CVE-2026-25791
Published: 09 February 2026
Summary
CVE-2026-25791 is a high-severity Missing Authentication for Critical Function (CWE-306) vulnerability in Bishopfox Sliver. Its CVSS base score is 7.5 (High).
Operationally, exploitation aligns with the MITRE ATT&CK technique Exploit Public-Facing Application (T1190); ranked at the 10.1th percentile by exploit likelihood (below the median); it is not currently listed in the CISA KEV catalog; a public proof-of-concept is referenced.
The strongest mitigations our analysis identified are NIST 800-53 AC-10 (Concurrent Session Control) and SC-5 (Denial-of-service Protection).
Deeper analysis
CVE-2026-25791 is a vulnerability in the Sliver command and control (C2) framework, which uses a custom Wireguard netstack. Prior to version 1.7.0, the DNS C2 listener accepts unauthenticated TOTP bootstrap messages and allocates server-side DNS sessions without validating OTP values, even when the EnforceOTP option is enabled. These sessions are stored without a cleanup or expiry mechanism, allowing resource exhaustion.
An unauthenticated remote actor can exploit this vulnerability by repeatedly sending bootstrap messages to create numerous sessions, resulting in memory exhaustion and denial of service. The CVSS v3.1 base score is 7.5 (AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H), reflecting high availability impact with low attack complexity and no privileges required. It maps to CWE-306 (Missing Authentication for Critical Function) and CWE-400 (Uncontrolled Resource Consumption).
The vulnerability is addressed in Sliver version 1.7.0. Additional details are available in the release notes at https://github.com/BishopFox/sliver/releases/tag/v1.7.0 and the security advisory at https://github.com/BishopFox/sliver/security/advisories/GHSA-wxrw-gvg8-fqjp.
EU & UK References
- 🇪🇺 ENISA EUVD: EUVD-2026-6853
Vulnerability details
Sliver is a command and control framework that uses a custom Wireguard netstack. Prior to 1.7.0, the DNS C2 listener accepts unauthenticated TOTP bootstrap messages and allocates server-side DNS sessions without validating OTP values, even when EnforceOTP is enabled. Because…
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sessions are stored without a cleanup/expiry path in this flow, an unauthenticated remote actor can repeatedly create sessions and drive memory exhaustion. This vulnerability is fixed in 1.7.0.
- CWE(s)
Related Threats
MITRE ATT&CK Enterprise TechniquesAI
Why these techniques?
Unauthenticated remote exploitation of the public DNS C2 listener via repeated bootstrap messages exhausts server resources, directly enabling T1190 (public-facing application exploitation) and T1499.002 (service exhaustion flood for DoS).
CVEs Like This One
Affected Assets
Mitigating Controls
Mitigating Controls (NIST 800-53 r5) AI
Denial-of-service Protection directly mitigates the memory exhaustion DoS by implementing limits and validation on unauthenticated bootstrap messages.
Resource Availability protects system resources like memory from unauthorized consumption caused by repeated unvalidated session allocations.
Concurrent Session Control enforces limits on the number of server-side DNS sessions to prevent exhaustion from unauthenticated bootstrap messages.