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CVE-2021-3595· NVD / CVE Program· CNA redhat

An invalid pointer initialization issue was found in the SLiRP networking implementation of QEMU.

Noroxi assessment

Priority: Monitor (action score 15/100)

  • The sources we track (CISA KEV, Exploit-DB, Metasploit, Nuclei, GitHub) show no public exploit code or exploitation in the wild.
  • Probability of exploitation in the next 30 days: 0.32% (FIRST EPSS).
  • Someone with local access to the system can trigger it. A low-privileged account is enough. No user action is required. No special conditions are required; it is repeatable.
  • Fixed version: hivex (AlmaLinux:8) 1.3.18-21.module_el8.5.0+2608+72063365; hivex-devel (AlmaLinux:8) 1.3.18-21.module_el8.5.0+2608+72063365; libguestfs (AlmaLinux:8) 1:1.40.2-28.module_el8.5.0+2608+72063365.alma.
  • Mentioned 1 time in Turkish national cyber security advisories (siberguvenlik.gov.tr).

Low priority for now. Upgrade to hivex (AlmaLinux:8) 1.3.18-21.module_el8.5.0+2608+72063365; hivex-devel (AlmaLinux:8) 1.3.18-21.module_el8.5.0+2608+72063365; libguestfs (AlmaLinux:8) 1:1.40.2-28.module_el8.5.0+2608+72063365.alma or later.

Generated automatically from the record's data: CVSS (NVD and CNA), CISA KEV and SSVC, FIRST EPSS, exploit sources, fixed versions. How we calculate it

Primary sources: NVD · CVE.org · FIRST EPSS

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.

LowCVSS 3.8 · v3.1—No exploit Fix available
Published
Jun 15, 2021
Updated
Jun 17, 2026
EPSS
0.3% · 24th percentile

Report tools

JSON

Action score

15

Monitor

Low priority for now.

CVSS
15 / 40 · 3.8 / 10
CISA KEV
0 / 30 · Not listed
EPSS
0 / 30 · 0.3%

Get told when this record changes

  • Not in KEV: no record of exploitation in the wild
  • No public exploit code on record
  • A fix has been released

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When you'll hear from us

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  • when EPSS rises 20 points in a week

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Noroxi analysis

What does it mean in your environment?

The assessment above is generated automatically from the record's data; it doesn't know your environment. Our team verifies on your systems whether this vulnerability is actually exploitable and which mitigation is enough.

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Affected systems

Is your version affected?

Pick the product and type the version you run. It's compared with this record's version ranges in your browser; the version isn't sent anywhere.

VendorProduct
libslirp projectlibslirp
redhatenterprise linux
debiandebian linux
fedoraprojectfedora

Affected versions

NVD version ranges (for catalog products). Add the product to your stack with a version and matching uses these.

  • debian debian linux9.0
  • fedoraproject fedora33
  • fedoraproject fedora34
  • libslirp project libslirpbefore 4.6.0
  • redhat enterprise linux8.0

Versions reported by the vendor

Affected version ranges reported by the assigning authority (redhat). Independent of NVD's CPE analysis and usually ahead of it.

  • n/a QEMU

    • libslirp 4.6.0affected

Package-level exposure

OSV and GitHub Advisory data: ecosystem, package and range. SBOM matching uses this table.

EcosystemPackageAffected rangeFix
AlmaLinux:8hivexbefore 1.3.18-21.module_el8.5.0+2608+720633651.3.18-21.module_el8.5.0+2608+72063365
AlmaLinux:8hivex-develbefore 1.3.18-21.module_el8.5.0+2608+720633651.3.18-21.module_el8.5.0+2608+72063365
AlmaLinux:8libguestfsbefore 1:1.40.2-28.module_el8.5.0+2608+72063365.alma1:1.40.2-28.module_el8.5.0+2608+72063365.alma
AlmaLinux:8libguestfs-bash-completionbefore 1:1.40.2-28.module_el8.5.0+2608+72063365.alma1:1.40.2-28.module_el8.5.0+2608+72063365.alma
AlmaLinux:8libguestfs-benchmarkingbefore 1:1.40.2-28.module_el8.5.0+2608+72063365.alma1:1.40.2-28.module_el8.5.0+2608+72063365.alma
AlmaLinux:8libguestfs-develbefore 1:1.40.2-28.module_el8.5.0+2608+72063365.alma1:1.40.2-28.module_el8.5.0+2608+72063365.alma
AlmaLinux:8libguestfs-gfs2before 1:1.40.2-28.module_el8.5.0+2608+72063365.alma1:1.40.2-28.module_el8.5.0+2608+72063365.alma
AlmaLinux:8libguestfs-gobjectbefore 1:1.40.2-28.module_el8.5.0+2608+72063365.alma1:1.40.2-28.module_el8.5.0+2608+72063365.alma
AlmaLinux:8libguestfs-gobject-develbefore 1:1.40.2-28.module_el8.5.0+2608+72063365.alma1:1.40.2-28.module_el8.5.0+2608+72063365.alma
AlmaLinux:8libguestfs-inspect-iconsbefore 1:1.40.2-28.module_el8.5.0+2608+72063365.alma1:1.40.2-28.module_el8.5.0+2608+72063365.alma
AlmaLinux:8libguestfs-javabefore 1:1.40.2-28.module_el8.5.0+2608+72063365.alma1:1.40.2-28.module_el8.5.0+2608+72063365.alma
AlmaLinux:8libguestfs-java-develbefore 1:1.40.2-28.module_el8.5.0+2608+72063365.alma1:1.40.2-28.module_el8.5.0+2608+72063365.alma
AlmaLinux:8libguestfs-javadocbefore 1:1.40.2-28.module_el8.5.0+2608+72063365.alma1:1.40.2-28.module_el8.5.0+2608+72063365.alma
AlmaLinux:8libguestfs-man-pages-jabefore 1:1.40.2-28.module_el8.5.0+2608+72063365.alma1:1.40.2-28.module_el8.5.0+2608+72063365.alma
AlmaLinux:8libguestfs-man-pages-ukbefore 1:1.40.2-28.module_el8.5.0+2608+72063365.alma1:1.40.2-28.module_el8.5.0+2608+72063365.alma
AlmaLinux:8libguestfs-rescuebefore 1:1.40.2-28.module_el8.5.0+2608+72063365.alma1:1.40.2-28.module_el8.5.0+2608+72063365.alma
AlmaLinux:8libguestfs-rsyncbefore 1:1.40.2-28.module_el8.5.0+2608+72063365.alma1:1.40.2-28.module_el8.5.0+2608+72063365.alma
AlmaLinux:8libguestfs-toolsbefore 1:1.40.2-28.module_el8.5.0+2608+72063365.alma1:1.40.2-28.module_el8.5.0+2608+72063365.alma
AlmaLinux:8libguestfs-tools-cbefore 1:1.40.2-28.module_el8.5.0+2608+72063365.alma1:1.40.2-28.module_el8.5.0+2608+72063365.alma
AlmaLinux:8libguestfs-winsupportbefore 8.2-1.module_el8.5.0+2608+720633658.2-1.module_el8.5.0+2608+72063365
AlmaLinux:8libguestfs-xfsbefore 1:1.40.2-28.module_el8.5.0+2608+72063365.alma1:1.40.2-28.module_el8.5.0+2608+72063365.alma
AlmaLinux:8libiscsibefore 1.18.0-8.module_el8.6.0+2880+7d9e37031.18.0-8.module_el8.6.0+2880+7d9e3703
AlmaLinux:8libiscsibefore 1.18.0-8.module_el8.5.0+2608+720633651.18.0-8.module_el8.5.0+2608+72063365
AlmaLinux:8libiscsi-develbefore 1.18.0-8.module_el8.6.0+2880+7d9e37031.18.0-8.module_el8.6.0+2880+7d9e3703

+96

Same product

libslirp project: all records

Other highest-scoring records for the same primary product.

  • CVE-2019-14378ip_reass in ip_input.c in libslirp 4.0.0 has a heap-based buffer overflow via a large packet because it mishandles a case involving the firs
    40Plan
  • CVE-2020-1983libslirp: use after free vulnerability cause a denial of service.
    27Monitor
  • CVE-2020-10756An out-of-bounds read vulnerability was found in the SLiRP networking implementation of the QEMU emulator.
    26Monitor

Published before and after this one in the same product

  • ← EarlierCVE-2021-3592Jun 15, 2021 · An invalid pointer initialization issue was found in the SLiRP networking implementation of QEMU.
    15Monitor
  • ← EarlierCVE-2021-3593Jun 15, 2021 · An invalid pointer initialization issue was found in the SLiRP networking implementation of QEMU.
    15Monitor
  • ← EarlierCVE-2021-3594Jun 15, 2021 · An invalid pointer initialization issue was found in the SLiRP networking implementation of QEMU.
    15Monitor

Remediation

Which version to upgrade to

Fix versions compiled from the vendor, package registries and Microsoft. Verify the vendor's note before upgrading.

Product / packageFixed versionSource
almalinux:hivex1.3.18-21.module_el8.5.0+2608+72063365 · AlmaLinux:8Package registry (OSV)
almalinux:hivex-devel1.3.18-21.module_el8.5.0+2608+72063365 · AlmaLinux:8Package registry (OSV)
almalinux:libguestfs1:1.40.2-28.module_el8.5.0+2608+72063365.alma · AlmaLinux:8Package registry (OSV)
almalinux:libguestfs-bash-completion1:1.40.2-28.module_el8.5.0+2608+72063365.alma · AlmaLinux:8Package registry (OSV)
almalinux:libguestfs-benchmarking1:1.40.2-28.module_el8.5.0+2608+72063365.alma · AlmaLinux:8Package registry (OSV)
almalinux:libguestfs-devel1:1.40.2-28.module_el8.5.0+2608+72063365.alma · AlmaLinux:8Package registry (OSV)
almalinux:libguestfs-gfs21:1.40.2-28.module_el8.5.0+2608+72063365.alma · AlmaLinux:8Package registry (OSV)
almalinux:libguestfs-gobject1:1.40.2-28.module_el8.5.0+2608+72063365.alma · AlmaLinux:8Package registry (OSV)
almalinux:libguestfs-gobject-devel1:1.40.2-28.module_el8.5.0+2608+72063365.alma · AlmaLinux:8Package registry (OSV)
almalinux:libguestfs-inspect-icons1:1.40.2-28.module_el8.5.0+2608+72063365.alma · AlmaLinux:8Package registry (OSV)
almalinux:libguestfs-java1:1.40.2-28.module_el8.5.0+2608+72063365.alma · AlmaLinux:8Package registry (OSV)
almalinux:libguestfs-java-devel1:1.40.2-28.module_el8.5.0+2608+72063365.alma · AlmaLinux:8Package registry (OSV)
debian:libslirp4.6.1-1 · Debian:12Package registry (OSV)
debian:qemu1:4.1-2 · Debian:12Package registry (OSV)
opensuse:libslirp4.3.1-150300.2.7.1 · openSUSE:Leap 15.3Package registry (OSV)
opensuse:qemu4.2.1-lp152.9.20.1 · openSUSE:Leap 15.2Package registry (OSV)
opensuse:qemu-linux-user4.2.1-lp152.9.20.1 · openSUSE:Leap 15.2Package registry (OSV)
opensuse:qemu-testsuite4.2.1-lp152.9.20.1 · openSUSE:Leap 15.2Package registry (OSV)
red hat:hivex0:1.3.18-21.module+el8.5.0+10709+b3edb581 · Red Hat:enterprise_linux:8::appstreamPackage registry (OSV)
red hat:hivex-debuginfo0:1.3.18-21.module+el8.5.0+10709+b3edb581 · Red Hat:enterprise_linux:8::appstreamPackage registry (OSV)
red hat:hivex-debugsource0:1.3.18-21.module+el8.5.0+10709+b3edb581 · Red Hat:enterprise_linux:8::appstreamPackage registry (OSV)
red hat:hivex-devel0:1.3.18-21.module+el8.5.0+10709+b3edb581 · Red Hat:enterprise_linux:8::appstreamPackage registry (OSV)
red hat:libguestfs1:1.40.2-28.module+el8.5.0+10717+67be7ac4 · Red Hat:enterprise_linux:8::appstreamPackage registry (OSV)
red hat:libguestfs-bash-completion1:1.40.2-28.module+el8.5.0+10717+67be7ac4 · Red Hat:enterprise_linux:8::appstreamPackage registry (OSV)
red hat:libguestfs-benchmarking1:1.40.2-28.module+el8.5.0+10717+67be7ac4 · Red Hat:enterprise_linux:8::appstreamPackage registry (OSV)
red hat:libguestfs-benchmarking-debuginfo1:1.40.2-28.module+el8.5.0+10717+67be7ac4 · Red Hat:enterprise_linux:8::appstreamPackage registry (OSV)
red hat:libguestfs-debuginfo1:1.40.2-28.module+el8.5.0+10717+67be7ac4 · Red Hat:enterprise_linux:8::appstreamPackage registry (OSV)
red hat:libguestfs-debugsource1:1.40.2-28.module+el8.5.0+10717+67be7ac4 · Red Hat:enterprise_linux:8::appstreamPackage registry (OSV)
red hat:libguestfs-devel1:1.40.2-28.module+el8.5.0+10717+67be7ac4 · Red Hat:enterprise_linux:8::appstreamPackage registry (OSV)
red hat:SLOF0:20191022-3.git899d9883.module+el8.3.0+6423+e4cb6418 · Red Hat:enterprise_linux:8::appstreamPackage registry (OSV)

+15

Exploit status

No known public exploit

No public exploit has been observed yet. That doesn't mean you're safe, only that the bar is a little higher.

Research context

For pentesters and researchers: attack profile, score disagreement, timeline, patch commits, credits, variant and chain candidates, bug bounty scope. All derived from existing data; no exploit code.

Timeline

From publication to today: proof of concept, Metasploit module, CISA KEV and fix record. Dates are as reported by the sources.

No dated events beyond publication.

EPSS, last 120 days

FIRST EPSS daily score; only changes of 0.01 or more are recorded (step chart).

Patch and commit links

Commit, PR and diff links among the references. A starting point for patch-diffing and variant hunting; fixes, not exploits.

No commit or PR link among the references.

Credits

All researchers

Finders, reporters and analysts named in the CNA record. Click a name for that researcher’s other records.

No credits in the CNA record.

Variant candidates

Same product, same weakness class, within 18 months. If the patch missed the root cause, the sibling bug is here.

No nightly-computed relations.

Chain candidates

An authentication bypass and a privilege-requiring bug in the same product, published close together: combined they may become an unauthenticated path.

—

Bug bounty scope

No known public program.

Source: bounty-targets-data (public HackerOne, Bugcrowd, Intigriti, YesWeHack listings).

National notice (Türkiye Cybersecurity Directorate / USOM)

Official security notices citing this record; remediation advice is on the agency's page.

All national notices →

Technical details

Attack conditions

  • Someone with local access to the system can trigger it.
  • A low-privileged account is enough.
  • No user action is required.
  • No special conditions are required; it is repeatable.

If successful

Confidentiality
low · data can be read
Integrity
none
Availability
none

Impact can extend beyond the vulnerable component (scope changes).

Attack vector
Local
Attack complexity
Low
Privileges required
Low
User interaction
None
Scope
Changed
Confidentiality impact
Low
Integrity impact
None
Availability impact
None

Weakness class (CWE)

CWE-824 · Access of Uninitialized Pointer

CVSS vector

CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:C/C:L/I:N/A:N

nvd-primary

Attack context

MITRE CAPEC attack patterns and ATT&CK techniques for this weakness class (CWE). A starting point for detection rules and threat hunting.

MITRE has no CAPEC/ATT&CK mapping for this CWE.

Change log

  1. Fix✗ → ✓

For records you follow, these changes also arrive as notifications. →

References

Show all references (6 more)

Vendor advisories and official records. Exploit/PoC links are deliberately left out.

All records