CVE-2026-112021
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.
Does this matter?
High impact if exploited, but EPSS currently rates exploitation as unlikely (0.67%). Schedule it in the normal patch cycle and watch for a rise in EPSS or a public exploit.
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.
- CVSS 4.0
- 8.7 HIGHCVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/M
- EPSS
- 0.67% probability · 52th percentile
- Public exploits
- None in Exploit-DB
- CISA KEV
- Not listed
- Weakness
- CWE-122
- Source
- disclosure@vulncheck.com
EPSS moved from 0.7% on 19 October 2026 to 0.7% on 27 October 2026.
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
- https://nullenvk.pl/posts/02-snac2-json
- https://www.vulncheck.com/advisories/snac2-before-2.93-heap-based-buffer-overflow-via-json-parser-xs-json-load-lexer
Source: NVD record, EPSS from FIRST.org, KEV from CISA, exploits from Exploit-DB. Refreshed daily. Download this record as JSON.