CVE-2020-3257

Privileged code execution via unchecked signaling TLVs

Published Jun 3, 2020 · Updated Nov 15, 2024

Buffer overflow in the Cisco IOS inter-VM channel allows local users on affected industrial routers to execute code with high privileges. Incorrect bounds checks on TLV fields let crafted signaling packets overflow the process that manages TCP communication between the Guest OS and IOS VMs. Exploitation requires low-privileged device credentials and Guest OS connectivity, and successful code runs in the privileged IOS VM.

CVSS severity7.8
High
EPSS probability0.70%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Buffer overflow in the Cisco IOS inter-VM channel allows local users on affected industrial routers to execute code with high privileges. Incorrect bounds checks on TLV fields let crafted signaling packets overflow the process that manages TCP communication between the Guest OS and IOS VMs. Exploitation requires low-privileged device credentials and Guest OS connectivity, and successful code runs in the privileged IOS VM.

The record

CVE
CVE-2020-3257
Published
Jun 3, 2020
Updated
Nov 15, 2024
Vendor
ClamAV
Product
Cisco IOS
Classifications
CWE-119, CWE-20, T1068
Attack vector
local
Privileges
authenticated

Timeline

How it unfolded

  1. Jun 3, 2020CVE publishedPublication date reported by the CVE source.
  2. Nov 15, 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=n/a

What conditions does exploitation require?

Attack vectorlocal
Required privilegesauthenticated

What is affected?

ClamAV · Cisco IOSversion=n/a

Published CVSS scores

4.8NIST National Vulnerability DatabaseAV:A/AC:L/Au:N/C:N/I:P/A:P
8.1NIST National Vulnerability DatabaseCVSS:3.1/AV:A/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:H
7.8Cisco Systems, Inc.CVSS:3.0/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H

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)
Vectorlocal
Privilegesauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-119Improper Restriction of Operations within the Bounds of a Memory Buffer
CWE-20Improper Input Validation
T1068Exploitation for Privilege Escalation

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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