high CVSS 7.8 EPSS <0.1%

CVE-2026-33793·Python vulnerability

An Execution with Unnecessary Privileges vulnerability in the User Interface (UI) of Juniper Networks Junos OS and Junos OS Evolved allows a local, low-privileged attacker to gain root privileges, thus compromising the system. When a configuration that allows unsigned Python op scripts is present on the device, a non-root user is able to execute malicious op scripts as a root-equivalent user, leading to privilege escalation.  This issue affects Junos OS:  * All versions before 22.4R3-S7,  * from 23.2 before 23.2R2-S4,  * from 23.4 before 23.4R2-S6, * from 24.2 before 24.2R1-S2, 24.2R2,  * from 24.4 before 24.4R1-S2, 24.4R2;  Junos OS Evolved:  * All versions before 22.4R3-S7-EVO,  * from 23.2 before 23.2R2-S4-EVO,  * from 23.4 before 23.4R2-S6-EVO, * from 24.2 before 24.2R2-EVO,  * from 24.4 before 24.4R1-S1-EVO, 24.4R2-EVO.

Severity
high
Software
Python
Fixed in
22.4
Published

How likely is exploitation

FIRST's Exploit Prediction Scoring System puts the probability of this CVE being exploited in the next 30 days at <0.1% — in the bottom 1% of all published CVEs. EPSS is an independent forecast of exploitation, not a severity rating: it says nothing about how much damage a successful attack does, which is what a CVSS score measures.

Read the two together. CVE-2026-33793 scores 7.8 on CVSS, so a successful attack would be serious — but at <0.1%, almost nobody is currently attempting it. That is a different situation from a flaw under mass exploitation, and it is usually the difference between patching on your next maintenance window and patching tonight.

Affected versions

Until: 22.4

Fixed in: 22.4

How to fix this CVE

Upgrade Python to version 22.4 or later to patch this privilege escalation vulnerability. Users running Juniper Junos OS or Junos OS Evolved should immediately apply the corresponding security updates for their release branch. If unsigned Python op scripts are not required in your environment, disable this feature in your device configuration to reduce exposure.

sudo dnf update python3

Defensia detects this vulnerability

How to check if you are affected

  1. Step 1: Check installed Python version with `python3 --version` and cross-reference against your Junos OS release notes to identify if you are below the patched version (22.4R3-S7 or later for standard releases)
  2. Step 2: On Juniper devices, verify if unsigned op scripts are enabled by examining your configuration with `show configuration system scripts op` — if this feature is active, your system is at risk
  3. Step 3: Search syslog and audit logs for unexpected op script execution patterns: `grep -i 'op script' /var/log/syslog /var/log/audit/audit.log` and look for entries from non-root users executing scripts with elevated privileges
  4. Step 4: Confirm the patch was applied by running `python3 --version` again and verifying the output matches or exceeds version 22.4, or check Junos device version with `show version` to confirm it reports the patched software version

FAQ

What is CVE-2026-33793?

CVE-2026-33793 is a privilege escalation vulnerability in Juniper Junos OS and Junos OS Evolved that allows local, low-privileged users to execute arbitrary Python op scripts with root-equivalent permissions when unsigned scripts are permitted in the device configuration.

Is CVE-2026-33793 being actively exploited?

No, according to CISA's Known Exploited Vulnerabilities catalog, CVE-2026-33793 is not currently being actively exploited in the wild, and no public exploit code is available.

What versions of Python are affected by CVE-2026-33793?

All Python versions bundled in Junos OS versions before 22.4R3-S7 (standard track) and before 22.4R3-S7-EVO (evolved track) are affected; later releases including 23.2R2-S4, 23.4R2-S6, 24.2R1-S2, and 24.4R1-S2 branches have received patches.

How do I check if my server is vulnerable to CVE-2026-33793?

Run `show version` on your Juniper device and compare the output against the affected version ranges; if your version is older than the patched version for your release branch, you are vulnerable. Additionally, verify unsigned op scripts are not enabled with `show configuration system scripts op`.

Does Defensia detect CVE-2026-33793?

Yes — Defensia's CVE advisory scanner compares installed package versions against the NVD database. If Python is installed on a monitored Juniper Junos OS device, CVE-2026-33793 will appear in your dashboard with remediation steps.

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References

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