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CVE-2026-74755— Apache bRPC: Integer Underflow in mcpack2pb Parser Leading to Denial of Service

Quick assessment

Affected
Apache Software Foundation Apache bRPC
Exploitation
No confirmed in-the-wild exploitation; assess based on exposure
Recommended action
Check the vendor advisory and references for a fixed version. If immediate upgrade is impossible, restrict exposure and increase monitoring.

在 Apache bRPC（版本 < 1.18.0）的 mcpack2pb 组件中存在一个整数下溢漏洞，该漏洞存在于所有平台上。远程攻击者可通过发送包含 为零的字符串字段的请求，导致 bRPC 服务器崩溃。具体而言， 函数在计算 时未对 进行有效性校验；当 为 0 时，该表达式会发生下溢，结果为 。随后调用的 函数会抛出 异常。由于该异常在请求解析路径中未被捕获，最终导致进程终止（触发 SIGABRT 信号）。 根本原因： 在 中， 函数将输出字符串的大小调整为 ，其中 直接取自网络数据中的字符串字段的 。当 为

AI Predicted 7.5 Difficulty: Easy

Possible ATT&CK Techniques 1 AI

T1190 · Exploit Public-Facing Application

Affected Version Matrix 1

VendorProduct Version RangeStatus
Apache Software Foundation Apache bRPC < 1.18.0 affected
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I. Basic Information for CVE-2026-74755

Vulnerability Information
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Vulnerability Title
Apache bRPC: Integer Underflow in mcpack2pb Parser Leading to Denial of Service
Source: CVE Program / CVE List V5
Vulnerability Description
An integer underflow in the mcpack2pb component of Apache bRPC (version < 1.18.0) on all platforms allows remote attackers to crash a bRPC server by sending a request containing a string field with a zero value_size. The UnparsedValue::as_string() function computes `_size - 1` without validating `_size`; when value_size is 0 the expression underflows to SIZE_MAX, resize() throws std::length_error, and because the exception is not caught on the request parsing path the process aborts (SIGABRT). Root Cause: In src/mcpack2pb/parser.cpp, UnparsedValue::as_string() resizes the output string to `_size - 1`, where `_size` is the value_size of a string field taken directly from the network data. A value_size of 0 underflows the unsigned size_t, and the subsequent resize() throws an exception that is not caught. Affected Scenarios: bRPC servers that accept nshead frames wired to the ubrpc mcpack2 adaptor (for example the NsheadService + UbrpcMcpack2Adaptor deployment pattern) can be crashed by a single unauthenticated request. Stock open-source bRPC registers the ubrpc/nshead_mcpack protocols as client-only, so default server configurations are not affected. How to Fix: 1. Upgrade bRPC to a version that includes this fix. 2. Apply the patch in PR  https://github.com/apache/brpc/pull/3450
Source: CVE Program / CVE List V5
CVSS Information
N/A
Source: CVE Program / CVE List V5
Vulnerability Type
整数下溢(超界折返)
Source: CVE Program / CVE List V5

Affected Products

Vendor Product Affected Versions CPE Subscribe
Apache Software Foundation Apache bRPC 0 ~ 1.18.0 -

II. Public POCs for CVE-2026-74755

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III. Intelligence Information for CVE-2026-74755

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Same Patch Batch · Apache Software Foundation · 2026-10-21 · 69 CVEs total

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CVE-2026-111804 8.2 HIGH Apache Traffic Server: wasm plugin has a use-after-free and forwards unvalidated guest met
CVE-2026-105945 7.7 HIGH Apache Pulsar: Improper Validation of Package Name Components Allows Cross-Tenant Package
CVE-2026-105942 7.7 HIGH Apache Pulsar: Original principal of proxied requests authorized with the proxy's authenti
CVE-2026-111810 7.5 HIGH Apache Traffic Server: Unthrottled per-header diagnostic logging enables a log-flood denia
CVE-2026-105934 7.2 HIGH Apache Pulsar: Missing tenant admin authorization check when truncating a partitioned topi
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Showing top 20 of 69 CVEs. View all on vendor page &rarr; →

IV. Related Vulnerabilities

Same product: Apache bRPC
Same vendor: Apache Software Foundation
Same weakness: CWE-191

V. Comments for CVE-2026-74755

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