# CVE-2026-120235: ag-ui SSE parser resource exhaustion

Source: https://junglewise.ai/threats/cve-2026-120235-a-security-vulnerability-has-been-detected-in-ag-ui-protocol-ag  
Publisher: Junglewise Threat Intelligence, https://junglewise.ai/threats  
Published: 2026-11-01. Updated: 2026-11-01  
License: CC BY 4.0 with a link back

CVE-2026-120235 · Severity: medium · CVSS 4.3 · Published 2026-11-01

ag-ui is a framework that brings AI agents into frontend applications. A flaw in its Server-Sent Events (SSE) parser allows an attacker to send specially crafted data over the network that causes excessive resource consumption, potentially leading to application slowdown or unavailability. An attacker can exploit this remotely without authentication.

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-2026-120235 exploited in the wild?** No. Junglewise Threat Intelligence has no report of CVE-2026-120235 being exploited in the wild.

**How severe is CVE-2026-120235?** Medium severity, with a CVSS score of 4.3, published 1 November 2026.

**Which products and versions are affected?** Ag-Ui-Protocol Ag-Ui up to 0.0.58.

**Is there a fix for CVE-2026-120235?** Yes: fixed in commit 9e7b2b00bce215bbf731f1e6094f63812527c432 onward. Junglewise finds every place you run it, drafts the upgrade and applies it once you approve.

**How is CVE-2026-120235 attacked?** It is attacked over the network.

**Am I affected by CVE-2026-120235?** 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.

## How to fix

- Fixed in commit 9e7b2b00bce215bbf731f1e6094f63812527c432 onward

## Technical details

The vulnerability exists in the parseSSEStream function of the SSE parser component (sdks/typescript/packages/client/src/transform/sse.ts). It allows unbounded buffer allocation when processing SSE frames, leading to denial-of-service through resource exhaustion. The attack is network-based and requires no authentication or user interaction; the fix caps the buffer size to prevent uncontrolled memory consumption.

## Affected products

- ag-ui-protocol ag-ui up to 0.0.58

## Timeline

- 2026-11-01: disclosed
- 2026-09-09: patched

## 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/9e7b2b00bce215bbf731f1e6094f63812527c432](https://github.com/ag-ui-protocol/ag-ui/commit/9e7b2b00bce215bbf731f1e6094f63812527c432)

## 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 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)
- [ag-ui JSON.parse uncaught exception in middleware](https://junglewise.ai/threats/cve-2026-101101-a-vulnerability-has-been-found-in-ag-ui-protocol-ag-ui-up-to)