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TI-2026-83424 Aliases CVE-2026-55613

HTTP request smuggling in uhttpd via ubus POST body parse errors

Priority HIGH 70CWE-444Published · Updated

Key facts

Attack vector
Network
Privileges required
None
User interaction
None
Attack complexity
Low
Attack requirements
None
Impact type
—
Confidentiality · integrity · availability
None · Low · None
Fix status
Fixed

Attack profile from CVSS 4.0 · CNA. Fix status from CNA.

Summary

OpenWrt uhttpd before commit 7b1bec45826bd78c8afc993435bdc0f1df2fe399 is affected. A parse error in the ubus POST body handler, uh_ubus_data_send(), leaves part of a JSON body split across TCP segments unread (CWE-444). An unauthenticated remote attacker can smuggle an HTTP request in that unread body, which the server handles as a new request on the same keep-alive connection. A reproducer has been reported.

Written with Claude Haiku 5.5 from the sources below · 2026-11-05

Description from the CNA

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.

Why it matters now

Exploitation Proof of concept CISA SSVC · not in CISA KEV
EPSS 0.00395 33rd percentileScored 2026-11-07
Fix Fixed uhttpd (openwrt): 7b1bec45826bd78c8afc993435bdc0f1df2fe399

SSVC decision points

CISA ADP · SSVC 2.0.3

Exploitation
Poc
Automatable
Yes
Technical impact
Partial

The decision (Track, Attend, Act) also depends on your mission and well-being impact; see CISA's SSVC guide.

Affected products

VendorProductAffected versionsFixed inStatusSource
openwrtuhttpdbefore 7b1bec45826bd78c8afc993435bdc0f1df2fe3997b1bec45826bd78c8afc993435bdc0f1df2fe399Patch availableCNA
  • uhttpd Vendoropenwrt Affected before 7b1bec45826bd78c8afc993435bdc0f1df2fe399 Fixed in 7b1bec45826bd78c8afc993435bdc0f1df2fe399 Patch available CNA

Remediation

Apply repository patches 7b1bec45826bd78c8afc993435bdc0f1df2fe399 and b2285de129b9adc8b12f84f9a27c16c21f2b57a5 to uhttpd.

Written with Claude Haiku 5.5 from the sources below · 2026-11-05

  • Fix · CNA uhttpd (openwrt) Fixed in 7b1bec45826bd78c8afc993435bdc0f1df2fe399

Timeline

  1. 2026-10-30 Threatist record created from CVE-2026-55613
  2. 2026-11-01 Priority changed: MEDIUM → LOW
  3. 2026-11-05 CISA SSVC decision points changed
  4. 2026-11-05 Priority changed: LOW → HIGH

References

Other 3

  • TI-2026-79903 Stack buffer overflow in odhcpd DHCPv6 IA reply handling CVSS 3.1CRITICAL 9.8
  • TI-2024-13053 Improper input validation in MediaTek MT6890, MT7915, MT7916, MT7981, MT7986 CVSS 3.1CRITICAL 9.8
  • TI-2026-79901 Use-after-free in odhcpd DHCPv6 IA handling CVSS 4.0HIGH 8.8
  • TI-2026-48502 OpenWrt luci-app-bmx7 Path Traversal via bmx7-info CVSS 4.0HIGH 8.7
  • TI-2026-44407 luci-app-banip Log Monitor IP Extraction Bypass CVSS 4.0HIGH 8.7
  • TI-2026-51067 luci-app-openvpn Path Traversal RCE via instance_name2 CVSS 4.0CRITICAL 9.4
See all 168 →

Sources

This product uses the NVD API but is not endorsed or certified by the NVD. Sources and licences