# CVE-2026-25791: Sliver has a DNS C2 OTP Bypass Allows Unauthenticated Session Flooding and Denial of Service

> Unauthenticated attackers can flood Sliver C2 server with DNS sessions, causing memory exhaustion and denial of service.

- **Severity:** High 7.5 (`CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H`)
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** Yes
- **Published:** 9 Feb 2026
- **Updated:** 10 Feb 2026
- **Also known as:** GHSA-wxrw-gvg8-fqjp, GO-2026-4466

## What is CVE-2026-25791?

CVE-2026-25791 is a high-severity denial of service vulnerability in BishopFox sliver, published on 9 Feb 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.

### Official description

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 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.

Weakness: CWE-400 (Uncontrolled Resource Consumption), CWE-306 (Missing Authentication for Critical Functionality)

## Which versions are affected by CVE-2026-25791?

3 open source packages ship an affected version, including github.com/bishopfox/sliver. It affects 1 product.


| Package | Ecosystem | Affected | Fixed in |
| --- | --- | --- | --- |
| `github.com/bishopfox/sliver` | Go | All versions | None |
| `github.com/bishopfox/sliver` | Go | All versions | 1.6.12 |
| `github.com/bishopfox/sliver` | Go | All versions | 1.6.12 |

Products: Bishopfox Sliver.

## How do I fix CVE-2026-25791?

Upgrade github.com/bishopfox/sliver to 1.6.12 or later.

## Is CVE-2026-25791 being exploited?

There is no known exploitation of CVE-2026-25791 in the wild and no public exploit code.

## Other vulnerabilities in BishopFox sliver

- [CVE-2023-34758](https://insights.sbomify.com/CVE-2023-34758/): Silver vulnerable to MitM attack against implants due to a cryptography vulnerability (high 8.1)
- [CVE-2025-27090](https://insights.sbomify.com/CVE-2025-27090/): Server-Side Request Forgery (SSRF) in sliver teamserver (medium 6.9)
- [CVE-2026-25760](https://insights.sbomify.com/CVE-2026-25760/): Website Path Traversal / Arbitrary File Read (Authenticated) in Sliver (medium 6.5)
- [CVE-2026-34227](https://insights.sbomify.com/CVE-2026-34227/): Sliver One-Click Remote Access: Insecure CORS & Unauthenticated MCP Interface (medium 5.9)
- [CVE-2026-32941](https://insights.sbomify.com/CVE-2026-32941/): Sliver Vulnerable to Authenticated OOM via Memory Exhaustion in mTLS/WireGuard Transports (medium 5.7)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-25791 and fix it if it is affected.

What it is: CVE-2026-25791 is a high-severity denial of service vulnerability in BishopFox sliver, published on 9 Feb 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.
Exploitation: There is no known exploitation of CVE-2026-25791 in the wild and no public exploit code.

Affected packages and fixed versions:
- github.com/bishopfox/sliver (Go): affected all versions; no fix listed
- github.com/bishopfox/sliver (Go): affected all versions; fixed in 1.6.12
- github.com/bishopfox/sliver (Go): affected all versions; fixed in 1.6.12

Task:
1. Search the dependency manifests and lockfiles (for example package.json, package-lock.json, requirements.txt, poetry.lock, uv.lock, pom.xml, build.gradle, go.mod, Cargo.lock, Gemfile.lock) and any Dockerfiles for the affected packages, including transitive dependencies.
2. If an affected version is in use, upgrade it to the fixed version for its release line with the project's package manager, so the lockfile is regenerated. Prefer the smallest upgrade that fixes it.
3. If there is no fix, or the upgrade would break the build, do not guess: explain the risk and the safest workaround instead.
4. Run the tests and summarise what changed and why.
5. If nothing in the project is affected, say so and change nothing.

Reference: https://insights.sbomify.com/CVE-2026-25791/ (Markdown: https://insights.sbomify.com/CVE-2026-25791/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-25791
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-25791
- OSV: https://osv.dev/vulnerability/CVE-2026-25791

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-25791/
Summaries are generated and may contain mistakes; the official description above is the record.