CVE-2026-112021snac2 before 2.93 Heap-Based Buffer Overflow via JSON Parser _xs_json_load_lexer()
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No exploitation reported and no EPSS estimate yet.
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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.
- CVSS
- 7.5 HIGH (v3.1, CNA)CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
- Weakness (CWE)
- CWE-122
- Known exploited
- Not in CISA's KEV catalog
- EPSS (exploitation in the next 30 days)
- Not loaded for this CVE
- Assigned by
- VulnCheck
- NVD analysis
- Received
- Record last updated
- Oct 18, 2026
- First seen by InfoSec Signals
- Oct 18, 2026
Affected products
grunfink snac2 grunfink:snac2 (from the name) | before 2.93 | CNA record |
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
- https://www.vulncheck.com/advisories/snac2-before-2.93-heap-based-buffer-overflow-via-json-parser-xs-json-load-lexerthird-party-advisory
The CVE record on cve.org NVD's entry
The CVE record is authoritative. Products marked “from the name” were identified from the CNA's free-text names, not a CPE, and are matched less certainly. This product uses the NVD API but is not endorsed or certified by the NVD.