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Fencer Intel
medium 4.3

CVE-2020-29129 json

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 that exceeds the t…

published 5y ago modified 4mo ago also EUVD-2020-21510

cvss
4.3
version 3.1, NVD
cisa kev
Not listed
not in CISA's catalog
epss
1.5%
EPSS 1.5% chance of exploitation in 30 days, percentile 73%
public exploits
0
none known

Summary

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 that exceeds the total packet length.

Patch / fix

  • qemu Debian 14, Debian 13, Debian 12 1:4.1-2
  • libslirp Debian 14, Debian 13, Debian 12 4.4.0-1

debian advisories DEBIAN-CVE-2020-29129

  • libslirp Ubuntu 20.04 LTS 4.1.0-2ubuntu2.2

ubuntu advisories UBUNTU-CVE-2020-29129

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 RHEL 8 20191022-3.git899d9883.module+el8.3.0+6423+e4cb6418
  • hivex RHEL 8 1.3.18-20.module+el8.3.0+6423+e4cb6418
  • netcf RHEL 8 0.2.8-12.module+el8.1.0+4066+0f1aadab
  • libnbd RHEL 8 1.2.2-1.module+el8.3.0+7353+9de0a3cc
  • nbdkit RHEL 8 1.16.2-4.module+el8.3.0+6922+fd575af8
  • libvirt RHEL 8 6.0.0-35.module+el8.4.0+10230+7a9b21e4
  • nbdfuse RHEL 8 1.2.2-1.module+el8.3.0+7353+9de0a3cc
  • seabios RHEL 8 1.13.0-2.module+el8.3.0+7353+9de0a3cc

red hat advisories RHSA-2021:1762

  • slirp4netns SLE Micro 5.1, openSUSE Leap Micro 5.3, Enterprise Storage 7 0.4.7-150100.3.18.1
  • qemu SLES for SAP 12 SP4, SLES 12 SP4-LTSS, OpenStack Cloud Crowbar 9 +1 more 2.11.2-5.32.1
  • qemu SLE Module for Server Applications 15 SP3, SLE Module for Basesystem 15 SP3 5.2.0-17.1
  • qemu SLES for SAP 15 SP1, SLES 15 SP1-LTSS, SLES 15 SP1-BCL +7 more 3.1.1.1-9.27.2
  • qemu SLES for SAP 15, SLES 15-LTSS, SLE High Performance Computing 15-LTSS +1 more 2.11.2-9.46.1
  • qemu SLE Module for Server Applications 15 SP2, SLE Module for Basesystem 15 SP2, SLE Micro 5.0 4.2.1-11.19.2
  • qemu SLES for SAP 12 SP5, SLES 12 SP5 3.1.1.1-51.1
  • qemu SLES for SAP 15 SP1, SLES 15 SP1-LTSS, SLES 15 SP1-BCL +6 more 3.1.1.1-9.24.3

suse advisories SUSE-SU-2023:0870-1SUSE-SU-2021:1947-1SUSE-SU-2021:1942-1SUSE-SU-2021:1918-1SUSE-SU-2021:1895-1SUSE-SU-2021:1893-1

  • qemu openSUSE Tumbleweed 6.1.0-32.1
  • qemu openSUSE Leap 15.2 4.2.1-lp152.9.16.2
  • qemu-testsuite openSUSE Leap 15.2 4.2.1-lp152.9.16.7
  • qemu-linux-user openSUSE Leap 15.2 4.2.1-lp152.9.16.1
  • qemu openSUSE Leap 15.3 5.2.0-17.1
  • qemu openSUSE Leap 15.2 4.2.1-lp152.9.12.1
  • qemu-testsuite openSUSE Leap 15.2 4.2.1-lp152.9.12.1
  • qemu-linux-user openSUSE Leap 15.2 4.2.1-lp152.9.12.1

opensuse advisories openSUSE-SU-2024:11287-1openSUSE-SU-2021:1043-1openSUSE-SU-2021:1942-1openSUSE-SU-2021:0600-1

  • 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
  • nbdfuse AlmaLinux 8 1.2.2-1.module_el8.3.0+2048+e7a0a3ea

almalinux advisories ALSA-2021:1762

  • 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
  • libvirt Rocky Linux 8 6.0.0-35.module+el8.4.0+534+4680a14e
  • seabios Rocky Linux 8 1.13.0-2.module+el8.4.0+534+4680a14e

rocky linux advisories RLSA-2021:1762

  • libslirp Alpine 3.24, Alpine 3.23, Alpine 3.22 +9 more 4.4.0-r0

alpine advisories ALPINE-CVE-2020-29129

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

  • libslirp Arch Linux 4.4.0-1

arch linux advisories AVG-1305

Is CVE-2020-29129 in your stack? Fencer shows which of your repositories are affected as soon as an advisory lands, and opens the fix as a pull request.

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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-2020-29129 updated cvss 2.5

QEMU: slirp: out-of-bounds access while processing ARP/NCSI packets

  • Red Hat Enterprise Linux 5 kvm Red Hat Enterprise Linux 6 qemu-img, qemu-kvm, qemu-kvm-tools, qemu-guest-agent, qemu-guest-agent-win32
    affected: no fix planned “Out of support scope”
  • Red Hat Enterprise Linux 7 qemu-img, qemu-kvm, libcacard, qemu-img-ma, qemu-kvm-ma, qemu-img-rhev, +9 more
    affected: no fix available “Fix deferred”
  • Red Hat Enterprise Linux 8 Advanced Virtualization qemu-img, qemu-kvm, qemu-kiwi, qemu-kvm-core, qemu-kvm-tests, qemu-kvm-common, +9 more
    affected: no fix available
  • 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, seabios 1.13.0-2.module+el8.3.0+7353+9de0a3cc, libiscsi 1.18.0-8.module+el8.1.0+4066+0f1aadab, +39 more Red Hat Enterprise Linux AppStream (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, nbdkit 1.16.2-4.module+el8.3.0+6922+fd575af8, seabios 1.13.0-2.module+el8.3.0+7353+9de0a3cc, +88 more
    fixed: vendor fix RHSA-2021:1762
  • Red Hat Enterprise Linux 5 xen
    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

1.46% chance of exploitation in the next 30 days, higher than 73% of all scored CVEs (FIRST EPSS, 2026-11-09).

CVSS scores

assigned by version score vector
NVD 3.1 4.3 CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:L/I:N/A:N
NVD 2.0 4.0 AV:N/AC:L/Au:S/C:P/I:N/A:N

Classification

Weakness

References

Sources

Fencer Intel 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.