive memory preallocation (up to 16GB) during protobuf field processing.

Detection Guidance

Detecting this vulnerability requires monitoring for unusual memory allocation patterns in bRPC servers using mcpack2pb. Check for processes consuming excessive memory unexpectedly or logs showing malformed mcpack requests with large array item counts. Use system monitoring tools like top, htop, or ps to observe memory usage spikes in bRPC server processes.

Impact Analysis

This vulnerability can cause a bRPC server to crash due to memory exhaustion, especially on hosts with limited memory. The server may abort with a SIGABRT signal when attempting to allocate the excessive memory. It affects systems using the Baidu ubrpc deployment pattern with NsheadService and UbrpcMcpack2Adaptor.

Compliance Impact

This vulnerability could indirectly impact compliance with GDPR or HIPAA by enabling denial-of-service attacks that disrupt service availability. Memory exhaustion may cause system crashes, potentially leading to unauthorized data access or loss of critical services handling sensitive data.

Mitigation Strategies

Upgrade bRPC to version 1.18.0 or later to address the vulnerability directly.
If upgrading is not immediately possible, apply the patch from https://github.com/apache/brpc/pull/3451 to cap array item counts.
Monitor network traffic for malformed mcpack requests with suspiciously large array item counts as a temporary workaround.

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