CVE-2026-103391 Session Smart Router: An attacker-controlled TCP option causes an out-of-bounds write when using the TCP proxy feature
Medium 5.3
Published
Updated
Check this codebase for CVE-2026-103391 and fix it if it is affected.
What it is: CVE-2026-103391 is a medium-severity vulnerability in Juniper Networks Session Smart Router, published on 28 Oct 2026.
Exploitation: There is no known exploitation of CVE-2026-103391 in the wild and no public exploit code.
Affected product: Juniper Networks Session Smart Router. 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-2026-103391/ (Markdown: https://insights.sbomify.com/CVE-2026-103391/index.md)
- Exploited in the wild
- Not known
- Fix
- None listed
What is CVE-2026-103391?
CVE-2026-103391 is a medium-severity vulnerability in Juniper Networks Session Smart Router, published on 28 Oct 2026.
Official description
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.
Weakness: CWE-787
Which versions are affected by CVE-2026-103391?
How do I fix CVE-2026-103391?
No fix has been published for CVE-2026-103391 yet. Limit exposure of the affected software until one is available.
Is CVE-2026-103391 being exploited?
There is no known exploitation of CVE-2026-103391 in the wild and no public exploit code.
Sources
Also known as GHSA-mg4c-h4g5-47fv.