Steve (Rancher): Missing TLS certificate verification enables man-in-the-middle attacks
Summary
Steve, a Go library used by Rancher for its user interface and request proxying, did not verify the certificate of remote servers during TLS connections by default. An attacker in a network position to intercept traffic could impersonate a server and attack services that use Steve. According to the advisory, an attacker needs a privileged foothold in Rancher's local cluster and the non-default setting ui-offline-preferred set to remote to take over the Rancher UI.
Affected
- Steve (Go module github.com/rancher/steve) 0.2.0 to before 0.2.1
- Steve 0.3.0 to before 0.3.3
- Steve 0.4.0 to before 0.4.4
- Steve 0.5.0 to before 0.5.13
- Default configuration of the affected versions is not vulnerable according to the CNA record; the issue is exploitable with the non-default ui-offline-preferred setting in Rancher.
Fixed in
- Steve v0.2.1
- Steve v0.3.3
- Steve v0.4.4
- Steve v0.5.13
- Rancher release mapping: Unknown.
Workaround
- Keep the default ui-offline-preferred setting (dynamic) instead of remote.
- If you cannot upgrade, use Steve only to connect to trusted servers.
- These measures are interim only; upgrading is the fix.
Exploitation
- No public exploitation known.
- CISA SSVC: exploitation none, automatable no, technical impact total.
- Not listed in CISA KEV.
- EPSS score: 0.00329.
Our recommendation
- Check whether Rancher or the Steve Go module is used in your environment, including in-house Go tools (go.mod).
- Upgrade Steve to a fixed version or update Rancher to a release that includes it; confirm the Rancher release with the SUSE advisories.
- Verify that ui-offline-preferred is not set to remote.
- Restrict who can create services in Rancher's local cluster.
Public exploits
PoC-in-GitHub, Metasploit and Exploit-DB list nothing for this CVE.
Research sources
- GitHub Security Advisory GHSA-95fc-g4gj-mqmx github.com
- SUSE Bugzilla CVE-2023-32198 bugzilla.suse.com
- GitLab Advisory Database (Go module steve) advisories.gitlab.com
- Go vulnerability database GO-2025-3648 pkg.go.dev
- OSV GHSA-95fc-g4gj-mqmx osv.dev
- NVD mirror (vulners) CVE-2023-32198 vulners.com
Researched and written up in English and German by an AI (Claude by Anthropic) based on NVD, CISA, EPSS and the sources listed. The vendor information is authoritative. Researched on 1 Nov 2026, 21:20.
Original description (NVD)
A vulnerability has been identified in Steve where by default it was using an insecure option that did not validate the certificate presented by the remote server while performing a TLS connection. This could allow the execution of a man-in-the-middle (MitM) attack against services using Steve.
Sources
The tracker combines official, freely usable data sources – updated continuously:
- NVD (NIST) – CVEs, rating (CVSS), affected products
- CISA KEV – vulnerabilities confirmed by CISA as actively exploited
- CISA Vulnrichment – CISA assessment (SSVC) in the official CVE record
- FIRST EPSS – probability of exploitation
- Microsoft MSRC – Patch Tuesday: vulnerabilities, severity, updates
- PoC-in-GitHub – public proof-of-concept repositories
- Metasploit (Rapid7) – modules of the Metasploit Framework
- Exploit-DB (OffSec) – archive of public exploits (links only)
- Patch days: official vendor pages (linked per vendor) (Vendor patch days)
This product uses data from the NVD API but is not endorsed or certified by the NVD. EPSS data © FIRST.org.
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