CVE-2020-1983 | libslirp: use after free vulnerability cause a denial of service.

Exp

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.

Published: 2020-04-22 Last update: 2026-06-16 Assigner: [email protected] Source: [email protected]
NVD Status：Modified，CVE State: published
View at NVD, CVE.org, EUVD

CVE-2020-1983 is rated High Exploit Risk (75.5/100): CVSS High severity, with medium exploitation likelihood (EPSS 2.29%). 1 public exploit reference(s) are indexed (Exploit-DB). EPSS rose +2.15% over the last day, indicating growing attacker interest. Public exploits are available—assess exposure, apply mitigations, and prioritize patching.

Risk is dynamic; we continuously reassess and refresh what is shown on this page as upstream context changes.

Public exploit references (Exploit-DB) for CVE-2020-1983

EDB-ID Source Kind Published Link
— nvd_ref exploit_tag Exploit-DB ↗

Exploit prediction scoring system (EPSS) score for CVE-2020-1983

EPSS lead: Daily EPSS estimates relative likelihood of exploitation; percentile ranks this CVE among scored vulnerabilities (higher = more severe relative rank).

# Date Old EPSS score New EPSS score Delta (New - Old)
1 2026-06-15 0.15% 2.29% +2.15%
2 2026-04-21 0.20% 0.15% -0.05%
3 2025-12-28 — 0.20% —

Full EPSS history (18 records total)

Common vulnerability scoring system (CVSS) metrics for CVE-2020-1983

CVSS metrics for this CVE.

Base score Version Severity Vector Exploitability Impact Score source
7.5 3.1 HIGH
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H Click to expand
Attack vector (AV:N)
Could be attacked over the internet or any normal routed network—not just someone sitting at the machine.
Attack complexity (AC:L)
Once they can reach the bug, pulling it off is straightforward—no weird race conditions or rare setup.
Privileges required (PR:N)
No account or special rights needed—anonymous or random user is enough.
User interaction (UI:N)
Nobody has to click “OK” or open a trap file; it can work without a victim helping.
Scope (S:U)
Damage stays in the same “trust bubble” as the broken component—no big spill into unrelated systems.
Confidentiality (C:N)
Doesn’t really leak secrets in a meaningful way.
Integrity (I:N)
Data isn’t meaningfully altered or forged.
Availability (A:H)
Could take the service down hard or make it unusable for people who depend on it.
 3.9 3.6 [email protected]
6.5 3.1 MEDIUM
CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:C/C:N/I:N/A:H Click to expand
Attack vector (AV:L)
They already need access on the box, or another person has to do something wrong; it’s not a remote drive-by.
Attack complexity (AC:L)
Once they can reach the bug, pulling it off is straightforward—no weird race conditions or rare setup.
Privileges required (PR:L)
A normal user session is enough; they don’t have to be admin.
User interaction (UI:N)
Nobody has to click “OK” or open a trap file; it can work without a victim helping.
Scope (S:C)
Breaking this can reach past the original component and bite other resources—bigger blast radius.
Confidentiality (C:N)
Doesn’t really leak secrets in a meaningful way.
Integrity (I:N)
Data isn’t meaningfully altered or forged.
Availability (A:H)
Could take the service down hard or make it unusable for people who depend on it.
 2.0 4.0 [email protected]
2.1 2.0 LOW
AV:L/AC:L/Au:N/C:N/I:N/A:P Click to expand
Access vector (AV:L)
Requires local access to the target system.
Access complexity (AC:L)
Exploitation conditions are straightforward and predictable.
Authentication (AU:N)
No authentication is required.
Confidentiality impact (C:N)
No confidentiality impact.
Integrity impact (I:N)
No integrity impact.
Availability impact (A:P)
Partial availability impact.
 3.9 2.9 [email protected]

Weakness enumeration for CVE-2020-1983

OS Trackers for CVE-2020-1983

vendor priority summary link
alpine medium CVE-2020-1983: 1 source package rows (libslirp); 7 state rows across 7 repos (3.17-community, 3.18-community, 3.19-community, 3.20-community, 3.21-community, 3.22-community, edge-community); fixed 7, open 0. https://security.alpinelinux.org/vuln/CVE-2020-1983
debian not yet assigned CVE-2020-1983 not yet assigned priority: Debian including 3 source packages (libslirp, qemu, slirp4netns), 15 status rows across 5 suites (bookworm, bullseye, forky, sid, trixie): resolved 15. https://security-tracker.debian.org/tracker/CVE-2020-1983
redhat medium — https://access.redhat.com/security/cve/CVE-2020-1983
suse high CVE-2020-1983 severity important: SUSE including 895 source package names (amazon/suse-sles-15-sp1-chost-byos-v20210304-hvm-ssd-x86_64, amazon/suse-sles-15-sp1-chost-byos-v20220127-hvm-ssd-x86_64, …), 1317 product×package rows across 68 product lines (HPE Helion OpenStack 8, Image SLES12-SP5-EC2-ECS-On-Demand, … (68 product lines)): Fixed 983, Known Affected 231, Known Not Affected 103. https://www.suse.com/security/cve/CVE-2020-1983/
ubuntu medium CVE-2020-1983 medium priority: Ubuntu including 4 source packages (libslirp, qemu, qemu-kvm, slirp4netns), 68 status rows across 17 suites (bionic, eoan, focal, groovy, hirsute, impish, jammy, kinetic, lunar, mantic, noble, oracular, plucky, questing, trusty, upstream, xenial): DNE 23, not-affected 23, released 16, needs-triage 5, ignored 1. https://ubuntu.com/security/CVE-2020-1983

Affected software / configurations for CVE-2020-1983

Vendor Product Version Raw CPE
libslirp_project libslirp <= 4.2.0 cpe:2.3:a:libslirp_project:libslirp:*:*:*:*:*:*:*:*
fedoraproject fedora 31 cpe:2.3:o:fedoraproject:fedora:31:*:*:*:*:*:*:*
fedoraproject fedora 32 cpe:2.3:o:fedoraproject:fedora:32:*:*:*:*:*:*:*
debian debian_linux 8.0 cpe:2.3:o:debian:debian_linux:8.0:*:*:*:*:*:*:*
debian debian_linux 9.0 cpe:2.3:o:debian:debian_linux:9.0:*:*:*:*:*:*:*
opensuse leap 15.1 cpe:2.3:o:opensuse:leap:15.1:*:*:*:*:*:*:*
canonical ubuntu_linux 16.04 cpe:2.3:o:canonical:ubuntu_linux:16.04:*:*:*:esm:*:*:*
canonical ubuntu_linux 18.04 cpe:2.3:o:canonical:ubuntu_linux:18.04:*:*:*:lts:*:*:*
canonical ubuntu_linux 19.10 cpe:2.3:o:canonical:ubuntu_linux:19.10:*:*:*:*:*:*:*
canonical ubuntu_linux 20.04 cpe:2.3:o:canonical:ubuntu_linux:20.04:*:*:*:lts:*:*:*

References for CVE-2020-1983

URL Tags
http://lists.opensuse.org/opensuse-security-announce/2020-05/msg00022.html Mailing List Third Party Advisory
http://lists.opensuse.org/opensuse-security-announce/2020-06/msg00001.html Mailing List Third Party Advisory
https://gitlab.freedesktop.org/slirp/libslirp/-/commit/9ac0371bb8c0a40f5d9f82a1c25129660e81df04 Patch Third Party Advisory
https://gitlab.freedesktop.org/slirp/libslirp/-/issues/20 Exploit Third Party Advisory
https://lists.debian.org/debian-lts-announce/2020/06/msg00032.html Mailing List Third Party Advisory
https://lists.debian.org/debian-lts-announce/2020/07/msg00020.html Mailing List Third Party Advisory
https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/HWFD4MWV3YWIHVHSA2F7FKOLJFL4PHOX/
https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/NKT2MTSINE4NUPG5L6BYH6N23NBNITOL/
https://usn.ubuntu.com/4372-1/ Third Party Advisory
https://www.debian.org/security/2020/dsa-4665 Third Party Advisory
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