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.
Affected products
| Vendor | Product | Affected | Fixed |
|---|---|---|---|
| grunfink | snac2 | < 2.93 | 2.93 |
Fixed in Linux distributions
Distributions backport fixes, so the version that fixes this vulnerability differs per release — upgrade to at least the version shown. From the distributions' security trackers and advisories.
Debian
Security tracker ↗| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| Debian 14 | snac2 | 2.93-1 | — |
| Debian 13 | snac2 | No fix yet | — |
Ubuntu
Security tracker ↗| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| Ubuntu 26.04 LTS | snac2 | No fix yet | — |
| Ubuntu 24.04 LTS | snac2 | No fix yet | — |
References
- https://nullenvk.pl/posts/02-snac2-json technical-description
- https://gist.github.com/nullenvk/2bf288e2d34cb3d4b7143e61dbf7d90b exploit
- https://codeberg.org/grunfink/snac2/src/tag/2.92/xs_json.h#L283-L285 technical-description
- https://codeberg.org/grunfink/snac2/commit/ec2c5c2046e0381bc942ec5d0d05ec861fe377e7 patch
- https://codeberg.org/grunfink/snac2/releases/tag/2.93 release-notes
- https://codeberg.org/grunfink/snac2 product
- VulnCheck Advisory: snac2 before 2.93 Heap-Based Buffer Overflow via JSON Parser _xs_json_load_lexer() third-party-advisory