# flatcc through 0.6.4 Out-of-Bounds Read via \_\_flatcc_json_parser_number

CVE record · `CVE-2026-116733`

- **Identifiers:** `CVE-2026-116733`
- **State:** Confirmed
- **Severity:** CVSS 6.3 Medium
- **Critical:** No
- **CNA:** VulnCheck
- **Weakness (CWE):** [CWE-125](https://cwe.mitre.org/data/definitions/125.html)
- **Tags:** [Memory corruption](https://agentprime.io/advisories/tag/memory-corruption.md)
- **Technologies:** [dvidelabs flatcc](https://agentprime.io/advisories/technology/dvidelabs-flatcc.md)
- **Published:** 26 Oct 2026
- **Updated:** 2 Nov 2026
- **Reviewed by a person:** No

Published by the CVE Program (CNA: VulnCheck) at 26 Oct 2026, 21:52 UTC. agentprime has not analysed this yet, so whether it affects any app is not known. This CVE names a vendor and product rather than a package, so the lockfile check doesn’t match it.

## Affected products, as the CNA wrote them

- Vendor: dvidelabs. Product: flatcc.
  - affected: `0.6.4 and earlier` (custom)
  - Other versions: unaffected
  - purl: `pkg:github/dvidelabs/flatcc`

## Machine-written summary

Summary written by Claude Haiku from the source advisory. Not reviewed by a person.

> flatcc versions through 0.6.4 contain an out-of-bounds read in the \_\_flatcc_json_parser_number function. An attacker who can supply untrusted JSON to a generated parser can send a number ending directly after a decimal point, causing the parser to read past the input buffer and potentially crash the application. The source gives no fixed version or workaround.

Written 14 Nov 2026.

## Not analysed yet

We haven’t published our own analysis of this CVE. If a person reviews it, this page will say what’s affected and what has to be true for it to matter.

## Severity and exploitation

- 6.3 Medium, CVSS 4.0: `CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:N/VI:N/VA:L/SC:N/SI:N/SA:N`, from CNA (VulnCheck) (used for this record)
- 3.7 Low, CVSS 3.1: `CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:L`, from CNA (VulnCheck)

- **CISA KEV:** Not listed.
- **EPSS:** 0.0042, the 36th percentile, on 15 Nov 2026: FIRST’s estimate of the chance of exploitation in the next 30 days.

## Timeline

- 26 Oct 2026, 21:52 UTC: [Confirmed by the CVE List](https://www.cve.org/CVERecord?id=CVE-2026-116733)
- 26 Oct 2026, 22:16 UTC: [Confirmed by NVD](https://nvd.nist.gov/vuln/detail/CVE-2026-116733)

## Sources

- [CVE List: CVE-2026-116733](https://www.cve.org/CVERecord?id=CVE-2026-116733)
- [NVD: CVE-2026-116733](https://nvd.nist.gov/vuln/detail/CVE-2026-116733)

### References from the CNA

- <https://github.com/dvidelabs/flatcc/commit/356792dc155a9e685acdfe0ec1e209bdadcb4ab9> (patch)
- <https://github.com/dvidelabs/flatcc> (product)
- <https://github.com/dvidelabs/flatcc/blob/v0.6.4/src/runtime/json_parser.c#L539-L543> (technical-description)
- <https://hackmd.io/@haindpwn/flatcc-json-number-oob-read> (third-party-advisory)
- <https://www.vulncheck.com/advisories/flatcc-through-0.6.4-out-of-bounds-read-via-flatcc-json-parser-number> (third-party-advisory)

Facts on this page come from the CVE List as the CNA published them, with CVSS from the sources named above, CISA KEV and FIRST EPSS. Vendors, products and versions are shown as the CNA wrote them. We don’t reproduce the CVE’s description.

## Check whether this affects you

This CVE names a vendor and product rather than a package, so the lockfile check doesn’t match it. Compare the affected versions above with what you run.

- With the agentprime MCP server (<https://api.agentprime.io/mcp>), `get_advisory` returns this record and `search_advisories` finds related ones. Setup: <https://agentprime.io/mcp.md>
- As JSON: <https://api.agentprime.io/v1/advisories/CVE-2026-116733>
- Everything that needs attention now: <https://agentprime.io/advisories/critical.md>

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The web page: <https://agentprime.io/advisories/CVE-2026-116733/>. Everything for agents: <https://agentprime.io/llms.txt>.