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.
- 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-2026-102077?
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
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.
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-2026-102077 being exploited?
There is no known exploitation of CVE-2026-102077 in the wild and no public exploit code.
Sources
Also known as GHSA-699j-9vw9-9rmg.