Junos OS: Integer Underflow in kernel causes denial of service
Summary
An Integer Underflow in the kernel of Juniper Networks Junos OS allows an unauthenticated, network-based attacker to crash the kernel and cause a denial of service. The flaw is only reachable when the Extended Echo feature is configured. Juniper's CNA rates the issue with CVSS 4.0 score 9.3, but the described impact is limited to availability, so the vector should be verified against the advisory.
Affected
- Junos OS 0 to < 23.2R2-S7.7
- Junos OS 23.4 to < 23.4R2-S8.13
- Junos OS 24.2 to < 24.2R2-S5.5
- Junos OS 24.4 to < 24.4R2-S5
- Junos OS 25.2 to < 25.2R2-S2
- Junos OS 25.4 to < 25.4R1-S3
- Junos OS 26.2 to < 26.2R1-S2
- Only with system extended-echo configured (default: unaffected)
Fixed in
- Junos OS 23.2R2-S7.7, 23.4R2-S8.13, 24.2R2-S5.5, 24.4R2-S5, 25.2R2-S2, 25.4R1-S3, 25.4R2, 26.2R1-S2, 26.2R2, 26.4R1 and all subsequent releases
- Releases 23.2, 23.4 and 24.2 have respins; previously published builds were rebuilt.
Workaround
- No workaround is listed by the vendor.
- Secondary sources recommend disabling Extended Echo if patching cannot happen immediately; verify this against JSA112188 first.
Exploitation
- Juniper SIRT is not aware of any malicious exploitation.
- A third-party mirror lists the CVE as not in KEV; no public proof-of-concept found.
- CISA SSVC: automatable yes, technical impact partial.
Our recommendation
- Check whether any Junos device has system extended-echo configured.
- Patch affected devices to a fixed release from JSA112188.
- Restrict access to management and transit interfaces to trusted networks until patched.
- Monitor for unexpected reboots or loss of connectivity on routers and firewalls.
Public exploits
PoC-in-GitHub, Metasploit and Exploit-DB list nothing for this CVE.
Research sources
- Juniper Security Advisory JSA112188 supportportal.juniper.net
- Vulners VulnRichment CVE-2026-101980 vulners.com
- Strix CVE-2026-101980 www.strix.ai
- OpenCVE CVE-2026-101980 app.opencve.io
- NetSecObserver article on Extended Echo netsecobserver.com
- CloudSecAlert article on Junos OS Extended Echo cloudsecalert.com
Researched and written up in English and German by an AI (Claude by Anthropic) based on NVD, CISA, EPSS and the sources listed. The vendor information is authoritative. Researched on 31 Oct 2026, 01:57.
Original description (NVD)
An Integer Underflow vulnerability in the kernel of Juniper Networks Junos OS with Extended Echo configured allows an unauthenticated, network-based attacker to cause a denial of service by a kernel crash.
NVD references (1)
Sources
The tracker combines official, freely usable data sources – updated continuously:
- NVD (NIST) – CVEs, rating (CVSS), affected products
- CISA KEV – vulnerabilities confirmed by CISA as actively exploited
- CISA Vulnrichment – CISA assessment (SSVC) in the official CVE record
- FIRST EPSS – probability of exploitation
- Microsoft MSRC – Patch Tuesday: vulnerabilities, severity, updates
- PoC-in-GitHub – public proof-of-concept repositories
- Metasploit (Rapid7) – modules of the Metasploit Framework
- Exploit-DB (OffSec) – archive of public exploits (links only)
- Patch days: official vendor pages (linked per vendor) (Vendor patch days)
This product uses data from the NVD API but is not endorsed or certified by the NVD. EPSS data © FIRST.org.
Affected? We can help.
We check whether your systems are affected, install updates and close the gap – continuously with the System Health Checker if you wish.