---
id: "CVE-2026-117503"
kind: "vulnerability"
aliases: ["CVE-2026-117503"]
title: "a2a-go: REST SSE handler lets remote callers exhaust server resources"
severity: "medium"
cvss: 6.9
epss: null
exploited: false
status: "open"
category: "package"
products: []
ecosystems: []
tags: ["a2a", "go", "package", "self-hosted"]
not_affected_if: ["client-only", "no-rest-sse-handler"]
published_at: "2026-10-27T14:16:35+00:00"
first_seen_at: "2026-10-27T14:32:18+00:00"
updated_at: "2026-10-27T14:33:06+00:00"
sources: [{"source": "nvd", "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-117503", "first_seen_at": "2026-10-27T14:32:18+00:00"}]
---

# a2a-go: REST SSE handler lets remote callers exhaust server resources

The REST SSE handler in a2a-go up to 2.4.0 (a2asrv/rest.go) can be driven into heavy resource consumption by a remote request. An attacker can cause denial of service on a server running the affected version.

_Summary, check and fix written by a model from the sources; labelled as such._

## How to check

- Run `go list -m github.com/a2aproject/a2a-go` in the project and compare the version against `2.4.0`
- Search the lockfile or `go.mod` for `a2aproject/a2a-go` and confirm whether a version at or below `2.4.0` is pinned

## Fix

- Upgrade a2a-go to `2.5.0` or later (commit ff6035bd21e44bb3ee1bfa547885b8c08327fa01 is the patch)
- Rebuild and redeploy any service that imports a2a-go

## Timeline

- 2026-10-27T14:32:18+00:00 nvd https://nvd.nist.gov/vuln/detail/CVE-2026-117503

## From the sources

A vulnerability was determined in a2aproject a2a-go up to 2.4.0. Impacted is an unknown function of the file a2asrv/rest.go of the component REST SSE handler. This manipulation causes resource consumption. It is possible to initiate the attack remotely. Upgrading to version 2.5.0 is recommended to address this issue. Patch name: ff6035bd21e44bb3ee1bfa547885b8c08327fa01. It is recommended to upgrade the affected component.

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_Free to read at a human pace. An API with keys and an MCP server are in preparation; early access: hello@infrastack.ai_