Junos OS (SRX firewalls)
CVE-2026-101955: SRX Series: Malformed DNS packet causes service disruption when UTM Anti-Spam SBL is used
A Stack-based Buffer Overflow vulnerability in the UTM Anti-Spam SBL of Juniper Networks Junos OS on SRX series allows an unauthenticated remote attacker to cause arbitrary code execution or a denial of service via a injected malformed DNS packet when Anti-Spam SBL inspection is enabled.
Published Juniper Networks advisory JSA112186
Automatic summary from the vendor's CVE record. We haven't written a full analysis of this vulnerability yet.
Affected and fixed versions
| Product / branch | Fixed in |
|---|---|
| Junos OS 0 | 23.2R2-S7.7 or later |
| Junos OS 23.4 | 23.4R2-S8.13 or later |
| Junos OS 24.2 | 24.2R2-S5.5 or later |
| Junos OS 24.4 | 24.4R2-S5 or later |
| Junos OS 25.2 | 25.2R2-S2 or later |
| Junos OS 25.4 | 25.4R1-S3 or later |
| Junos OS 26.2 | 26.2R1-S2 or later |
Always confirm against the vendor advisory, which lists every fixed hotfix.
In short
A stack-based buffer overflow in the UTM Anti-Spam SBL feature of Junos OS on SRX firewalls allows an unauthenticated remote attacker to inject a malformed DNS packet. This flaw enables the attacker to achieve arbitrary code execution or cause a denial of service without requiring login credentials or user interaction, provided that Anti-Spam SBL inspection is enabled.
Written by a language model from the vendor's description. Versions, fixes and exploitation status on this page come straight from the vendor and CISA.
The vendor's description
A Stack-based Buffer Overflow vulnerability in the UTM Anti-Spam SBL of Juniper Networks Junos OS on SRX series allows an unauthenticated remote attacker to cause arbitrary code execution or a denial of service via a injected malformed DNS packet when Anti-Spam SBL inspection is enabled.
Am I affected?
[ security utm default-configuration anti-spam type sbl ]
Workarounds
There are no known workarounds for this issue.
Exploitation
Juniper SIRT is not aware of any malicious exploitation of this vulnerability.
Sources
KEV status, EPSS score and vendor data refreshed automatically, last on 19 Oct 2026.