CVE-2026-112021CWE-122

CVE-2026-112021

High · published October 18, 2026

CVSS v3.1
7.5
EPSS
1%
Percentile
51.5
In the wild
Unconfirmed
What it is

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.

The record
Technical detail
CVSS v3.1
7.5 · HIGH
Vector
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
CVSS v4.0
8.7 · 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
EPSS
0.00670 · 51.5th percentile
Weakness
CWE-122 · Heap-based Buffer Overflow
Published
2026-10-18T16:17Z
References (7)
https://codeberg.org/grunfink/snac2 · [email protected]https://codeberg.org/grunfink/snac2/commit/ec2c5c2046e0381bc942ec5d0d05ec861fe377e7 · [email protected]https://codeberg.org/grunfink/snac2/releases/tag/2.93 · [email protected]https://codeberg.org/grunfink/snac2/src/tag/2.92/xs_json.h#L283-L285 · [email protected]https://gist.github.com/nullenvk/2bf288e2d34cb3d4b7143e61dbf7d90b · [email protected]https://nullenvk.pl/posts/02-snac2-json · [email protected]https://www.vulncheck.com/advisories/snac2-before-2.93-heap-based-buffer-overflow-via-json-parser-xs-json-load-lexer · [email protected]
EPSS history
Timeline
  • 20 OCT 03:29Z
    EPSS moved — → 1%
    epss
  • 18 OCT 11:38Z
    snac2 before 2.93 Heap-Based Buffer Overflow via JSON Parser _xs_json_load_lexer()
    cvelistv5
  • 18 OCT 11:38Z
    snac2 before 2.93 Heap-Based Buffer Overflow via JSON Parser _xs_json_load_lexer()
    cvelistv5