# CVE-2026-101991: Junos OS and Junos OS Evolved: A BGP-LS peer causes heap data disclosure when traffic-engineering routing is enabled

> A configured BGP-LS peer can disclose heap data by sending a malformed UPDATE when traffic-engineering routing is enabled.

- **Severity:** Medium 5.3 (`CVSS:4.0/AV:A/AC:L/AT:N/PR:N/UI:N/VC:L/VI:N/VA:N/SC:N/SI:N/SA:N`)
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Local or same network only
- **Victim action needed:** Not needed
- **Fix available:** No
- **Published:** 14 Oct 2026
- **Updated:** 14 Oct 2026
- **Also known as:** GHSA-7hq3-vcv5-qgqv

## What is CVE-2026-101991?

CVE-2026-101991 is a medium-severity vulnerability in Juniper Networks Junos OS, published on 14 Oct 2026. It can only be exploited from the same machine or local network, with no action from the victim.

### Official description

An Improper Handling of Length Parameter Inconsistency vulnerability in the routing protocol daemon (rpd) of Juniper Networks Junos OS and Junos OS Evolved allows a configured BGP-LS peer to cause heap data disclosure via a malformed UPDATE sent over a session with the traffic-engineering address family enabled.

Weakness: CWE-130 (Improper Handling of Length Parameter Inconsistency)

## Which versions are affected by CVE-2026-101991?


## How do I fix CVE-2026-101991?

No fix has been published for CVE-2026-101991 yet. Limit exposure of the affected software until one is available.

## Is CVE-2026-101991 being exploited?

There is no known exploitation of CVE-2026-101991 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-101991 and fix it if it is affected.

What it is: CVE-2026-101991 is a medium-severity vulnerability in Juniper Networks Junos OS, published on 14 Oct 2026. It can only be exploited from the same machine or local network, with no action from the victim.
Exploitation: There is no known exploitation of CVE-2026-101991 in the wild and no public exploit code.

Affected product: Juniper Networks Junos OS. 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-2026-101991/ (Markdown: https://insights.sbomify.com/CVE-2026-101991/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-101991
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-101991
- OSV: https://osv.dev/vulnerability/CVE-2026-101991

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-101991/
Summaries are generated and may contain mistakes; the official description above is the record.