Home/CVE/An Improper Validation of Syntactic Correctness of Input vulnerability in the Web-Filtering module of Juniper Networks J
CVE

CVE-2026-21917

An Improper Validation of Syntactic Correctness of Input vulnerability in the Web-Filtering module of Juniper Networks J

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.

HIGH · CVSS 7.5 EPSS 0.00042
Schedule remediation
  • SSVC automatable: yes - attacks can be scripted at scale
  • CVSS base score ≥ 7.0
Sigma rules0 YARA rules0
⬡

Weakness Classification

CWE-1286Improper Validation of Syntactic Correctness of Input
▤

Affected Products & Versions

1
juniper junosall versions
▣

Scoring & Timeline

7.5
HIGH · CVSS v3.1 · sirt@juniper.net
View on NVD
Attack Vector
Network Adjacent Local Physical
Attack Complexity
Low High
Privileges Required
None Low High
User Interaction
None Required
Scope
Unchanged Changed
Confidentiality
None Low High
Integrity
None Low High
Availability
None Low High
Published to NVD15 Jan 2026 · 09:16 PM
CVSS VectorCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
SSVC triage · cisa-vulnrichment
Exploitation
none
Automatable
yes
Technical impact
partial
SSVC asks the questions that actually drive patch urgency: is it being exploited, can attacks be automated, and how total is the impact.
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References & Sources

2
Source URLs (vendor pages, mailing lists, write-ups). Exploit/PoC links are in their own section above to avoid duplication.
https://kb.juniper.net/JSA105996Vendor Advisory
https://supportportal.juniper.net/JSA105996Vendor Advisory
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