Executive brief
AG-UI is a protocol library for integrating AI agents into frontend applications. A vulnerability in its Server-Sent Events (SSE) parser component allows remote attackers to cause excessive resource consumption by manipulating the parser's buffer handling, potentially leading to denial of service.
Technical details
The vulnerability exists in the SSE parser component (src/stream/sse_parser.cpp) of ag-ui version 1.0, where the per-event accumulator is not properly counted against the SSE buffer capacity limit. This allows an attacker to send specially crafted SSE messages that bypass buffer constraints, causing unbounded resource consumption. The attack is network-accessible and requires no authentication. The impact is denial of service through resource exhaustion. A patch is available in commit ab6e0bc298996caac2b4b0b3ec0bd8d32a15a186.
Affected products
- ag-ui-protocol ag-ui 1.0
Timeline
- 2026-09-16: disclosed
- 2026-09-16: patched: commit ab6e0bc298996caac2b4b0b3ec0bd8d32a15a186