---
id: CVE-2026-112021
title: >-
  snac2 before 2.93 Heap-Based Buffer Overflow via JSON Parser
  _xs_json_load_lexer()
summary: >-
  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 s…
severity: high
cvss: 7.5
cvssVector: 'CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H'
cvssSource: cna
cwe:
  - CWE-122
vendor: grunfink
product: snac2
affected:
  - snac2 < 2.93
published: '2026-10-18'
updated: '2026-10-18'
sourceUpdated: '2026-10-18T11:38:40.652Z'
source: CVEORG
sourceUrl: 'https://www.cve.org/CVERecord?id=CVE-2026-112021'
references:
  - url: 'https://nullenvk.pl/posts/02-snac2-json'
  - url: 'https://gist.github.com/nullenvk/2bf288e2d34cb3d4b7143e61dbf7d90b'
  - url: 'https://codeberg.org/grunfink/snac2/src/tag/2.92/xs_json.h#L283-L285'
  - url: >-
      https://codeberg.org/grunfink/snac2/commit/ec2c5c2046e0381bc942ec5d0d05ec861fe377e7
  - url: 'https://codeberg.org/grunfink/snac2/releases/tag/2.93'
  - url: 'https://codeberg.org/grunfink/snac2'
  - url: >-
      https://www.vulncheck.com/advisories/snac2-before-2.93-heap-based-buffer-overflow-via-json-parser-xs-json-load-lexer
    label: >-
      VulnCheck Advisory: snac2 before 2.93 Heap-Based Buffer Overflow via JSON
      Parser _xs_json_load_lexer()
tags:
  - cve.org
ingestedAt: '2026-10-18T11:40:26.618Z'
---

## Overview

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.

## Affected

- `snac2 < 2.93`

## Remediation

Refer to the linked advisories for vendor-supplied fixes and affected version ranges.