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CVE-2026-112021— snac2 before 2.93 Heap-Based Buffer Overflow via JSON Parser _xs_json_load_lexer()

Quick assessment

Affected
grunfink snac2
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.

在版本 2.93 之前的 snac2 中，_xs_json_load_lexer() 函数存在一个基于堆的缓冲区溢出漏洞。该漏洞允许未经身份验证的远程攻击者通过发送包含 \u0000 转义序列的 JSON 字符串，导致堆内存被破坏。攻击者可以向 activitypub_post_handler() 发送一个精心构造的 application/activity+json 格式 POST 请求；该请求在签名验证之前即被解析，从而引发堆内存分配溢出并导致服务器崩溃。

CVSS 7.5 · High

Possible ATT&CK Techniques 1 AI

T1190 · Exploit Public-Facing Application
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I. Basic Information for CVE-2026-112021

Vulnerability Information
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Vulnerability Title
snac2 before 2.93 Heap-Based Buffer Overflow via JSON Parser _xs_json_load_lexer()
Source: CVE Program / CVE List V5
Vulnerability Description
snac2 before 2.93 contains a heap-based buffer overflow vulnerability in _xs_json_load_lexer() that allows unauthenticated remote attackers to corrupt heap memory by sending JSON strings containing a \u0000 escape. Attackers can send a single crafted application/activity+json POST to activitypub_post_handler(), which parses it before signature checks, overflowing heap allocations and crashing the server.
Source: CVE Program / CVE List V5
CVSS Information
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
Source: CVE Program / CVE List V5
Vulnerability Type
堆缓冲区溢出
Source: CVE Program / CVE List V5

Affected Products

Vendor Product Affected Versions CPE Subscribe
grunfink snac2 0 ~ 2.93 -

II. Public POCs for CVE-2026-112021

# POC Description Source Link Shenlong Link
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III. Intelligence Information for CVE-2026-112021

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Vendor Advisories for CVE-2026-112021 (1)

Proof of Concept for CVE-2026-112021 (1)

Security Blog Posts for CVE-2026-112021 (1)

Other References for CVE-2026-112021 (4)

IV. Related Vulnerabilities

Same weakness: CWE-122

V. Comments for CVE-2026-112021

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