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Libslirp CVE-2021-3595

LOW
Access of Uninitialized Pointer (CWE-824)
2021-06-15 secalert@redhat.com
3.8
CVSS 3.1 · NVD
View

Vulnerability Assessment

Weakness
CWE
ASVS 5.0
V15 - Secure Coding and Architecture Uninitialized pointer prevention
MITRE ATT&CK

1 technique across 1 tactic: Execution

The technique list with ATT&CK links and the kill-chain view is part of the Basic plan and up.

Impact

CVSS score of 3.8 (LOW). Attack characteristics: local attack vector, low complexity, low privileges required, no user interaction not required.

Exploit ScenarioDerived

Successful exploitation could compromise the low-severity affected system.

Monitor Track and reassess. Why: LOW severity (CVSS 0.1-3.9).
Patch available 0.3% exploitation probability (EPSS)

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AnalysisAI

An invalid pointer initialization issue was found in the SLiRP networking implementation of QEMU. Rated low severity (CVSS 3.8), this vulnerability is low attack complexity.

RemediationAI

A vendor patch is available. Apply the latest security update as soon as possible. Apply vendor patches when available. Implement network segmentation and monitoring as interim mitigations.

Affects your stack

Find out whether the stacks and servers you run are on an affected version.

Checking this CVE against your own stacks and servers is part of the Basic plan and up.

Technical ContextAI · show details

This vulnerability is classified under CWE-824. An invalid pointer initialization issue was found in the SLiRP networking implementation of QEMU. The flaw exists in the tftp_input() function and could occur while processing a udp packet that is smaller than the size of the 'tftp_t' structure. This issue may lead to out-of-bounds read access or indirect host memory disclosure to the guest. The highest threat from this vulnerability is to data confidentiality. This flaw affects libslirp versions prior to 4.6.0. Affected products include: Libslirp Project Libslirp, Redhat Enterprise Linux, Debian Debian Linux, Fedoraproject Fedora. Version information: prior to 4.6.0..

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Severity by source

NVD PRIMARY 3.8 LOW
AV:L/AC:L/PR:L/UI:N/S:C/C:L/I:N/A:N

Primary rating from NVD · only source for this CVE.

CVSS VectorNVD

Attack Vector
Local
Attack Complexity
Low
Privileges Required
Low
User Interaction
None
Scope
Changed
Confidentiality
Low
Integrity
None
Availability
None

DescriptionNVD

An invalid pointer initialization issue was found in the SLiRP networking implementation of QEMU. The flaw exists in the tftp_input() function and could occur while processing a udp packet that is smaller than the size of the 'tftp_t' structure. This issue may lead to out-of-bounds read access or indirect host memory disclosure to the guest. The highest threat from this vulnerability is to data confidentiality. This flaw affects libslirp versions prior to 4.6.0.

Threat Intelligence Overview

EPSS Score
0.3%
Top 75% exploitable
Data Quality
2 sources
Confidence: Low

How this decision was reached

The engine reads each signal below and applies a fixed list of rules from top to bottom. The first rule that matches sets the recommended action – like a statement, every line is shown.

SignalValue
Severity LOW
CISA KEV No
Public POC No
EPSS 0.3%
Patch available Yes
Active threat No
Deciding rule
LOW severity (CVSS 0.1-3.9)
What every action level means
Emergency Immediate action required. Criteria: CRITICAL + in CISA KEV (actively exploited) without patch, OR CRITICAL + EPSS > 30% without patch, OR CRITICAL + active threat signals without patch.
Act Now Prioritize within 24-48h. Criteria: in KEV with patch available, OR CRITICAL + public POC, OR HIGH + EPSS > 10%, OR CRITICAL + active threat, OR any CRITICAL severity.
This Week Schedule remediation this week. Criteria: HIGH severity (CVSS 7.0-8.9). Patch within normal change window.
This Month Plan within 30 days. Criteria: MEDIUM severity (CVSS 4.0-6.9), lower exploitation probability. Include in regular patch cycle.
Monitor Track and reassess. Criteria: LOW severity (CVSS 0.1-3.9), minimal exploitation risk. No immediate action needed.

SSVC AssessmentENISA

SSVC Decision· derived
Defer
Exploitation· derived
None
System Exposure· derived
Small
Automatable· derived
No
Human Impact· derived
Low

Priority Score

19
Low Medium High Critical
KEV: 0
EPSS: 0
CVSS: +19
PoC: 0
Weaponized: 0
Threat intel: 0
Gov advisory: 0

Attack Technique

A buffer overflow occurs when a program writes more data to a memory buffer than it was allocated to hold, causing the excess data to spill into adjacent memory regions.

Memory corruption occurs when a program writes data beyond the boundaries of allocated memory regions or accesses memory in unintended ways, violating the integrity of the process's address space.

Affected Products (CPE)NVD

cpe:2.3:a:libslirp_project:libslirp:*:*:*:*:*:*:*:*
cpe:2.3:o:redhat:enterprise_linux:8.0:*:*:*:*:*:*:*
cpe:2.3:o:redhat:enterprise_linux:8.0:*:*:*:advanced_virtualization:*:*:*
cpe:2.3:o:debian:debian_linux:9.0:*:*:*:*:*:*:*
cpe:2.3:o:fedoraproject:fedora:33:*:*:*:*:*:*:*
cpe:2.3:o:fedoraproject:fedora:34:*:*:*:*:*:*:*
CVE-2020-1983 MEDIUM POC
6.5 Apr 22

A use after free vulnerability in ip_reass() in ip_input.c of libslirp 4.2.0 and prior releases allows crafted packets t

CVE-2019-14378 HIGH POC
8.8 Jul 29

ip_reass in ip_input.c in libslirp 4.0.0 has a heap-based buffer overflow via a large packet because it mishandles a cas

CVE-2020-29130 MEDIUM POC
4.3 Nov 26

slirp.c in libslirp through 4.3.1 has a buffer over-read because it tries to read a certain amount of header data even i

CVE-2020-7211 HIGH
7.5 Jan 21

tftp.c in libslirp 4.1.0, as used in QEMU 4.2.0, does not prevent ..\ directory traversal on Windows. Rated high severit

CVE-2019-15890 HIGH
7.5 Sep 06

libslirp 4.0.0, as used in QEMU 4.1.0, has a use-after-free in ip_reass in ip_input.c. Rated high severity (CVSS 7.5), t

CVE-2026-9539 MEDIUM
6.5 Jun 24

Out-of-bounds heap read and integer underflow in libslirp's TCP urgent data handler (sosendoob) exposes gigabytes of hos

CVE-2020-10756 MEDIUM
6.5 Jul 09

An out-of-bounds read vulnerability was found in the SLiRP networking implementation of the QEMU emulator. Rated medium

CVE-2020-8608 MEDIUM
5.6 Feb 06

In libslirp 4.1.0, as used in QEMU 4.2.0, tcp_subr.c misuses snprintf return values, leading to a buffer overflow in lat

CVE-2020-7039 MEDIUM
5.6 Jan 16

tcp_emu in tcp_subr.c in libslirp 4.1.0, as used in QEMU 4.2.0, mismanages memory, as demonstrated by IRC DCC commands i

CVE-2020-29129 MEDIUM
4.3 Nov 26

ncsi.c in libslirp through 4.3.1 has a buffer over-read because it tries to read a certain amount of header data even if

CVE-2021-3594 LOW
3.8 Jun 15

An invalid pointer initialization issue was found in the SLiRP networking implementation of QEMU. Rated low severity (CV

CVE-2021-3593 LOW
3.8 Jun 15

An invalid pointer initialization issue was found in the SLiRP networking implementation of QEMU. Rated low severity (CV

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