# CVE-2026-33778: Junos OS: SRX Series, MX Series: When a specifically malformed first ISAKMP packet is received kmd/iked crashes

> An unauthenticated attacker can crash the IPsec daemon by sending a malformed ISAKMP packet, preventing new VPN connections on Juniper SRX and MX devices.

- **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/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:** 9 Apr 2026
- **Updated:** 10 Apr 2026
- **Also known as:** GHSA-q559-6pc6-gxfh

## What is CVE-2026-33778?

CVE-2026-33778 is a high-severity denial of service vulnerability in Juniper Junos, published on 9 Apr 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.

### Official description

An Improper Validation of Syntactic Correctness of Input vulnerability in the  IPsec library used by kmd and iked of Juniper Networks Junos OS on SRX Series and MX Series allows an unauthenticated, network-based attacker to cause a complete Denial-of-Service (DoS).

If an affected device receives a specifically malformed first ISAKMP packet from the initiator, the kmd/iked process will crash and restart, which momentarily prevents new security associations (SAs) for from being established. Repeated exploitation of this vulnerability causes a complete inability to establish new VPN connections.

This issue affects Junos OS on 

SRX Series and MX Series:

  *  all versions before 22.4R3-S9,
  *  23.2 version before 23.2R2-S6,
  *  23.4 version before 23.4R2-S7,
  *  24.2 versions before 24.2R2-S4,
  *  24.4 versions before 24.4R2-S3,
  *  25.2 versions before 25.2R1-S2, 25.2R2.

Weakness: CWE-1286 (Improper Validation of Syntactic Correctness of Input)

## Which versions are affected by CVE-2026-33778?

It affects 1 product.


Products: Juniper Junos.

## How do I fix CVE-2026-33778?

No fix has been published for CVE-2026-33778 yet. Limit exposure of the affected software until one is available.

## Is CVE-2026-33778 being exploited?

There is no known exploitation of CVE-2026-33778 in the wild and no public exploit code.

## Other vulnerabilities in Juniper Junos

- [CVE-2023-36845](https://insights.sbomify.com/CVE-2023-36845/): Juniper Junos OS EX Series and SRX Series PHP External Variable Modification (critical 9.8, exploited in the wild)
- [CVE-2020-1631](https://insights.sbomify.com/CVE-2020-1631/): Juniper Junos OS Path Traversal (high 8.8, exploited in the wild)
- [CVE-2025-21590](https://insights.sbomify.com/CVE-2025-21590/): Juniper Junos OS Improper Isolation or Compartmentalization (medium 6.7, exploited in the wild)
- [CVE-2023-36851](https://insights.sbomify.com/CVE-2023-36851/): Juniper Junos OS SRX Series Missing Authentication for Critical Function (medium 5.3, exploited in the wild)
- [CVE-2023-36844](https://insights.sbomify.com/CVE-2023-36844/): Juniper Junos OS EX Series PHP External Variable Modification (medium 5.3, exploited in the wild)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-33778 and fix it if it is affected.

What it is: CVE-2026-33778 is a high-severity denial of service vulnerability in Juniper Junos, published on 9 Apr 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-2026-33778 in the wild and no public exploit code.

Affected product: Juniper Junos. 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-2026-33778/ (Markdown: https://insights.sbomify.com/CVE-2026-33778/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-33778
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-33778
- OSV: https://osv.dev/vulnerability/CVE-2026-33778

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-33778/
Summaries are generated and may contain mistakes; the official description above is the record.