CVE-2026-18895 Overview
CVE-2026-18895 is a stack-based buffer overflow in the UTT HiPER 1250GW router affecting firmware versions up to 3.2.7-210907-180535. The flaw resides in the strcpy call within the /goform/APSecurity_5g handler, where the cipher argument is copied to a fixed-size stack buffer without bounds checking. A remote authenticated attacker can send a crafted request to overflow the stack buffer, corrupt saved return addresses, and achieve arbitrary code execution on the device. Public exploit details have been released, and the vendor did not respond to disclosure attempts, leaving affected devices without an official patch.
Critical Impact
Remote exploitation of the /goform/APSecurity_5g endpoint enables attackers to compromise router integrity, availability, and confidentiality, potentially pivoting into internal networks.
Affected Products
- UTT HiPER 1250GW router
- Firmware versions up to and including 3.2.7-210907-180535
- Web management interface handler /goform/APSecurity_5g
Discovery Timeline
- 2026-08-05 - CVE-2026-18895 published to NVD
- 2026-08-05 - Last updated in NVD database
Technical Details for CVE-2026-18895
Vulnerability Analysis
The vulnerability is a classic stack-based buffer overflow classified under [CWE-119] (Improper Restriction of Operations within the Bounds of a Memory Buffer). The /goform/APSecurity_5g endpoint handles wireless security configuration for the 5 GHz radio. When the endpoint processes the cipher HTTP parameter, it invokes strcpy to copy the user-supplied value into a fixed-size local buffer.
Because strcpy copies until it encounters a null terminator, an attacker-controlled cipher value longer than the destination buffer overwrites adjacent stack memory. This includes saved registers and the function return address. Successful exploitation lets an attacker redirect execution flow and run arbitrary code with the privileges of the web server process on the router.
Root Cause
The root cause is the unbounded use of strcpy on attacker-controlled input inside a web request handler. The firmware does not validate the length of the cipher parameter before copying it, and it does not use safer alternatives such as strncpy or strlcpy with an explicit length constraint. No stack canary or address space layout randomization protection is documented for this embedded platform.
Attack Vector
The attack vector is network-based against the router's HTTP management interface. An attacker with low-privilege authenticated access to the web UI submits a POST request to /goform/APSecurity_5g containing an oversized cipher value. The request triggers the overflow inside the request handler and corrupts the stack frame. Public disclosure of the exploit details, referenced in the GitHub CVE Information and VulDB Vulnerability #385930, lowers the barrier for opportunistic exploitation.
No verified proof-of-concept code is reproduced here. Refer to the linked advisories for technical detail.
Detection Methods for CVE-2026-18895
Indicators of Compromise
- HTTP POST requests to /goform/APSecurity_5g containing abnormally long cipher parameter values, particularly values exceeding typical WPA cipher identifiers such as AES, TKIP, or AES-TKIP.
- Unexpected reboots, crashes, or watchdog resets of the UTT HiPER 1250GW router coinciding with management interface activity.
- Outbound connections from the router to unknown hosts, indicating post-exploitation implant activity.
Detection Strategies
- Inspect web server access logs on the router for requests targeting /goform/APSecurity_5g with request body sizes that deviate from baseline configuration traffic.
- Deploy network intrusion detection signatures that flag POST requests to the vulnerable endpoint containing cipher argument lengths beyond a safe threshold, for example 32 bytes.
- Correlate router administrative session logins with subsequent unusual configuration change requests to identify credential misuse.
Monitoring Recommendations
- Forward router syslog and HTTP access telemetry to a centralized logging platform for retention and correlation.
- Monitor for repeated authentication attempts against the router management interface from external or untrusted internal sources.
- Alert on any traffic originating from the router that does not match expected management or DNS patterns.
How to Mitigate CVE-2026-18895
Immediate Actions Required
- Restrict access to the router web management interface to trusted management subnets only, blocking WAN-side administration.
- Change default and shared administrator credentials on all UTT HiPER 1250GW devices to reduce the pool of attackers who meet the low-privilege precondition.
- Segment the router management VLAN from user and guest networks to limit lateral exposure.
- Evaluate replacement of the affected model where feasible, given the absence of vendor response.
Patch Information
No vendor patch is available. According to the CVE record, the vendor was contacted early during disclosure but did not respond. Organizations should track the VulDB CVE #2026-18895 entry for updates and consider decommissioning the device if a fix is not released.
Workarounds
- Disable remote HTTP and HTTPS administration on the WAN interface, permitting configuration only from a wired LAN management workstation.
- Place an upstream firewall access control list in front of the router that denies inbound traffic to the management port from untrusted networks.
- Rotate wireless configuration credentials and audit administrator accounts to remove any unused or shared logins that could satisfy the authentication requirement.
Disclaimer: This content was generated using AI. While we strive for accuracy, please verify critical information with official sources.
