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.

Metrics

Attack Vector Network

Attack Complexity Low

Privileges Required None

Attack Requirements None

User Interaction None

Vulnerable System Confidentiality Impact None

Vulnerable System Integrity Impact None

Vulnerable System Availability Impact High

Subsequent System Confidentiality Impact None

Subsequent System Integrity Impact None

Subsequent System Availability Impact None

Attack Vector Network

Attack Complexity Low

Privileges Required None

Scope Unchanged

Confidentiality Impact None

Integrity Impact None

Availability Impact High

User Interaction None

No CVSS v3.0

No CVSS v2

This CVE is not in the KEV list.

No EPSS score available.

Key SSVC decision points have not yet been added.

Affected Vendors & Products

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Advisories

No advisories yet.

Fixes

Solution

No solution given by the vendor.

Workaround

No workaround given by the vendor.

References
Link Providers
https://codeberg.org/grunfink/snac2 cve-icon cve-icon
https://codeberg.org/grunfink/snac2/commit/ec2c5c2046e0381bc942ec5d0d05ec861fe377e7 cve-icon cve-icon
https://codeberg.org/grunfink/snac2/releases/tag/2.93 cve-icon cve-icon
https://codeberg.org/grunfink/snac2/src/tag/2.92/xs_json.h#L283-L285 cve-icon cve-icon
https://gist.github.com/nullenvk/2bf288e2d34cb3d4b7143e61dbf7d90b cve-icon cve-icon
https://nullenvk.pl/posts/02-snac2-json cve-icon cve-icon
https://www.vulncheck.com/advisories/snac2-before-2.93-heap-based-buffer-overflow-via-json-parser-xs-json-load-lexer cve-icon cve-icon
History

Sun, 18 Oct 2026 11:45:00 +0000

Type Values Removed Values Added
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.
Title snac2 before 2.93 Heap-Based Buffer Overflow via JSON Parser _xs_json_load_lexer()
Weaknesses CWE-122
References
Metrics cvssV3_1

{'score': 7.5, 'vector': 'CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H'}

cvssV4_0

{'score': 8.7, 'vector': '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'}

Projects

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cve-icon MITRE

Status: PUBLISHED

Assigner: VulnCheck

Published:

Updated: 2026-10-18T11:38:40.652Z

Reserved: 2026-10-18T01:24:56.329Z

Link: CVE-2026-112021

cve-icon Vulnrichment

No data.

cve-icon NVD

Status : Received

Published: 2026-10-18T12:17:15.200

Modified: 2026-10-18T12:17:15.200

Link: CVE-2026-112021

cve-icon Redhat

No data.

cve-icon OpenCVE Enrichment

Updated: 2026-10-18T12:45:01Z

Weaknesses