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Fencer Vulns
high 7.5

CVE-2020-1983 json

libslirp: use after free vulnerability cause a denial of service.

published 2020-04-22 6 y ago modified 2026-06-17 4 mo ago also EUVD-2020-12773

cvss
7.5
version 3.1, CNA
cisa kev
Not listed
not in CISA's catalog
epss
2.4%
EPSS 2.4% chance of exploitation in 30 days, percentile 83%
public exploits
0
none known

Summary

A use after free vulnerability in ip_reass() in ip_input.c of libslirp 4.2.0 and prior releases allows crafted packets to cause a denial of service.

Patch / fix

  • qemu Debian 14, Debian 13, Debian 12 1:4.1-2
  • libslirp Debian 14, Debian 13, Debian 12 4.2.0-2
  • slirp4netns Debian 14, Debian 13, Debian 12 1.0.1-1

debian advisories DEBIAN-CVE-2020-1983

  • qemu Ubuntu 16.04 LTS 1:2.5+dfsg-5ubuntu10.44
  • qemu Ubuntu 18.04 LTS 1:2.11+dfsg-1ubuntu7.26
  • libslirp Ubuntu 20.04 LTS 4.1.0-2ubuntu2
  • qemu Ubuntu Pro 14.04 LTS 2.0.0+dfsg-2ubuntu1.47+esm4

ubuntu advisories UBUNTU-CVE-2020-1983

Ubuntu security data © Canonical Ltd., from https://github.com/canonical/ubuntu-security-notices via OSV; changed: normalised to fixed package versions per release. CC BY-SA 4.0

  • SLOF advanced virtualization 8.2 20191022-3.git899d9883.module+el8.2.0+5449+efc036dd
  • hivex advanced virtualization 8.2 1.3.18-20.module+el8.2.0+5588+63a201c3
  • netcf advanced virtualization 8.2 0.2.8-12.module+el8.2.0+4793+b09dd2fb
  • swtpm advanced virtualization 8.2 0.2.0-2.20200127gitff5a83b.module+el8.2.0+5579+d71178e0
  • libnbd advanced virtualization 8.2 1.2.2-1.module+el8.2.0+5644+32ac38d4
  • nbdkit advanced virtualization 8.2 1.16.2-4.module+el8.2.1+6710+effcb1df
  • libtpms advanced virtualization 8.2 0.7.0-1.20191018gitdc116933b7.module+el8.2.0+4793+b09dd2fb
  • libvirt advanced virtualization 8.2 6.0.0-25.module+el8.2.1+7154+47ffd890

red hat advisories RHBA-2020:3172RHSA-2020:3053RHSA-2020:4676RHSA-2020:4290RHSA-2020:4079RHSA-2021:0934

  • kvm SLE Point of Sale 11 SP3 1.4.2-53.38.1
  • qemu SLES for SAP 12 SP3, SLES 12 SP3-LTSS, SLES 12 SP3-BCL +4 more 2.9.1-6.44.1
  • qemu SLES for SAP 12 SP2, SLES 12 SP2-LTSS, SLES 12 SP2-BCL +1 more 2.6.2-41.59.1
  • qemu SLES for SAP 15, SLES 15-LTSS, SLE High Performance Computing 15-LTSS +1 more 2.11.2-9.36.1
  • qemu SLES for SAP 12 SP5, SLES 12 SP5 3.1.1.1-3.14.1
  • qemu SLE Module for Server Applications 15 SP1, SLE Module for Basesystem 15 SP1 3.1.1.1-9.21.4
  • qemu SLES for SAP 12 SP4, SLES 12 SP4 2.11.2-5.26.1
  • slirp4netns SLE Module for Containers 15 SP1 0.4.5-3.9.1

suse advisories SUSE-SU-2021:14706-1SUSE-SU-2020:14396-1SUSE-SU-2020:1538-1SUSE-SU-2020:1526-1SUSE-SU-2020:1523-1SUSE-SU-2020:1516-1

  • libslirp openSUSE Tumbleweed 4.6.1+7-1.2
  • qemu openSUSE Tumbleweed 6.1.0-32.1
  • qemu openSUSE Leap 15.1 3.1.1.1-lp151.7.15.2
  • qemu-linux-user openSUSE Leap 15.1 3.1.1.1-lp151.7.15.2
  • slirp4netns openSUSE Leap 15.1 0.4.5-lp151.2.9.1

opensuse advisories openSUSE-SU-2024:10991-1openSUSE-SU-2024:11287-1openSUSE-SU-2020:0756-1openSUSE-SU-2020:0636-1

  • hivex AlmaLinux 8 1.3.18-20.module_el8.3.0+2048+e7a0a3ea
  • netcf AlmaLinux 8 0.2.8-12.module_el8.5.0+2608+72063365
  • netcf AlmaLinux 8 0.2.8-12.module_el8.6.0+2880+7d9e3703
  • netcf AlmaLinux 8 0.2.8-12.module_el8.3.0+2048+e7a0a3ea
  • libnbd AlmaLinux 8 1.2.2-1.module_el8.5.0+2608+72063365
  • libnbd AlmaLinux 8 1.2.2-1.module_el8.3.0+2048+e7a0a3ea
  • nbdkit AlmaLinux 8 1.16.2-4.module_el8.5.0+2608+72063365
  • libvirt AlmaLinux 8 6.0.0-28.module_el8.3.0+2048+e7a0a3ea

almalinux advisories ALSA-2020:4676ALSA-2020:3053

  • hivex Rocky Linux 8 1.3.18-20.module+el8.4.0+534+4680a14e
  • netcf Rocky Linux 8 0.2.8-12.module+el8.7.0+1084+97b81f61
  • netcf Rocky Linux 8 0.2.8-12.module+el8.4.0+534+4680a14e
  • netcf Rocky Linux 8 0.2.8-12.module+el8.6.0+847+b490afdd
  • libnbd Rocky Linux 8 1.2.2-1.module+el8.4.0+534+4680a14e
  • nbdkit Rocky Linux 8 1.16.2-4.module+el8.4.0+534+4680a14e
  • seabios Rocky Linux 8 1.13.0-2.module+el8.4.0+534+4680a14e
  • sgabios Rocky Linux 8 1:0.20170427git-3.module+el8.7.0+1084+97b81f61

rocky linux advisories RLSA-2020:4676RLSA-2020:3053

  • libslirp Alpine 3.24, Alpine 3.23, Alpine 3.22 +9 more 4.3.0-r0

alpine advisories ALPINE-CVE-2020-1983

Alpine secdb © Alpine Linux, from https://secdb.alpinelinux.org via OSV; changed: normalised to fixed package versions per release. CC BY-SA 4.0

Vendor advisories

What the vendors themselves say about their products: affected, fixed or not affected, and what to do.

red hat product security vex CVE-2020-1983 updated cvss 6.5

QEMU: slirp: use-after-free in ip_reass() function in ip_input.c

  • Red Hat Enterprise Linux 5 kvm
    affected: no fix planned “Out of support scope”
  • Red Hat Enterprise Linux 6 qemu-img, qemu-kvm, qemu-kvm-tools, qemu-guest-agent, qemu-guest-agent-win32 Red Hat Enterprise Linux 7 slirp4netns
    affected: no fix planned “Will not fix”
  • Red Hat Enterprise Linux 8 slirp4netns
    affected: no fix available, no fix planned “Out of support scope”
  • Red Hat Enterprise Linux 8 Advanced Virtualization qemu-img, qemu-kvm, qemu-kiwi, qemu-kvm-core, qemu-kvm-tests, qemu-kvm-common, +9 more Red Hat OpenShift Container Platform 4 slirp4netns
    affected: no fix available
  • Red Hat OpenStack Platform 10 (Newton) qemu-img-rhev, qemu-kvm-rhev, qemu-kvm-tools-rhev, qemu-kvm-common-rhev
    affected: no fix planned “Out of support scope”
  • Red Hat Advanced Virtualization CodeReady Builder for RHEL 8.1.1 hivex 1.3.15-7.module+el8.1.1+5309+6d656f05, libnbd 1.0.3-1.module+el8.1.1+5659+15cacc69, netcf 0.2.8-12.module+el8.1.1+5309+6d656f05, libvirt 5.6.0-10.module+el8.1.1+5309+6d656f05, seabios 1.12.0-5.module+el8.1.1+5309+6d656f05, libiscsi 1.18.0-8.module+el8.1.1+5309+6d656f05, +44 more
    fixed: vendor fix RHSA-2020:4290
  • Red Hat Advanced Virtualization CodeReady Builder for RHEL 8.2.1 libnbd 1.2.2-1.module+el8.2.0+5644+32ac38d4, netcf 0.2.8-12.module+el8.2.0+4793+b09dd2fb, hivex 1.3.18-20.module+el8.2.0+5588+63a201c3, nbdfuse 1.2.2-1.module+el8.2.0+5644+32ac38d4, libvirt 6.0.0-25.module+el8.2.1+7154+47ffd890, seabios 1.13.0-2.module+el8.2.1+7284+aa32a2c4, +45 more
    fixed: vendor fix RHBA-2020:3172
  • Red Hat Advanced Virtualization for RHEL 8.1.1 hivex 1.3.15-7.module+el8.1.1+5309+6d656f05, libnbd 1.0.3-1.module+el8.1.1+5659+15cacc69, netcf 0.2.8-12.module+el8.1.1+5309+6d656f05, nbdkit 1.12.5-2.module+el8.1.1+5309+6d656f05, libvirt 5.6.0-10.module+el8.1.1+5309+6d656f05, seabios 1.12.0-5.module+el8.1.1+5309+6d656f05, +96 more
    fixed: vendor fix RHSA-2020:4290
show 9 more
  • Red Hat Advanced Virtualization for RHEL 8.2.1 libnbd 1.2.2-1.module+el8.2.0+5644+32ac38d4, netcf 0.2.8-12.module+el8.2.0+4793+b09dd2fb, hivex 1.3.18-20.module+el8.2.0+5588+63a201c3, nbdfuse 1.2.2-1.module+el8.2.0+5644+32ac38d4, nbdkit 1.16.2-4.module+el8.2.1+6710+effcb1df, libvirt 6.0.0-25.module+el8.2.1+7154+47ffd890, +96 more
    fixed: vendor fix RHBA-2020:3172
  • Red Hat CodeReady Linux Builder (v. 8) libnbd 1.2.2-1.module+el8.3.0+7353+9de0a3cc, netcf 0.2.8-12.module+el8.1.0+4066+0f1aadab, hivex 1.3.18-20.module+el8.3.0+6423+e4cb6418, nbdfuse 1.2.2-1.module+el8.3.0+7353+9de0a3cc, libvirt 6.0.0-28.module+el8.3.0+7827+5e65edd7, seabios 1.13.0-2.module+el8.3.0+7353+9de0a3cc, +39 more
    fixed: vendor fix RHSA-2020:4676
  • Red Hat Enterprise Linux AppStream (v. 8) crit 3.14-2.module+el8.2.1+6750+e53a300c, criu 3.14-2.module+el8.2.1+6750+e53a300c, udica 0.2.1-2.module+el8.2.1+6465+1a51e8b6, libnbd 1.2.2-1.module+el8.3.0+7353+9de0a3cc, netcf 0.2.8-12.module+el8.1.0+4066+0f1aadab, podman 1.9.3-2.module+el8.2.1+6867+366c07d6, +111 more
    fixed: vendor fix RHSA-2020:3053
  • Red Hat Enterprise Linux Client (v. 7) qemu-img 1.5.3-175.el7_9.1, qemu-kvm 1.5.3-175.el7_9.1, qemu-kvm-tools 1.5.3-175.el7_9.1, qemu-kvm-common 1.5.3-175.el7_9.1 Red Hat Enterprise Linux ComputeNode Optional (v. 7) qemu-img 1.5.3-175.el7_9.1, qemu-kvm 1.5.3-175.el7_9.1, qemu-kvm-tools 1.5.3-175.el7_9.1, qemu-kvm-common 1.5.3-175.el7_9.1 Red Hat Enterprise Linux Server (v. 7) qemu-img 1.5.3-175.el7_9.1, qemu-kvm 1.5.3-175.el7_9.1, qemu-img-ma 2.12.0-48.el7_9.2, qemu-kvm-ma 2.12.0-48.el7_9.2, qemu-kvm-tools 1.5.3-175.el7_9.1, qemu-kvm-common 1.5.3-175.el7_9.1, +2 more
    fixed: vendor fix RHSA-2020:4079
  • Red Hat Enterprise Linux Server Optional (v. 7) qemu-kvm-ma 2.12.0-48.el7_9.2, qemu-kvm-tools-ma 2.12.0-48.el7_9.2, qemu-kvm-common-ma 2.12.0-48.el7_9.2
    fixed: vendor fix RHSA-2021:0346
  • Red Hat Enterprise Linux Workstation (v. 7) qemu-img 1.5.3-175.el7_9.1, qemu-kvm 1.5.3-175.el7_9.1, qemu-kvm-tools 1.5.3-175.el7_9.1, qemu-kvm-common 1.5.3-175.el7_9.1
    fixed: vendor fix RHSA-2020:4079
  • Red Hat OpenStack Platform 13.0 qemu-img-rhev 2.12.0-48.el7_9.2, qemu-kvm-rhev 2.12.0-48.el7_9.2, qemu-kvm-tools-rhev 2.12.0-48.el7_9.2, qemu-kvm-common-rhev 2.12.0-48.el7_9.2
    fixed: vendor fix RHSA-2021:0934
  • Red Hat Virtualization 4 Management Agent for RHEL 7 Hosts qemu-img-rhev 2.12.0-48.el7_9.2, qemu-kvm-rhev 2.12.0-48.el7_9.2, qemu-kvm-tools-rhev 2.12.0-48.el7_9.2, qemu-kvm-common-rhev 2.12.0-48.el7_9.2 Red Hat RHV-M 4.3 qemu-img-rhev 2.12.0-48.el7_9.2, qemu-kvm-rhev 2.12.0-48.el7_9.2, qemu-kvm-tools-rhev 2.12.0-48.el7_9.2, qemu-kvm-common-rhev 2.12.0-48.el7_9.2
    fixed: vendor fix RHSA-2021:0459
  • Red Hat Enterprise Linux 8 Advanced Virtualization qemu-img, qemu-kvm, qemu-kiwi, qemu-kvm-core, qemu-kvm-tests, qemu-kvm-common, +9 more Red Hat Enterprise Linux 9 qemu-img, qemu-kvm, qemu-kvm-core, qemu-kvm-tools, qemu-pr-helper, qemu-kvm-common, +16 more
    not affected: vulnerable code not present

Red Hat CSAF VEX © Red Hat, Inc., from https://security.access.redhat.com/data/csaf/v2/vex/; changed: reduced to product statuses and remediations. CC BY 4.0 · csaf

Exploit prediction

2.36% chance of exploitation in the next 30 days, higher than 83% of all scored CVEs (FIRST EPSS, 2026-11-08).

Exploits and checks

  • gitlab.freedesktop.org https://gitlab.freedesktop.org/slirp/libslirp/-/issues/20 referenced PoC, tagged "exploit" by a source, unverified

CVSS scores

assigned by version score vector
CNA 3.1 7.5 CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
NVD 3.1 6.5 CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:C/C:N/I:N/A:H
NVD 2.0 2.1 AV:L/AC:L/Au:N/C:N/I:N/A:P

Affected products

  • slirp libslirp

Classification

Weakness

References

Sources

Fencer Vulns keeps one entry per vulnerability: the CVE id wins, then GHSA, and records that alias each other are merged, except that two CVEs always keep separate entries. The same data is available as JSON.