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.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Over the internet
- Victim action needed
- Not needed
- Fix
- None listed
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
Which versions are affected by CVE-2026-33778?
It affects 1 product.
Products include 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.
Upgrade, then put limits on request size, rate and nesting depth so one client cannot exhaust the service. More about Denial of service.
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 Juniper Junos OS EX Series and SRX Series PHP External Variable Modification
- CVE-2020-1631 Juniper Junos OS Path Traversal
- CVE-2025-21590 Juniper Junos OS Improper Isolation or Compartmentalization
- CVE-2023-36851 Juniper Junos OS SRX Series Missing Authentication for Critical Function
- CVE-2023-36844 Juniper Junos OS EX Series PHP External Variable Modification
Sources
Also known as GHSA-q559-6pc6-gxfh.