CVE-2021-3031

Adjacent memory disclosure via uncleared Ethernet padding

Published Jan 13, 2021 · Updated Sep 16, 2024

Information exposure in affected PAN-OS 8.1, 9.0, and 9.1 releases allows remote attackers on the same subnet to read firewall memory. Ethernet frame construction leaves padding bytes uncleared, so frames include stale firewall-memory contents instead of zero-filled padding. Exposure requires access to the same Ethernet subnet and is limited to small, random memory fragments; affected releases are 8.1 before 8.1.18, 9.0 before 9.0.12, and 9.1 before 9.1.5.

CVSS severity4.3
Medium
EPSS probability0.54%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Information exposure in affected PAN-OS 8.1, 9.0, and 9.1 releases allows remote attackers on the same subnet to read firewall memory. Ethernet frame construction leaves padding bytes uncleared, so frames include stale firewall-memory contents instead of zero-filled padding. Exposure requires access to the same Ethernet subnet and is limited to small, random memory fragments; affected releases are 8.1 before 8.1.18, 9.0 before 9.0.12, and 9.1 before 9.1.5.

The record

CVE
CVE-2021-3031
Published
Jan 13, 2021
Updated
Sep 16, 2024
Vendor
Palo Alto Networks
Product
PAN-OS
Classifications
CWE-200, T1040
Attack vector
adjacent
Privileges
unauthenticated

Timeline

How it unfolded

  1. Jan 13, 2021CVE publishedPublication date reported by the CVE source.
  2. Sep 16, 2024Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

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Is a vulnerable build present?

Compare these published version ranges with your installed build and any vendor patches.

  1. Affected versionversion=8.1 <8.1.18
  2. Affected versionversion=9.0 <9.0.12
  3. Affected versionversion=9.1 <9.1.5

What conditions does exploitation require?

Attack vectoradjacent
Required privilegesunauthenticated

What is affected?

Palo Alto Networks · PAN-OSversion=8.1 <8.1.18; version=9.0 <9.0.12; version=9.1 <9.1.5

Published CVSS scores

4.3Palo Alto NetworksCVSS:3.1/AV:A/AC:L/PR:N/UI:N/S:U/C:L/I:N/A:N

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

Daily unique IPsNo honeypot observations are available for this CVE in the selected window.

No observations available

Sep 10, 2026Sep 16, 2026
Latest reporting daySep 16, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectoradjacent
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-200Information Exposure
T1040Network Sniffing

Public exploit references

No public exploit references are available in this record.

Labels summarize the accepted research assessment. They do not indicate a test against your environment.

Technologies

Your stack

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Your stack

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