CVE-2026-112021
snac2 before 2.93 Heap-Based Buffer Overflow via JSON Parser _xs_json_load_lexer()
- State
- Published
- Severity
- 8.7 High
- Published
- Oct 18, 2026
- Updated
- Oct 19, 2026
- Reserved
- Oct 18, 2026
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.
Scores
| CVSS | Score | Vector | Source |
|---|---|---|---|
| 4.0 | 8.7 High | CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N | VulnCheck |
| 3.1 | 7.5 High | CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H | VulnCheck |
Weaknesses
- CWE-122 Heap-based Buffer Overflow
Affected Products
| Product | Versions |
|---|---|
snac2grunfink |
|
References
- https://nullenvk.pl/posts/02-snac2-jsontechnical-description
- https://gist.github.com/nullenvk/2bf288e2d34cb3d4b7143e61dbf7d90bexploit
- https://codeberg.org/grunfink/snac2/src/tag/2.92/xs_json.h#L283-L285technical-description
- https://codeberg.org/grunfink/snac2/commit/ec2c5c2046e0381bc942ec5d0d05ec861fe377e7patch
- https://codeberg.org/grunfink/snac2/releases/tag/2.93release-notes
- https://codeberg.org/grunfink/snac2product
- VulnCheck Advisory: snac2 before 2.93 Heap-Based Buffer Overflow via JSON Parser _xs_json_load_lexer()third-party-advisory
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