CVE-2019-20788Network attack vector

Heap corruption via undersized cursor pixel buffer

Published Apr 23, 2020 · Updated Aug 5, 2024

Heap buffer overflow in LibVNCServer through 0.9.12 allows remote attackers to corrupt a connecting client's memory via crafted cursor data. HandleCursorShape multiplies server-controlled width, height, and pixel-size values using 32-bit arithmetic, underallocating rcSource before writes use the original dimensions. The client must connect to an attacker-controlled VNC server; successful corruption can crash the client or execute code under favorable memory conditions.

CVSS severity9.8
Critical
EPSS probability2.50%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Heap buffer overflow in LibVNCServer through 0.9.12 allows remote attackers to corrupt a connecting client's memory via crafted cursor data. HandleCursorShape multiplies server-controlled width, height, and pixel-size values using 32-bit arithmetic, underallocating rcSource before writes use the original dimensions. The client must connect to an attacker-controlled VNC server; successful corruption can crash the client or execute code under favorable memory conditions.

The record

CVE
CVE-2019-20788
Published
Apr 23, 2020
Updated
Aug 5, 2024
Vendor
Unknown vendor
Product
Unknown product
Classifications
CWE-787, CWE-190, T1203
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Apr 23, 2020CVE publishedPublication date reported by the CVE source.
  2. Aug 5, 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?

Affected buildAffected product and version details are unavailable.

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

Affected products and versions are unavailable in this record.

Published CVSS scores

7.5NIST NVDAV:N/AC:L/Au:N/C:P/I:P/A:P
9.8NIST NVDCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
9.8Canonical UbuntuCVSS:3.1/AV:N/AC:L/PR:N/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 9, 2026Sep 15, 2026
Latest reporting daySep 15, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-787Out-of-bounds Write
CWE-190Integer Overflow or Wraparound
T1203Exploitation for Client Execution

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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