CVE-2026-0392 Overview
CVE-2026-0392 affects eParakstītājs 3.0 for Windows before version 1.10.0, a Latvian electronic signing client. The application fetches update descriptors and installers over TLS but disables all certificate validation. A permissive TrustManager and a HostnameVerifier that always returns true allow any certificate. The client also skips digital signature verification on the update descriptor and never validates the Authenticode signature or checksum of the downloaded installer. An attacker positioned on the network path to www.eparaksts.lv can serve a malicious installer that the client executes, yielding arbitrary code execution on the victim host [CWE-295].
Critical Impact
Man-in-the-middle attackers on the same network segment can achieve arbitrary code execution by hijacking the auto-update channel.
Affected Products
- eParakstītājs 3.0 for Windows versions prior to 1.10.0
- Auto-update component fetching descriptors from www.eparaksts.lv
- Deployments relying on default TLS trust configuration in the client
Discovery Timeline
- 2026-08-03 - CVE-2026-0392 published to NVD
- 2026-08-05 - Last updated in NVD database
Technical Details for CVE-2026-0392
Vulnerability Analysis
The vulnerability stems from improper certificate validation in the auto-update mechanism of eParakstītājs 3. On each launch, the client contacts www.eparaksts.lv to retrieve an XML update descriptor over TLS. The TLS stack is initialized with a TrustManager implementation that accepts any X.509 certificate chain without validation. The paired HostnameVerifier unconditionally returns true, defeating name checking. This combination reduces TLS to opportunistic encryption without authentication.
Compounding the transport weakness, the client performs no signature verification on the update descriptor itself. The descriptor points to an installer URL, and the client downloads and executes that installer without validating its Authenticode signature or comparing a cryptographic checksum against a trusted value. Any attacker capable of redirecting or intercepting traffic to the update host can substitute an arbitrary Windows executable, which runs with the privileges of the invoking user.
Root Cause
The root cause is a chain of missing integrity controls categorized under [CWE-295] Improper Certificate Validation. Trust decisions were delegated to code paths that unconditionally return success, and no compensating out-of-band signature checks were performed on either the descriptor or the installer payload.
Attack Vector
Exploitation requires an adjacent-network position that lets the attacker impersonate www.eparaksts.lv. This includes ARP spoofing on shared Wi-Fi, rogue access points, compromised routers, or DNS hijacking. The attacker serves a crafted XML descriptor over TLS with any certificate, points the installerUrl at an attacker-hosted executable, and waits for the target to launch the application. The client downloads the binary and executes it, producing code execution in the user context.
No verified public exploit code is available. See the Offseq research writeup and the CERT.LV vulnerability report for technical detail.
Detection Methods for CVE-2026-0392
Indicators of Compromise
- Unexpected child processes spawned by the eParakstītājs updater shortly after application launch
- Installer binaries written to temporary directories that lack a valid Authenticode signature from Latvijas Valsts radio un televīzijas centrs (LVRTC)
- DNS resolutions for www.eparaksts.lv pointing to non-official IP ranges
- Outbound TLS connections to www.eparaksts.lv presenting certificates from unexpected issuers
Detection Strategies
- Alert on any executable download initiated by the eParakstītājs process tree followed by immediate execution of a non-signed binary
- Correlate DNS answers for www.eparaksts.lv against a known-good IP allow list maintained by the security team
- Inspect TLS session metadata to flag certificates for the eParaksts domain that chain to unexpected roots
Monitoring Recommendations
- Log endpoint process creation events with parent-child relationships involving the eParakstītājs updater
- Capture NetFlow or Zeek ssl.log entries for connections to eParaksts infrastructure and review certificate fingerprints
- Track file creation events for .exe and .msi files in the application's update staging directory
How to Mitigate CVE-2026-0392
Immediate Actions Required
- Upgrade eParakstītājs 3 to version 1.10.0 or later on every Windows endpoint
- Inventory endpoints that have executed the vulnerable version and review them for anomalous child processes
- Restrict use of the application on untrusted networks such as public Wi-Fi until patching is complete
Patch Information
The vendor released version 1.10.0, which addresses the certificate validation and update integrity issues. Refer to the eParaksts update announcement for release notes and download links.
Workarounds
- Block outbound access from endpoints to www.eparaksts.lv on untrusted networks until the client is updated
- Require VPN connectivity to a trusted network segment before permitting the application to launch
- Use application allow-listing to prevent execution of unsigned binaries dropped by the updater
# Example: enforce host pinning for eParaksts update host via hosts file
# Replace <official-ip> with the current published IP for www.eparaksts.lv
<official-ip> www.eparaksts.lv
Disclaimer: This content was generated using AI. While we strive for accuracy, please verify critical information with official sources.
