High severity · published Jan 15, 2026
CVE-2026-21917
Junos OS: SRX Series: Specifically malformed SSL packet causes FPC crash
7.5
CVSS
0.4%
EPSS
No
On KEV
Description
An Improper Validation of Syntactic Correctness of Input vulnerability in the Web-Filtering module of Juniper Networks Junos OS on SRX Series allows an unauthenticated, network-based attacker to cause a Denial-of-Service (DoS). If an SRX device configured for UTM Web-Filtering receives a specifically malformed SSL packet, this will cause an FPC crash and restart. This issue affects Junos OS on SRX Series: * 23.2 versions from 23.2R2-S2 before 23.2R2-S5,  * 23.4 versions from 23.4R2-S1 before 23.4R2-S5, * 24.2 versions before 24.2R2-S2, * 24.4 versions before 24.4R1-S3, 24.4R2. Earlier versions of Junos are also affected, but no fix is available.
CVSS vector
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
Attack vector
Network
Complexity
Low
Privileges
None
User interaction
None
Confidentiality
None
Integrity
None
Availability
High
Scope
Unchanged
Exploitation
Is it being used?
Exploit prediction (EPSS)0.4% · higher than 35% of CVEs
Exploited in the wildNo evidence yet
CISA KEVNot listed
Ransomware campaign useNot known
Affected products
Which versions
JO
Junos OS · Juniper
23.2R2-S2 before 23.2R2-S5; 23.4R2-S1 before 23.4R2-S5; 24.2 before 24.2R2-S2; 24.4 before 24.4R1-S3, 24.4R2 · source: vendor, NVD
Affected product
JO
Junos OS
Juniper
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