CVE-2026-21917
Junos OS: SRX Series: Specifically malformed SSL packet causes FPC crash
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.
INFO
Published Date :
Jan. 15, 2026, 9:16 p.m.
Last Modified :
Jan. 15, 2026, 9:16 p.m.
Remotely Exploit :
Yes !
Source :
[email protected]
Affected Products
The following products are affected by CVE-2026-21917
vulnerability.
Even if cvefeed.io is aware of the exact versions of the
products
that
are
affected, the information is not represented in the table below.
No affected product recoded yet
CVSS Scores
| Score | Version | Severity | Vector | Exploitability Score | Impact Score | Source |
|---|---|---|---|---|---|---|
| CVSS 3.1 | HIGH | 8cbe9d5a-a066-4c94-8978-4b15efeae968 | ||||
| CVSS 3.1 | HIGH | [email protected] | ||||
| CVSS 4.0 | HIGH | 8cbe9d5a-a066-4c94-8978-4b15efeae968 | ||||
| CVSS 4.0 | HIGH | [email protected] |
Solution
- Update Junos OS to a fixed version.
- Apply security patches for SRX Series devices.
- Monitor FPC status after updates.
- Review UTM Web-Filtering configurations.
References to Advisories, Solutions, and Tools
Here, you will find a curated list of external links that provide in-depth
information, practical solutions, and valuable tools related to
CVE-2026-21917.
| URL | Resource |
|---|---|
| https://kb.juniper.net/JSA105996 | |
| https://supportportal.juniper.net/JSA105996 |
CWE - Common Weakness Enumeration
While CVE identifies
specific instances of vulnerabilities, CWE categorizes the common flaws or
weaknesses that can lead to vulnerabilities. CVE-2026-21917 is
associated with the following CWEs:
Common Attack Pattern Enumeration and Classification (CAPEC)
Common Attack Pattern Enumeration and Classification
(CAPEC)
stores attack patterns, which are descriptions of the common attributes and
approaches employed by adversaries to exploit the CVE-2026-21917
weaknesses.
We scan GitHub repositories to detect new proof-of-concept exploits. Following list is a collection of public exploits and proof-of-concepts, which have been published on GitHub (sorted by the most recently updated).
Results are limited to the first 15 repositories due to potential performance issues.
The following list is the news that have been mention
CVE-2026-21917 vulnerability anywhere in the article.
The following table lists the changes that have been made to the
CVE-2026-21917 vulnerability over time.
Vulnerability history details can be useful for understanding the evolution of a vulnerability, and for identifying the most recent changes that may impact the vulnerability's severity, exploitability, or other characteristics.
-
New CVE Received by [email protected]
Jan. 15, 2026
Action Type Old Value New Value Added 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. Added CVSS V4.0 AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:L/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:Y/R:A/V:X/RE:M/U:X Added CVSS V3.1 AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H Added CWE CWE-1286 Added Reference https://kb.juniper.net/JSA105996 Added Reference https://supportportal.juniper.net/JSA105996