OpenWrt uhttpd ubus handler ubus.c uh_ubus_data_send expected behavior violation

CVSS Meta Temp Score
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CTI Interest Score
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7.0$0-$5k2.28-

Summaryinfo

A vulnerability was found in OpenWrt uhttpd. It has been declared as critical. Affected is the function uh_ubus_data_send of the file ubus.c of the component ubus handler. Such manipulation leads to expected behavior violation. This vulnerability is listed as CVE-2026-55613. The attack may be performed from remote. There is no available exploit. It is advisable to implement a patch to correct this issue.

Detailsinfo

A vulnerability, which was classified as critical, has been found in OpenWrt uhttpd (version now known). Affected by this issue is the function uh_ubus_data_send of the file ubus.c of the component ubus handler. The manipulation with an unknown input leads to a expected behavior violation vulnerability. Using CWE to declare the problem leads to CWE-440. A feature, API, or function does not perform according to its specification. Impacted is confidentiality, integrity, and availability. CVE summarizes:

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.

The advisory is shared for download at github.com. This vulnerability is handled as CVE-2026-55613 since 06/17/2026. The exploitation is known to be easy. The attack may be launched remotely. No form of authentication is required for exploitation. There are known technical details, but no exploit is available.

Applying the patch 7b1bec45826bd78c8afc993435bdc0f1df2fe399/b2285de129b9adc8b12f84f9a27c16c21f2b57a5 is able to eliminate this problem.

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Productinfo

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Website

CPE 2.3info

CPE 2.2info

CVSSv4info

VulDB Vector: 🔒
VulDB Reliability: 🔍

CNA CVSS-B Score: 🔒
CNA CVSS-BT Score: 🔒
CNA Vector: 🔒

CVSSv3info

VulDB Meta Base Score: 7.3
VulDB Meta Temp Score: 7.0

VulDB Base Score: 7.3
VulDB Temp Score: 7.0
VulDB Vector: 🔒
VulDB Reliability: 🔍

CVSSv2info

AVACAuCIA
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VectorComplexityAuthenticationConfidentialityIntegrityAvailability
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VulDB Base Score: 🔒
VulDB Temp Score: 🔒
VulDB Reliability: 🔍

Exploitinginfo

Class: Expected behavior violation
CWE: CWE-440 / CWE-436
CAPEC: 🔒
ATT&CK: 🔒

Physical: No
Local: No
Remote: Yes

Availability: 🔒
Status: Not defined
Price Prediction: 🔍
Current Price Estimation: 🔒

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Threat Intelligenceinfo

Interest: 🔍
Active Actors: 🔍
Active APT Groups: 🔍

Countermeasuresinfo

Recommended: Patch
Status: 🔍

0-Day Time: 🔒

Patch: 7b1bec45826bd78c8afc993435bdc0f1df2fe399/b2285de129b9adc8b12f84f9a27c16c21f2b57a5

Timelineinfo

06/17/2026 CVE reserved
10/30/2026 +135 days Advisory disclosed
10/30/2026 +0 days VulDB entry created
10/30/2026 +0 days VulDB entry last update

Sourcesinfo

Product: github.com

Advisory: github.com
Status: Confirmed

CNA: GitHub_M
CVE: CVE-2026-55613 (🔒)

GCVE (CVE): GCVE-0-2026-55613
GCVE (VulDB): GCVE-100-429428

Entryinfo

Created: 10/30/2026 23:17
Changes: 10/30/2026 23:17 (69)
Complete: 🔍
Cache ID: 216::103

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