BlackTreeCVE Intelligence
← Back to the CVE catalogue
Full vulnerability report · 2020
CVE-2020-1983High confidence

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

slirp · libslirp

7.5HighCVSS 3.1
Recommended action
Within 7 days

High technical severity with public exploit material referenced by a structured source; prioritise exposed affected systems while verifying vendor guidance.

Patch available
R
Operational reassessment

Published severity in operational context

Open reassessment dashboard →
Published severityHighOperational priority:Critical, raised one band.upgradedsince 16 Sep 2024

Evidence used

  • No CISA KEV confirmation is currently recorded.
  • A structured source references public exploit or proof-of-concept material.
  • The selected CVSS metric records a network-reachable, unauthenticated path with no user interaction.
  • EPSS is 2.36% for the current model date.

Compensating controls

  • Validate the affected product branch and deploy the verified fixed release.
  • Restrict the affected network interface to trusted sources where business-safe.
  • Increase monitoring for the attack path and post-exploitation behaviour described in the report.

Verification

  1. Confirm that the asset runs slirp libslirp and falls inside the recorded affected range.
  2. Verify the installed build against the product-specific fixed version after deployment.
  3. Validate exposure, authentication requirements and compensating controls in the actual environment.
  4. Reopen this reassessment when CVSS, KEV, EPSS, exploit evidence or remediation changes.
Mitigation target: Within 3 daysRemediation target: Within 90 days

This automated reassessment organises public evidence. It does not know asset exposure, business impact or control effectiveness and does not replace CVSS or a human risk decision.

Distribution package intelligence

Release-specific package status

Alpine, Debian findings are scoped to the named distribution, release and source package. An absent finding does not mean a package is unaffected.

15 package states
Repository candidate not checked

A published vendor fix does not prove that a matching update is enabled and installable on a particular asset. Confirm the local package candidate before scheduling remediation.

Distribution releaseSource packageVendor stateFixed versionEvidence
Alpine v3.23v3.23 · communitylibslirpVendor fix publishedAlpine records a security fix at this version. An absent entry does not mean the package is unaffected.4.3.0-r0Alpine Security Database ↗Source updated 22 Oct 2026
Alpine v3.22v3.22 · communitylibslirpVendor fix publishedAlpine records a security fix at this version. An absent entry does not mean the package is unaffected.4.3.0-r0Alpine Security Database ↗Source updated 22 Oct 2026
Alpine v3.21v3.21 · communitylibslirpVendor fix publishedAlpine records a security fix at this version. An absent entry does not mean the package is unaffected.4.3.0-r0Alpine Security Database ↗Source updated 22 Oct 2026
Debian trixietrixie · sourcelibslirpVendor fix publishedDebian records a fixed source-package version for this release.4.2.0-2Debian Security Tracker ↗Source updated 23 Oct 2026
Debian trixietrixie · sourceqemuVendor fix publishedDebian records a fixed source-package version for this release.1:4.1-2Debian Security Tracker ↗Source updated 23 Oct 2026
Debian trixietrixie · sourceslirp4netnsVendor fix publishedDebian records a fixed source-package version for this release.1.0.1-1Debian Security Tracker ↗Source updated 23 Oct 2026
Debian bookwormbookworm · sourcelibslirpVendor fix publishedDebian records a fixed source-package version for this release.4.2.0-2Debian Security Tracker ↗Source updated 23 Oct 2026
Debian bookwormbookworm · sourceqemuVendor fix publishedDebian records a fixed source-package version for this release.1:4.1-2Debian Security Tracker ↗Source updated 23 Oct 2026
Debian bookwormbookworm · sourceslirp4netnsVendor fix publishedDebian records a fixed source-package version for this release.1.0.1-1Debian Security Tracker ↗Source updated 23 Oct 2026
Debian forkyforky · sourcelibslirpVendor fix publishedDebian records a fixed source-package version for this release.4.2.0-2Debian Security Tracker ↗Source updated 23 Oct 2026
Debian forkyforky · sourceqemuVendor fix publishedDebian records a fixed source-package version for this release.1:4.1-2Debian Security Tracker ↗Source updated 23 Oct 2026
Debian forkyforky · sourceslirp4netnsVendor fix publishedDebian records a fixed source-package version for this release.1.0.1-1Debian Security Tracker ↗Source updated 23 Oct 2026
Debian sidsid · sourcelibslirpVendor fix publishedDebian records a fixed source-package version for this release.4.2.0-2Debian Security Tracker ↗Source updated 23 Oct 2026
Debian sidsid · sourceqemuVendor fix publishedDebian records a fixed source-package version for this release.1:4.1-2Debian Security Tracker ↗Source updated 23 Oct 2026
Debian sidsid · sourceslirp4netnsVendor fix publishedDebian records a fixed source-package version for this release.1.0.1-1Debian Security Tracker ↗Source updated 23 Oct 2026
Optional official sources

National CERT insights
?CERT means Computer Emergency Response Team; CSIRT is the closely related term Computer Security Incident Response Team.

Choose official national sources for this report. Each advisory shows its original language. Your selection is remembered on this device and included in shared links.

Official European source

ENISA European Vulnerability Database

Official EUVD identifiers, advisory evidence and known-exploited context. Missing fields are not treated as evidence of low risk.

1 current
ENISA EUVD identifier

EUVD-2020-12773

No EUVD known-exploited evidence

ENISA has published the identifier mapping but no EUVD description has been stored yet.

EUVD state
Present in the current official mapping
Known exploitation
Not present in the current ENISA EUVD known-exploited dataset. This is not proof of no exploitation.
ENISA score
Not supplied in the stored EUVD record
Advisory evidence
No linked advisory details stored yet
Recommended actionWithin 7 days

High technical severity with public exploit material referenced by a structured source; prioritise exposed affected systems while verifying vendor guidance.

Patch available
01

What, why and how

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.

What

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.

Why

The program can continue using memory after it has been released, producing unsafe and attacker-influenceable behaviour.

How

An attacker operating through a network path may attempt exploitation without authentication or user interaction. If successful, the issue may disrupt the affected service.

What

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.

Why

The program can continue using memory after it has been released, producing unsafe and attacker-influenceable behaviour.

How

An attacker operating through a network path may attempt exploitation without authentication or user interaction. If successful, the issue may disrupt the affected service.

02

Exploit reality and attack path

CVSS severity, EPSS forecast probability, public exploit material and CISA-confirmed exploitation are separate signals.

Observed exploitation
?Confirmed exploitation and public exploit material are separate signals. Attacks can occur without public proof-of-concept or exploit code.
No confirmed evidence

No CISA KEV match was present at the last successful refresh. This means no confirmation from that source, not proof of no exploitation.

Public PoC / exploit material
?Confirmed exploitation and public exploit material are separate signals. Attacks can occur without public proof-of-concept or exploit code.
Reference recorded

A structured CVE source labels at least one public reference as exploit material. BlackTree has not independently validated that it is safe, reliable or weaponised.

Likely attack path
a network path → Use After Free → disrupt the affected service
Attack surface
Network
Privileges required
None: unauthenticated exploitation is possible
User interaction
None
Attack complexity
Low: no specialised conditions are recorded
Security boundary
Unchanged: impact remains within the vulnerable component's security authority
Weakness
?CWE means Common Weakness Enumeration: a standard category for the underlying weakness.
CWE-416 ↗

CWE-416: Use After Free. The product reuses or references memory after it has been freed. At some point afterward, the memory may be allocated again and saved in another pointer, while the original pointer references a location somewhere within the new allocation. Any operations using the original pointer are no longer valid because the memory belongs to the code that operates on the new pointer.

CVSS vector
?CVSS means Common Vulnerability Scoring System. The vector records the metric values used to calculate technical severity.
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

Common Vulnerability Scoring System 3.1: the compact vector below is decoded into plain language.

AVNetworkAttack vector: The vulnerable component can be reached over a network.ACLowAttack complexity: No specialised conditions are required beyond attacker-controlled input.PRNonePrivileges required: The attacker does not need an account or existing privileges.UINoneUser interaction: No action by another user is required.SUnchangedScope: The security impact remains within the vulnerable component's authority.CNoneConfidentiality impact: No direct loss is represented by this metric.INoneIntegrity impact: No direct loss is represented by this metric.AHighAvailability impact: A successful attack can cause a major loss.
Post-exploitation / living off the land
No specific living-off-the-land technique is confirmed in the structured sources. Monitor normal administration tools for activity inconsistent with the affected service's baseline.
NetworkUnauthenticatedDenial of serviceCWE-416Public exploit reference
A

Official authority intelligence

Only matched European and national findings are included. Language selectors and unavailable sources are omitted.

BSI · German · WID-SEC-2026-0778Dell Secure Connect Gateway Policy Manager: Mehrere Schwachstellen

Ein Angreifer kann mehrere Schwachstellen in Dell Secure Connect Gateway Policy Manager ausnutzen, um einen nicht näher spezifizierten Angriff durchzuführen.

Official advisory ↗
BSI · German · WID-SEC-2026-0757Red Hat Enterprise Linux: Schwachstelle ermöglicht Denial of Service

Ein lokaler Angreifer kann eine Schwachstelle in Red Hat Enterprise Linux ausnutzen, um einen Denial of Service Angriff durchzuführen.

Official advisory ↗
Cyber Security Agency of Singapore · English · CSA-SB-20200429Security Bulletin 29 Apr 2020

The Cyber Security Agency of Singapore included this CVE in its official Security Bulletin 29 Apr 2020, published on 29 April 2020. Open the linked bulletin for the product, severity and reference information published in that issue.

Official advisory ↗
CERT-FR · French · CERTFR-2024-AVI-0997Multiples vulnérabilités dans le noyau Linux d'Ubuntu

embre 2024 https://ubuntu.com/security/notices/USN-7071-2 Bulletin de sécurité Ubuntu USN-7088-5 du 14 novembre 2024 https://ubuntu.com/security/notices/USN-7088-5 Bulletin de sécurité Ubuntu USN-7089-5 du 14 novembre 2024 https://ubuntu.com/security/notices/USN-7089-5 Bulletin de sécurité Ubuntu USN-7110-1 du 14 novembre 2024 https://ubuntu.com/security/notices/USN-7110-1 Bulletin de sécurité Ubuntu USN-7089-6 du 15 novembre 2024 https://ubuntu.com/security/notices/USN-7089-6 Référence CVE CVE-2019-20382 https://www.cve.org/CVERecord?id=CVE-2019-20382 Référence CVE CVE-2020-13765 https://www.cve.org/CVERecord?id=CVE-2020-13765 Référence CVE CVE-2020-1983 https://www.cve.org/CVERecord?id=CVE-2020-1983 Référence CVE CVE-2020-7039 https://www.cve.org/CVERecord?id=CVE-2020-7039 Référence CVE CVE-2020-8608 https://www.cve.org/CVERecord?id=CVE-2020-8608 Référence CVE CVE-2021-3592 https://www.cve.org/CVERecord?id=CVE-2021-3592 Référence CVE CVE-2021-3594 https://www.cve.org/CVERecord?id=CVE-2021-3594 Référence CVE CVE-2021-47212 https://www.cve.org/CVERecord?id=CVE-2021-47212 Référence CVE CVE-2022-36402 https://www.cve.org/CVERecord?id=CVE-2022-36402 Référence CVE CVE-2022-48666 https://www.cve.org/CVERecord?id=CVE-2022-48666 Référence CVE CVE-2023-3019 https://www.cve.org/CVERecord?id=CVE-2023-3

Official advisory ↗
CERT-FR · French · CERTFR-2022-AVI-267Multiples vulnérabilités dans Juniper Networks Junos Space

ord?id=CVE-2020-14331 Référence CVE CVE-2020-14363 https://www.cve.org/CVERecord?id=CVE-2020-14363 Référence CVE CVE-2020-14364 https://www.cve.org/CVERecord?id=CVE-2020-14364 Référence CVE CVE-2020-14385 https://www.cve.org/CVERecord?id=CVE-2020-14385 Référence CVE CVE-2020-15705 https://www.cve.org/CVERecord?id=CVE-2020-15705 Référence CVE CVE-2020-15706 https://www.cve.org/CVERecord?id=CVE-2020-15706 Référence CVE CVE-2020-15707 https://www.cve.org/CVERecord?id=CVE-2020-15707 Référence CVE CVE-2020-15999 https://www.cve.org/CVERecord?id=CVE-2020-15999 Référence CVE CVE-2020-1749 https://www.cve.org/CVERecord?id=CVE-2020-1749 Référence CVE CVE-2020-1983 https://www.cve.org/CVERecord?id=CVE-2020-1983 Référence CVE CVE-2020-24394 https://www.cve.org/CVERecord?id=CVE-2020-24394 Référence CVE CVE-2020-25212 https://www.cve.org/CVERecord?id=CVE-2020-25212 Référence CVE CVE-2020-25637 https://www.cve.org/CVERecord?id=CVE-2020-25637 Référence CVE CVE-2020-25643 https://www.cve.org/CVERecord?id=CVE-2020-25643 Référence CVE CVE-2020-2732 https://www.cve.org/CVERecord?id=CVE-2020-2732 Référence CVE CVE-2020-5208 https://www.cve.org/CVERecord?id=CVE-2020-5208 Référence CVE CVE-2020-6829 https://www.cve.org/CVERecord?id=CVE-2020-6829 Référence CVE CVE-2020-7039 https://www.cve.org/CVERecord?id=CVE-2020

Official advisory ↗
CERT-FR · French · CERTFR-2021-AVI-638Multiples vulnérabilités dans Juniper Junos Space

ecord?id=CVE-2020-13765 Référence CVE CVE-2020-14318 https://www.cve.org/CVERecord?id=CVE-2020-14318 Référence CVE CVE-2020-14323 https://www.cve.org/CVERecord?id=CVE-2020-14323 Référence CVE CVE-2020-14351 https://www.cve.org/CVERecord?id=CVE-2020-14351 Référence CVE CVE-2020-14364 https://www.cve.org/CVERecord?id=CVE-2020-14364 Référence CVE CVE-2020-1472 https://www.cve.org/CVERecord?id=CVE-2020-1472 Référence CVE CVE-2020-15862 https://www.cve.org/CVERecord?id=CVE-2020-15862 Référence CVE CVE-2020-16092 https://www.cve.org/CVERecord?id=CVE-2020-16092 Référence CVE CVE-2020-1971 https://www.cve.org/CVERecord?id=CVE-2020-1971 Référence CVE CVE-2020-1983 https://www.cve.org/CVERecord?id=CVE-2020-1983 Référence CVE CVE-2020-25211 https://www.cve.org/CVERecord?id=CVE-2020-25211 Référence CVE CVE-2020-25645 https://www.cve.org/CVERecord?id=CVE-2020-25645 Référence CVE CVE-2020-25656 https://www.cve.org/CVERecord?id=CVE-2020-25656 Référence CVE CVE-2020-25705 https://www.cve.org/CVERecord?id=CVE-2020-25705 Référence CVE CVE-2020-28374 https://www.cve.org/CVERecord?id=CVE-2020-28374 Référence CVE CVE-2020-29573 https://www.cve.org/CVERecord?id=CVE-2020-29573 Référence CVE CVE-2020-29661 https://www.cve.org/CVERecord?id=CVE-2020-29661 Référence CVE CVE-2020-7053 https://www.cve.org/CVERecord?id=CV

Official advisory ↗
JVN iPedia · Japanese · JVNDB-2020-004648libslirp における解放済みメモリの使用に関する脆弱性

libslirp には、解放済みメモリの使用に関する脆弱性が存在します。

Official advisory ↗
03

Patch and workaround

Operational remediation based on structured source evidence.

Status
?Patch availability is based on structured fixed-version fields and authoritative update references. If no fix is verified, check the vendor advisory before making a change.
Patch available
Affected
libslirp: unspecified ≤ 4.2.0
Fixed
An authoritative update reference is available, but the fixed version is not recorded in the structured CVE fields. Check the linked vendor advisory for the applicable release.
Action
Review the linked authoritative reference and apply the recorded fixed release appropriate to the affected product branch.
Workaround
No verified workaround is recorded. If business-safe, reduce exposure to the affected interface and allow only trusted sources until authoritative guidance is available.
04

Evidence and provenance

Published 22 Apr 2020 · Last source change 16 Sept 2024, 19:41 UTC · CWE-416 · Use After Free

CVE recordCVE.org · 5.1
CVSS sourceCNA
EPSS source
?The date BlackTree first stored a score for this CVE from the daily FIRST EPSS feed.
FIRST · tracked since 2026-08-14
European sourceENISA EUVD · EUVD-2020-12773
Product sourceCNA
Remediation sourceCVE/CNA references
CWE sourceCNA
NVD statusNVD modified after enrichment

Core structured fields are present and their contributing authorities are shown above.

Material change intelligence

What changed after publication

View recent updates ↗

No material field changes have been recorded since change tracking began. Routine source refreshes and cosmetic edits are intentionally excluded.

Material fields only · duplicate refreshes suppressed · history retained for the configured operational retention period
CVE published
Fixed release or patch reference recorded
ENISA EUVD · EUVD-2020-12773↗Patch or update reference↗Public exploit reference↗Official CVE record (CNA and ADP data)↗NVD record↗
Technical terms and abbreviations used in this report
CVE
Common Vulnerabilities and Exposures: the public identifier for one disclosed vulnerability.
CVSS
Common Vulnerability Scoring System: a technical severity framework; it is not patching priority by itself.
EPSS
Exploit Prediction Scoring System: FIRST's estimate of the probability that exploitation activity will be observed in the next 30 days; it is a forecast, not confirmation.
CWE
Common Weakness Enumeration: the standard category describing the underlying software or hardware weakness.
CNA
CVE Numbering Authority: an organisation authorised to assign and publish CVE records.
CISA ADP
Cybersecurity and Infrastructure Security Agency Authorized Data Publisher: structured enrichment added to a CVE record.
NVD
National Vulnerability Database: NIST's enrichment service for CVE records.
CERT / CSIRT
A computer security incident response team that publishes warnings or coordinates incident response.
PoC
Proof of concept: public material that demonstrates or helps reproduce exploitation.
CSAF
Common Security Advisory Framework: a machine-readable format for security advisories.
LoTL
Living off the land: abuse of legitimate tools or system functions during an attack.
Free version - for non-commercial use only.CVE-2020-1983 · cve.blacktree.nl