Juniper Junos OS Evolved: Denial of service via SNMP firewall counter query
Summary
A reachable assertion in the fwstatsd daemon of Junos OS Evolved can be triggered by an SNMP query against the firewall-counter MIB. An attacker with network access to SNMP can crash the process and cause a denial of service. The issue only occurs when at least one firewall counter is configured. Confidentiality and integrity are not affected.
Affected
- Junos OS Evolved 0 to < 23.2R2-S7.7-EVO
- Junos OS Evolved 23.4 to < 23.4R2-S8.11-EVO
- Junos OS Evolved 24.2 to < 24.2R2-S5.6-EVO
- Junos OS Evolved 24.4 to < 24.4R2-S5-EVO
- Junos OS Evolved 25.2 to < 25.2R2-S2-EVO
- Junos OS Evolved 25.4 to < 25.4R1-S3-EVO
- Junos OS Evolved 26.2 to < 26.2R1-S2-EVO
- Junos OS Evolved 23.4X100 (fixed version unknown)
- Junos OS Evolved 25.2X100 to < 25.2X100-D35-EVO
- Junos OS Evolved 25.4X300 to < 25.4X300-D40-EVO
Version ranges are taken from the CVE record and aggregators and must be checked against JSA112250.
Fixed in
- 23.2R2-S7.7-EVO
- 23.4R2-S8.11-EVO
- 24.2R2-S5.6-EVO
- 24.4R2-S5-EVO
- 25.2R2-S2-EVO
- 25.2X100-D35-EVO
- 25.4R1-S3-EVO
- 25.4R2-EVO
- 25.4X300-D40-EVO
- 26.2R1-S2-EVO
- 26.2R2-EVO
- 26.4R1-EVO
- All subsequent releases
For 23.2-EVO, 23.4-EVO and 24.2-EVO, respins have been published and previously released images were rebuilt.
Workaround
Unknown. Juniper lists no known workarounds. Restricting SNMP access to management networks reduces exposure but is not a vendor workaround.
Exploitation
- Juniper SIRT is not aware of malicious exploitation.
- No public proof of concept or CISA KEV entry was found in the research notes; this is not fully verified.
- CISA SSVC: exploitation none, automatable yes, technical impact partial.
Our recommendation
- Check whether Junos OS Evolved devices are in use; if not, no action is needed.
- Verify whether firewall counters and SNMP queries against them are configured.
- Update to a fixed release listed in JSA112250.
- Limit SNMP access to dedicated management networks and monitor for fwstatsd crashes.
- Re-check the CVSS vector: the description says authenticated access is required, while the vector shows no privileges required.
Public exploits
PoC-in-GitHub, Metasploit and Exploit-DB list nothing for this CVE.
Research sources
- Juniper advisory JSA112250 supportportal.juniper.net
- CVE-2026-102023 on threatint.com cve.threatint.com
- CVE-2026-102023 on strix.ai www.strix.ai
- Positive Technologies PT-2026-113864 vulners.com
- Junos OS background (Wikipedia) en.wikipedia.org
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 1 Nov 2026, 03:21.
Original description (NVD)
A Reachable Assertion vulnerability in fwstatsd of Juniper Networks Junos OS Evolved allows an authenticated network attacker to cause a denial of service via an SNMP firewall-counter MIB query when at least one firewall counter is configured.
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.
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