PAN-OS: Threat signatures are evaded by specifically crafted packets

published 2020-11-12 5y ago modified 2026-06-17 4mo ago also EUVD-2020-12789

cvss: 5.3; version 3.1, CNA
cisa kev: Not listed; not in CISA's catalog
epss: 1.3%; EPSS 1.3% chance of exploitation in 30 days, percentile 71%
public exploits: 0; none known

A vulnerability exists in the Palo Alto Network PAN-OS signature-based threat detection engine that allows an attacker to communicate with devices in the network in a way that is not analyzed for threats by sending data through specifically crafted TCP packets. This technique evades signature-based threat detection. This issue impacts: PAN-OS 8.1 versions earlier than 8.1.17; PAN-OS 9.0 versions earlier than 9.0.11; PAN-OS 9.1 versions earlier than 9.1.5; All versions of PAN-OS 7.1 and PAN-OS 8.0.

Patch / fix

fixed in 1

Palo Alto Networks PAN-OS 8.1.17, 9.0.11, 9.1.5

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Exploit prediction

1.34% chance of exploitation in the next 30 days, higher than 71% of all scored CVEs (FIRST EPSS, 2026-11-09).

CVSS scores

assigned by	version	score	vector
CNA	3.1	5.3	CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:N
NVD	3.1	5.3	CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:N
NVD	2.0	5.0	AV:N/AC:L/Au:N/C:N/I:P/A:N

Affected products

Palo Alto Networks PAN-OS

Classification

Weakness

CWE-754 Improper Check for Unusual or Exceptional Conditions

Technology feeds

Palo Alto PAN-OS rss critical rss

References

security.paloaltonetworks.com /CVE-2020-1999
vendor-advisory

Sources

CVE List CVE-2020-1999
NVD CVE-2020-1999

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