# CVE-2026-102077: Denial of service in Junos OS

> An unauthenticated attacker can cause a denial of service on Juniper MX Series devices with SPC3 and source NAT by sending malformed IPv6 packets that exhaust resources.

- **Severity:** High 8.7 (`CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:L/AU:Y/R:U/RE:M`)
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** No
- **Published:** 14 Oct 2026
- **Updated:** 14 Oct 2026
- **Also known as:** GHSA-699j-9vw9-9rmg

## What is CVE-2026-102077?

CVE-2026-102077 is a high-severity denial of service vulnerability in Juniper Networks Junos OS, published on 14 Oct 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.

### Official description

An Improper Check for Unusual or Exceptional Conditions vulnerability in the Packet Forwarding Engine (PFE) of Juniper Networks Junos OS on MX Series with SPC3 allows an unauthenticated, network-based attacker to cause a Denial-of-Service (DoS).

On MX Series with SPC3 line-card and source NAT configuration, when a specific malformed IPv6 packet is received, it is not dropped but instead a session is created and NAT resources are allocated. Continued receipt of such packets will eventually lead to session or resource exhaustion, which will impact all traffic through the device. To recover the device needs to be rebooted.
To monitor session usage, use the following:

show services sessions summary

To monitor source NAT resource usage, use the following: 

show services nat pool

This issue affects Junos OS on MX Series with SPC3:

  *  All versions before 23.2R2-S4;
  *  23.4 versions before 23.4R2-S5;
  *  24.2 versions before 24.2R2.

Weakness: CWE-754 (Improper Check for Unusual or Exceptional Conditions)

## Which versions are affected by CVE-2026-102077?


## How do I fix CVE-2026-102077?

No fix has been published for CVE-2026-102077 yet. Limit exposure of the affected software until one is available.

## Is CVE-2026-102077 being exploited?

There is no known exploitation of CVE-2026-102077 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-102077 and fix it if it is affected.

What it is: CVE-2026-102077 is a high-severity denial of service vulnerability in Juniper Networks Junos OS, published on 14 Oct 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-2026-102077 in the wild and no public exploit code.

Affected product: Juniper Networks Junos OS. 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-2026-102077/ (Markdown: https://insights.sbomify.com/CVE-2026-102077/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-102077
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-102077
- OSV: https://osv.dev/vulnerability/CVE-2026-102077

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-102077/
Summaries are generated and may contain mistakes; the official description above is the record.