# CVE-2015-7871: Auth bypass in n/a

> Remote attackers can bypass authentication in the NTP daemon by sending crafted Crypto-NAK packets, compromising time synchronization integrity.

- **Severity:** Critical 9.8 (`CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/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:** 7 Aug 2017
- **Updated:** 6 Aug 2024
- **Also known as:** DEBIAN-CVE-2015-7871, GHSA-mxc3-mjx4-gjc9, UBUNTU-CVE-2015-7871

## What is CVE-2015-7871?

CVE-2015-7871 is a critical authentication bypass vulnerability in Debian Debian Linux, published on 7 Aug 2017. An attacker can exploit it over the internet without logging in, with no action from the victim.

### Official description

Crypto-NAK packets in ntpd in NTP 4.2.x before 4.2.8p4, and 4.3.x before 4.3.77 allows remote attackers to bypass authentication.

Weakness: CWE-287 (Improper Authentication)

## Which versions are affected by CVE-2015-7871?

It affects 7 products.


Products: Debian Debian Linux, Netapp Clustered Data Ontap, Netapp Data Ontap, Netapp Oncommand Balance, Netapp Oncommand Performance Manager, Netapp Oncommand Unified Manager, Ntp Ntp.

## How do I fix CVE-2015-7871?

Upgrade to a fixed version.

## Is CVE-2015-7871 being exploited?

It is not confirmed as exploited in the wild, but public exploit code for CVE-2015-7871 exists.

Public exploit code:

- NTP "NAK to the Future" (metasploit)

## Other vulnerabilities in Debian Debian Linux

- [CVE-2015-3306](https://insights.sbomify.com/CVE-2015-3306/): ProFTPD Improper Access Control (critical 10.0, exploited in the wild)
- [CVE-2025-49113](https://insights.sbomify.com/CVE-2025-49113/): RoundCube Webmail Deserialization of Untrusted Data (critical 9.9, exploited in the wild)
- [CVE-2026-24061](https://insights.sbomify.com/CVE-2026-24061/): GNU InetUtils Argument Injection (critical 9.8, exploited in the wild)
- [CVE-2025-39682](https://insights.sbomify.com/CVE-2025-39682/): Linux Kernel Improper Check for Unusual or Exceptional Conditions (critical 9.8, exploited in the wild)
- [CVE-2024-9680](https://insights.sbomify.com/CVE-2024-9680/): Mozilla Firefox Use-After-Free (critical 9.8, exploited in the wild)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2015-7871 and fix it if it is affected.

What it is: CVE-2015-7871 is a critical authentication bypass vulnerability in Debian Debian Linux, published on 7 Aug 2017. An attacker can exploit it over the internet without logging in, with no action from the victim.
Exploitation: It is not confirmed as exploited in the wild, but public exploit code for CVE-2015-7871 exists.

Affected product: Debian Debian Linux. No package-level version data is available, so check the vendor advisory linked from the reference page.

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-2015-7871/ (Markdown: https://insights.sbomify.com/CVE-2015-7871/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2015-7871
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2015-7871
- OSV: https://osv.dev/vulnerability/CVE-2015-7871

---
From sbomify Insights: https://insights.sbomify.com/CVE-2015-7871/
Summaries are generated and may contain mistakes; the official description above is the record.