CVE-2026-112021
HIGH
CVSS 7.5
Published: 2026-10-18
Modified: 2026-10-19
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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.
Quick Facts
| CVE ID | CVE-2026-112021 |
| CVSS Score | 7.5 |
| Vector | CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H |
| Published | 2026-10-18 |
| Exploited | No |
| CISA KEV | No |
| PoC | Not public |
References
- https://codeberg.org/grunfink/snac2
- https://codeberg.org/grunfink/snac2/commit/ec2c5c2046e0381bc…
- https://codeberg.org/grunfink/snac2/releases/tag/2.93
- https://codeberg.org/grunfink/snac2/src/tag/2.92/xs_json.h#L…
- https://gist.github.com/nullenvk/2bf288e2d34cb3d4b7143e61dbf…
- https://nullenvk.pl/posts/02-snac2-json
- https://www.vulncheck.com/advisories/snac2-before-2.93-heap-…