---
id: "CVE-2026-55613"
kind: "vulnerability"
aliases: ["CVE-2026-55613"]
title: "uhttpd: split POST body lets smuggled HTTP requests run on keep-alive"
severity: "medium"
cvss: 6.9
epss: null
exploited: false
status: "open"
category: "infrastructure"
products: []
ecosystems: []
tags: ["infrastructure", "openwrt", "routers", "self-hosted", "ubus", "uhttpd"]
not_affected_if: ["no-keep-alive-proxy", "ubus-disabled"]
published_at: "2026-10-30T22:16:55+00:00"
first_seen_at: "2026-10-30T22:25:56+00:00"
updated_at: "2026-10-30T22:27:16+00:00"
sources: [{"source": "nvd", "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-55613", "first_seen_at": "2026-10-30T22:25:56+00:00"}]
---

# uhttpd: split POST body lets smuggled HTTP requests run on keep-alive

uhttpd, the small HTTP server used on OpenWrt routers, mishandles a POST /ubus JSON body that arrives across several TCP segments. An attacker can get a second HTTP request hidden in the unread body to be processed as a new request on the same keep-alive connection, which is request smuggling.

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

## How to check

- Check whether uhttpd is running with ubus enabled on the device or server, for example by reviewing the uhttpd config for `ubus_prefix` or `ubus_cors` settings (unknown whether the sources name a specific default).
- Confirm the installed uhttpd version and compare it to the repository patches 7b1bec45826bd78c8afc993435bdc0f1df2fe399 and b2285de129b9adc8b12f84f9a27c16c21f2b57a5.
- Check whether uhttpd sits behind a proxy or CDN that reuses keep-alive connections to it.

## Fix

- Apply the repository patches 7b1bec45826bd78c8afc993435bdc0f1df2fe399 and b2285de129b9adc8b12f84f9a27c16c21f2b57a5 to uhttpd.
- Fixed release versions: unknown; the sources do not state them.

## Timeline

- 2026-10-30T22:25:56+00:00 nvd https://nvd.nist.gov/vuln/detail/CVE-2026-55613

## From the sources

uhttpd is a small HTTP server. In unpatched repository snapshots, `uh_ubus_data_send()` in `ubus.c` can desynchronize HTTP request boundaries when a `POST /ubus` JSON body arrives in multiple TCP segments. An initial segment completing a JSON object sets `du->jsobj`; a later segment takes the existing-object parse-error path and returns zero bytes consumed. The caller neither drains the remaining declared `Content-Length` nor sets `connection_close`. An HTTP request embedded in the unread body suffix is consequently processed as a new request on the same keep-alive connection. The reported reproducer returned a JSON-RPC parse error followed by a second HTTP response. This application-layer body-handler flaw is distinct from Transfer-Encoding header case handling and chunk-length state reset, and affects deployments enabling ubus, including the default OpenWrt configuration and potential proxy/CDN deployments. Repository patches 7b1bec45826bd78c8afc993435bdc0f1df2fe399 and b2285de129b9adc8b12f84f9a27c16c21f2b57a5 address this issue.

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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_