What is CVE-2026-103391?

CVE-2026-103391 is a medium-severity vulnerability in Juniper Networks Session Smart Router, classified under Out-of-bounds Write. CVSS score: 5.3/10. Published 2026-10-28.

How severe is CVE-2026-103391?

Medium severity. CVSS v3 base score is 5.3 out of 10.

Buffer overflow in Juniper Networks Session Smart Router

CVE-2026-103391

An Out-of-bounds Write vulnerability in the SSR TCP proxy/optimization path in Juniper Networks Session Smart Router allows an attacker to corrupt forwarded packet data and potentially cause a data-plane crash via a transit TCP packet with a crafted TCP option length.

Vulnerability class: Buffer Overflow

Published 2026-10-28 · last modified 2026-10-28.

CVSS v3 metric

CVSS v3 base score 5.3 (Medium). Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:N.

EPSS exploit prediction

No EPSS score from FIRST.org yet. New CVEs usually get one within a few days; no score means no signal yet, not low risk. How EPSS works.

Affected products

Juniper Networks Session Smart Router

Weakness classification (CWE)

CWE-787 — Out-of-bounds Write

References

supportportal.juniper.net/JSA112183 (vendor-advisory)

Frequently asked questions

What is CVE-2026-103391?: CVE-2026-103391 is a medium-severity vulnerability in Juniper Networks Session Smart Router, classified under Out-of-bounds Write. CVSS score: 5.3/10. Published 2026-10-28.
How severe is CVE-2026-103391?: Medium severity. CVSS v3 base score is 5.3 out of 10.