Twonky Server: Unprotected Alternate Channel
CVE-2025-13315 is a critical-severity unprotected alternate channel vulnerability in Twonky Server from Lynxtechnology, with a CVSS 3.1 base score of 9.8 out of 10. It can be exploited remotely over the network by an unauthenticated attacker, without any action from a user. Affected Twonky Server versions: 8.5.2. The record does not name a fixed version, so check the vendor advisory. There is no confirmed exploitation so far. EPSS estimates a 31.2% chance of exploitation within 30 days, which is in the top 1.7% of all scored CVEs.
Critical severity: a successful attack would have severe impact.
What to do
- Check which version of Twonky Server you run against the affected versions below, and install the vendor's latest release.
- Until you can update, restrict network access to the affected service so it is not reachable from untrusted networks.
Affected products and versions
| Vendor | Product | Affected versions | Fixed in |
|---|---|---|---|
| Lynxtechnology | Twonky Server | 8.5.2 | Not stated |
Version data comes from the organisation that assigned the CVE. Confirm against the vendor advisory before deciding you are unaffected.
How the severity score breaks down
- Attack vector
- NetworkCan be exploited remotely over a network, including the internet.
- Attack complexity
- LowNo special conditions are needed; the attack works reliably.
- Privileges required
- NoneNo account or login is needed.
- User interaction
- NoneNo action by a victim is required.
- Scope
- UnchangedImpact stays within the vulnerable component.
- Confidentiality
- HighAll data handled by the component can be read.
- Integrity
- HighData or code can be modified at will.
- Availability
- HighThe component can be taken down completely.
Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H. Scored by NVD.
| Scoring system | Score | Severity | Scored by |
|---|---|---|---|
| CVSS 4.0 | 9.3 | Critical | CNA (rapid7.com) |
| CVSS 3.1 | 9.8 | Critical | NVD |
Official description
Twonky Server 8.5.2 on Linux and Windows is vulnerable to an access control flaw. An unauthenticated attacker can bypass web service API authentication controls to leak a log file and read the administrator's username and encrypted password.
Source: the CVE record as published by its numbering authority, via NVD and CVE.org.
The underlying weakness: Unprotected Alternate Channel
The product protects a primary channel, but it does not use the same level of protection for an alternate channel.
How developers prevent this class of flaw
- Identify all alternate channels and use the same protection mechanisms that are used for the primary channels.
More Unprotected Alternate Channel vulnerabilities (CWE-420)
Timeline
- CVE record published.
- CISA published its SSVC assessment (exploitation: none, automatable: yes, technical impact: total).
- Record last changed materially (score, affected products, status or references).
References
Technical write-ups (may include proof of concept)
- rapid7.com/blog/post/cve-2025-13315-cve-2025-13316-critical-twonky-server-authentication-bypass-not-fixed/Exploit, Third Party Advisory
Other vulnerabilities in Twonky Server
- 8.1 High severity
Recent Unprotected Alternate Channel vulnerabilities
- 8.0 High severity
- 8.8 High severity
- 7.4 High severity
- 9.8 Critical severity
CrushFTP Unprotected Alternate Channel Exploited
- 9.9 Critical severity
- 7.8 High severity
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