# CVE-2026-101101: ag-ui JSON.parse uncaught exception in middleware

Source: https://junglewise.ai/threats/cve-2026-101101-a-vulnerability-has-been-found-in-ag-ui-protocol-ag-ui-up-to  
Publisher: Junglewise Threat Intelligence, https://junglewise.ai/threats  
Published: 2026-09-28. Updated: 2026-09-28  
License: CC BY 4.0 with a link back

CVE-2026-101101 · Severity: medium · CVSS 4.3 · Published 2026-09-28

AG-UI is a protocol library that enables agents to interact with frontend applications. The vulnerability allows remote attackers to trigger an uncaught exception by sending malformed JSON to the middleware component, potentially causing application crashes or denial of service.

Technologies: [Ag-Ui-Protocol Ag-Ui](https://junglewise.ai/threats/technologies/ag-ui). Vendors: [Ag-Ui-Protocol](https://junglewise.ai/threats/vendors/ag-ui-protocol).

## Quick answers

**Is CVE-2026-101101 exploited in the wild?** No. Junglewise Threat Intelligence has no report of CVE-2026-101101 being exploited in the wild.

**How severe is CVE-2026-101101?** Medium severity, with a CVSS score of 4.3, published 28 September 2026.

**Which products and versions are affected?** Ag-Ui-Protocol Ag-Ui up to 2026-09-07.

**Is there a fix for CVE-2026-101101?** A patch was published on 2026-09-08: Version 2026-09-08 or later addresses the issue Junglewise finds every place you run it, drafts the upgrade and applies it once you approve.

**How is CVE-2026-101101 attacked?** It is attacked over the network, in a software library.

**Am I affected by CVE-2026-101101?** Check whether you run Ag-Ui-Protocol Ag-Ui at an affected version. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.

## Technical details

An uncaught exception vulnerability exists in the JSON.parse function within the legacy/convert.ts middleware component of AG-UI. The vulnerability can be exploited remotely without authentication by sending malformed JSON data. The issue has been patched in version 2026-09-08 to properly guard JSON.parse and surface errors as stream errors rather than uncaught exceptions.

## Affected products

- ag-ui-protocol ag-ui up to 2026-09-07

## Timeline

- 2026-09-28: disclosed
- 2026-09-08: patched: Version 2026-09-08 or later addresses the issue

## References

- [https://github.com/ag-ui-protocol/ag-ui/](https://github.com/ag-ui-protocol/ag-ui/)
- [https://github.com/ag-ui-protocol/ag-ui/commit/30f8c794d5b73df5c610153043db502b2cc106cc](https://github.com/ag-ui-protocol/ag-ui/commit/30f8c794d5b73df5c610153043db502b2cc106cc)

## Related threats

- [ag-ui-protocol ag-ui resource exhaustion in interrupt expiry](https://junglewise.ai/threats/cve-2026-120237-a-flaw-has-been-found-in-ag-ui-protocol-ag-ui-up-to-0-0-58)
- [ag-ui Transport Decoder Handler improper input validation](https://junglewise.ai/threats/cve-2026-120236-a-vulnerability-was-detected-in-ag-ui-protocol-ag-ui-up-to-0-0)
- [ag-ui SSE parser resource exhaustion](https://junglewise.ai/threats/cve-2026-120235-a-security-vulnerability-has-been-detected-in-ag-ui-protocol-ag)
- [ag-ui HTTP Transport unbounded response buffering](https://junglewise.ai/threats/cve-2026-120234-a-weakness-has-been-identified-in-ag-ui-protocol-ag-ui-up-to-0-0)
- [ag-ui HttpAgent credential and request body forwarding via redirect](https://junglewise.ai/threats/cve-2026-120233-a-security-flaw-has-been-discovered-in-ag-ui-protocol-ag-ui-up)