CVE-2021-3594Public exploit

Host-memory disclosure via unchecked UDP header length

Published Jun 15, 2021 · Updated Aug 3, 2024

Information disclosure in libslirp before 4.6.0 allows guest OS users to read host memory by sending a truncated UDP packet. The udp_input() function derives a UDP-header pointer from the packet buffer and reads its length without first verifying that the mbuf contains a full udphdr structure. Control of a guest using libslirp user-mode networking is required; the bounded consequence is an out-of-bounds read and indirect host-memory disclosure to that guest.

CVSS severity3.8
Low
EPSS probability0.33%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Information disclosure in libslirp before 4.6.0 allows guest OS users to read host memory by sending a truncated UDP packet. The udp_input() function derives a UDP-header pointer from the packet buffer and reads its length without first verifying that the mbuf contains a full udphdr structure. Control of a guest using libslirp user-mode networking is required; the bounded consequence is an out-of-bounds read and indirect host-memory disclosure to that guest.

The record

CVE
CVE-2021-3594
Published
Jun 15, 2021
Updated
Aug 3, 2024
Vendor
Libslirp Project
Product
libslirp
Classifications
CWE-824, T1005
Attack vector
local
Privileges
authenticated

Timeline

How it unfolded

  1. Jun 15, 2021CVE publishedPublication date reported by the CVE source.
  2. Aug 3, 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=libslirp 4.6.0

What conditions does exploitation require?

Attack vectorlocal
Required privilegesauthenticated

What is affected?

Libslirp Project · libslirpversion=libslirp 4.6.0

Published CVSS scores

3.8NIST NVDCVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:C/C:L/I:N/A:N
2.1NIST NVDAV:L/AC:L/Au:N/C:P/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.

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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 exploitPublished

Weakness, pattern, technique

CWE-824Access of Uninitialized Pointer
T1005Data from Local System

Public exploit references

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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