BlackTreeCVE Intelligence
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Full vulnerability report · 2022
CVE-2021-3997High confidence

A flaw was found in systemd

Unknown · systemd

Official source article: Siemens SSA-398330 ↗. Check the applicable product and release in the original source.

5.5MediumCVSS 3.1
Recommended action
Patch only the product branches with a verified fix

Medium technical severity with public exploit material referenced by a structured source; prioritise exposed affected systems while verifying vendor guidance. Verified remediation exists for at least one product or source, but 5 structured product or package states remain unresolved. Apply remediation only to the exact product branch confirmed by its source.

Fix availability varies by product
R
Operational reassessment

Published severity in operational context

Open reassessment dashboard →
Published severityMediumOperational priority:Medium, unchanged from published severity.unchanged

Evidence used

  • No CISA KEV confirmation is currently recorded.
  • A structured source references public exploit or proof-of-concept material.
  • Exploitation requires an existing local or physical foothold with privileges.
  • EPSS is 1.69% for the current model date.

Compensating controls

  • Validate the affected product branch and deploy the verified fixed release.
  • Restrict local access and enforce least privilege on affected hosts.
  • Increase monitoring for the attack path and post-exploitation behaviour described in the report.

Verification

  1. Confirm that the asset runs Unknown systemd 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: As exposure requiresRemediation target: Within 365 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.

Cross-source reconciliation

Remediation availability differs by product scope

Verified remediation exists for at least one product or source, but 5 structured product or package states remain unresolved. Apply remediation only to the exact product branch confirmed by its source.

Distribution package intelligence

Release-specific package status

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

4 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
Debian trixietrixie · sourcesystemdVendor fix publishedDebian records a fixed source-package version for this release.250.2-1Debian Security Tracker ↗Source updated 6 Oct 2026
Debian bookwormbookworm · sourcesystemdVendor fix publishedDebian records a fixed source-package version for this release.250.2-1Debian Security Tracker ↗Source updated 6 Oct 2026
Debian forkyforky · sourcesystemdVendor fix publishedDebian records a fixed source-package version for this release.250.2-1Debian Security Tracker ↗Source updated 6 Oct 2026
Debian sidsid · sourcesystemdVendor fix publishedDebian records a fixed source-package version for this release.250.2-1Debian Security Tracker ↗Source updated 6 Oct 2026
Direct vendor intelligence

Authoritative vendor CSAF and VEX advisories

Structured product status and remediation from the issuing vendor. Product-state explanations are always visible; large lists can be searched or downloaded.

1 current
SSA-398330 · CSAF 2.0 · revision 18 · interimSiemens ProductCERTSSA-398330: Vulnerabilities in the additional GNU/Linux subsystem of the SIMATIC S7-1500 CPU 1518(F)-4 PN/DP MFP >= V3.1.0 and < V3.1.5
5 known affected

The vendor explicitly identifies these products as affected by this CVE.

  • SIMATIC S7-1500 CPU 1518-4 PN/DP MFP (6ES7518-4AX00-1AB0)
  • SIMATIC S7-1500 CPU 1518-4 PN/DP MFP (6ES7518-4AX00-1AC0)
  • SIMATIC S7-1500 CPU 1518F-4 PN/DP MFP (6ES7518-4FX00-1AB0)
  • SIMATIC S7-1500 CPU 1518F-4 PN/DP MFP (6ES7518-4FX00-1AC0)
  • SIPLUS S7-1500 CPU 1518-4 PN/DP MFP (6AG1518-4AX00-4AC0)
Summary
A flaw was found in systemd. An uncontrolled recursion in systemd-tmpfiles may lead to a denial of service at boot time when too many nested directories are created in /tmp.
Remediation
Update to V3.1.5 or later version
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-2021-27187

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 actionPatch only the product branches with a verified fix

Medium technical severity with public exploit material referenced by a structured source; prioritise exposed affected systems while verifying vendor guidance. Verified remediation exists for at least one product or source, but 5 structured product or package states remain unresolved. Apply remediation only to the exact product branch confirmed by its source.

Fix availability varies by product
01

What, why and how

A flaw was found in systemd. An uncontrolled recursion in systemd-tmpfiles may lead to a denial of service at boot time when too many nested directories are created in /tmp.

What

A flaw was found in systemd. An uncontrolled recursion in systemd-tmpfiles may lead to a denial of service at boot time when too many nested directories are created in /tmp.

Why

The product does not properly control the amount of recursion that takes place, consuming excessive resources, such as allocated memory or the program stack.

How

An attacker operating through local access may attempt exploitation with low privileges. If successful, the issue may disrupt the affected service.

What

A flaw was found in systemd. An uncontrolled recursion in systemd-tmpfiles may lead to a denial of service at boot time when too many nested directories are created in /tmp.

Why

The product does not properly control the amount of recursion that takes place, consuming excessive resources, such as allocated memory or the program stack.

How

An attacker operating through local access may attempt exploitation with low privileges. 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
local access → Uncontrolled Recursion → disrupt the affected service
Attack surface
Local
Privileges required
Low: a basic authenticated account is required
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-674 ↗

CWE-674: Uncontrolled Recursion. The product does not properly control the amount of recursion that takes place, consuming excessive resources, such as allocated memory or the program stack.

CVSS vector
?CVSS means Common Vulnerability Scoring System. The vector records the metric values used to calculate technical severity.
CVSS:3.1/AV:L/AC:L/PR:L/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.

AVLocalAttack vector: The attacker needs local access to the vulnerable system.ACLowAttack complexity: No specialised conditions are required beyond attacker-controlled input.PRLowPrivileges required: The attacker needs basic user-level 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
The issue can support a local privilege or sandbox boundary transition; normal system utilities may then be available in the gained context.
Denial of serviceCWE-674Public 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-2022-2277systemd: Schwachstelle ermöglicht Denial of Service

Ein lokaler Angreifer kann eine Schwachstelle in systemd ausnutzen, um einen Denial of Service Angriff durchzuführen.

Official advisory ↗
Cyber Security Agency of Singapore · English · CSA-SB-20220824Security Bulletin 24 Aug 2022

The Cyber Security Agency of Singapore included this CVE in its official Security Bulletin 24 Aug 2022, published on 24 August 2022. Open the linked bulletin for the product, severity and reference information published in that issue.

Official advisory ↗
CERT-FR · French · CERTFR-2025-AVI-0969Multiples vulnérabilités dans les produits VMware

CVERecord?id=CVE-2021-38297 Référence CVE CVE-2021-38604 https://www.cve.org/CVERecord?id=CVE-2021-38604 Référence CVE CVE-2021-39212 https://www.cve.org/CVERecord?id=CVE-2021-39212 Référence CVE CVE-2021-39293 https://www.cve.org/CVERecord?id=CVE-2021-39293 Référence CVE CVE-2021-3933 https://www.cve.org/CVERecord?id=CVE-2021-3933 Référence CVE CVE-2021-3941 https://www.cve.org/CVERecord?id=CVE-2021-3941 Référence CVE CVE-2021-39537 https://www.cve.org/CVERecord?id=CVE-2021-39537 Référence CVE CVE-2021-3995 https://www.cve.org/CVERecord?id=CVE-2021-3995 Référence CVE CVE-2021-3996 https://www.cve.org/CVERecord?id=CVE-2021-3996 Référence CVE CVE-2021-3997 https://www.cve.org/CVERecord?id=CVE-2021-3997 Référence CVE CVE-2021-3999 https://www.cve.org/CVERecord?id=CVE-2021-3999 Référence CVE CVE-2021-40211 https://www.cve.org/CVERecord?id=CVE-2021-40211 Référence CVE CVE-2021-4048 https://www.cve.org/CVERecord?id=CVE-2021-4048 Référence CVE CVE-2021-40812 https://www.cve.org/CVERecord?id=CVE-2021-40812 Référence CVE CVE-2021-41771 https://www.cve.org/CVERecord?id=CVE-2021-41771 Référence CVE CVE-2021-41772 https://www.cve.org/CVERecord?id=CVE-2021-41772 Référence CVE CVE-2021-4189 https://www.cve.org/CVERecord?id=CVE-2021-4189 Référence CVE CVE-2021-4214 https://www.cve.org/CVERecord?id=CVE-2021

Official advisory ↗
CERT-FR · French · CERTFR-2023-AVI-1015Multiples vulnérabilités dans les produits Siemens

ERecord?id=CVE-2021-36087 Référence CVE CVE-2021-36222 https://www.cve.org/CVERecord?id=CVE-2021-36222 Référence CVE CVE-2021-36690 https://www.cve.org/CVERecord?id=CVE-2021-36690 Référence CVE CVE-2021-3733 https://www.cve.org/CVERecord?id=CVE-2021-3733 Référence CVE CVE-2021-3737 https://www.cve.org/CVERecord?id=CVE-2021-3737 Référence CVE CVE-2021-37600 https://www.cve.org/CVERecord?id=CVE-2021-37600 Référence CVE CVE-2021-37750 https://www.cve.org/CVERecord?id=CVE-2021-37750 Référence CVE CVE-2021-3826 https://www.cve.org/CVERecord?id=CVE-2021-3826 Référence CVE CVE-2021-38604 https://www.cve.org/CVERecord?id=CVE-2021-38604 Référence CVE CVE-2021-3997 https://www.cve.org/CVERecord?id=CVE-2021-3997 Référence CVE CVE-2021-3998 https://www.cve.org/CVERecord?id=CVE-2021-3998 Référence CVE CVE-2021-3999 https://www.cve.org/CVERecord?id=CVE-2021-3999 Référence CVE CVE-2021-4122 https://www.cve.org/CVERecord?id=CVE-2021-4122 Référence CVE CVE-2021-41617 https://www.cve.org/CVERecord?id=CVE-2021-41617 Référence CVE CVE-2021-4189 https://www.cve.org/CVERecord?id=CVE-2021-4189 Référence CVE CVE-2021-4209 https://www.cve.org/CVERecord?id=CVE-2021-4209 Référence CVE CVE-2021-43396 https://www.cve.org/CVERecord?id=CVE-2021-43396 Référence CVE CVE-2021-43618 https://www.cve.org/CVERecord?id=CVE-2021-43

Official advisory ↗
JVN iPedia · Japanese · JVNDB-2021-020195systemd project の systemd 他複数ベンダの製品における再帰制御に関する脆弱性

systemd project の systemd 他複数ベンダの製品には、再帰制御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.
Fix availability varies by product
Affected
Fixed
Update to V3.1.5 or later version
Action
Use the product-specific evidence above. Patch only products with a verified fixed release, and keep every affected or under-investigation state without a matching fix in the remediation queue.
Workaround
No verified workaround is recorded. Limit untrusted access and use least privilege until authoritative guidance is available.
04

Evidence and provenance

Published 23 Aug 2022 · Last source change 3 Aug 2024, 17:16 UTC · CWE-674 · Uncontrolled Recursion

CVE recordCVE.org · 5.1
CVSS sourceNIST NVD
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-2021-27187
Product sourceVendor CSAF · Siemens ProductCERT
Remediation sourceVendor CSAF · Siemens ProductCERT
CWE sourceCNA
NVD statusNVD modified after enrichment

Missing structured fields: affected product. Missing data is not evidence of low risk; review the primary advisory.

Material change intelligence

What changed after publication

View recent updates ↗
  1. Affected versionsThe structured affected or fixed version information changed.
    Before
    Fixed in v251-rc1 · 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.
    After
    Fixed in v251-rc1 · Fixed: Update to V3.1.5 or later version
    Siemens ProductCERT ↗
Material fields only · duplicate refreshes suppressed · history retained for the configured operational retention period
CVE published
Fixed release or patch reference recorded
Fixed release recorded from official guidance
ENISA EUVD · EUVD-2021-27187↗Siemens ProductCERT security advisory · Siemens SSA-398330↗CVE authority or vendor reference↗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-2021-3997 · cve.blacktree.nl