CVE-2026-21917
- CVSS Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
- Published: 2026-01-15T21:16:07.877
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.
Related CVE by CWE
No related CWE found.
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How to fix CVE-2026-21917
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 […]
Exploit Difficulty: EASY
⏱️ Time to exploit: < 1 hour
🛠️ Required skills: Basic web security knowledge
💰 Public exploits: Likely available
How to Fix:
- Check if you're running the affected product
- Update to the latest patched version
- If patching is not immediately possible: restrict network exposure, apply least-privilege access
- Test the fix in a staging environment first
- Review logs for signs of exploitation
- Monitor for IOCs (Indicators of Compromise)
- Enable automatic security updates
- Set up vulnerability monitoring
- Review and harden security configurations
Exploit Difficulty Assessment
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No vendor/product data available.