CVE-2026-112021

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.

References

• https://codeberg.org/grunfink/snac2
• https://codeberg.org/grunfink/snac2/commit/ec2c5c2046e0381bc942ec5d0d05ec861fe377e7
• https://codeberg.org/grunfink/snac2/releases/tag/2.93
• https://codeberg.org/grunfink/snac2/src/tag/2.92/xs_json.h#L283-L285
• https://gist.github.com/nullenvk/2bf288e2d34cb3d4b7143e61dbf7d90b