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TI-2026-76173 Aliases CVE-2026-112021GHSA-6hv3-2r7g-774j

Heap overflow in snac2 JSON parser lets remote attackers crash server

Priority HIGH 77CWE-122Published · Updated

Key facts

Attack vector
Network
Privileges required
None
User interaction
None
Attack complexity
Low
Attack requirements
None
Impact type
Denial of service
Confidentiality · integrity · availability
None · None · High
Fix status
Fixed

Attack profile from CVSS 4.0 · CNA. Fix status from CNA. Impact type from CWE-122 and the CVSS impact.

Summary

snac2 from 0 before 2.93 contains a heap-based buffer overflow in _xs_json_load_lexer() (CWE-122). A JSON string containing a \u0000 escape corrupts heap memory, so an unauthenticated remote attacker can crash the server by sending a single crafted application/activity+json POST to activitypub_post_handler(), which parses it before signature checks. A public exploit is linked in the references.

Written with Claude Haiku 5.5 from the sources below · 2026-10-28

Description from the CNA

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.

Why it matters now

Exploitation Proof of concept CISA SSVC · not in CISA KEV
EPSS 0.0067 52nd percentileScored 2026-11-07
Public exploit Yes 1 exploit referenceTagged by the CNA
Fix Fixed snac2 (grunfink): 2.93

SSVC decision points

CISA ADP · SSVC 2.0.3

Exploitation
Poc
Automatable
Yes
Technical impact
Partial

The decision (Track, Attend, Act) also depends on your mission and well-being impact; see CISA's SSVC guide.

Affected products

VendorProductAffected versionsFixed inStatusSource
grunfinksnac2before 2.932.93Patch availableCNA
  • snac2 Vendorgrunfink Affected before 2.93 Fixed in 2.93 Patch available CNA

Remediation

Upgrade snac2 to version 2.93. The sources list no fix for other versions. CISA SSVC data lists exploitation as proof of concept, not as known exploited.

Written with Claude Haiku 5.5 from the sources below · 2026-10-28

  • Fix · CNA snac2 (grunfink) Fixed in 2.93

Timeline

  1. 2026-10-18 Threatist record created from CVE-2026-112021
  2. 2026-10-18 Alias added: GHSA-6hv3-2r7g-774j
  3. 2026-10-19 CISA SSVC decision points changed
  4. 2026-10-19 Priority changed: MEDIUM → HIGH

References

Exploit 1

Patch 1

Other 4

Sources

This product uses the NVD API but is not endorsed or certified by the NVD. Sources and licences