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Full vulnerability report · 2021
CVE-2021-28041High confidence

n/a — Double Free

Unknown · Unknown

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

7.1HighCVSS 3.1
Recommended action
Patch only the product branches with a verified fix

High technical severity; prioritise exposed affected systems while verifying vendor guidance. Verified remediation exists for at least one product or source, but 7 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 severityHighOperational priority:High, unchanged from published severity.unchanged

Evidence used

  • No CISA KEV confirmation is currently recorded.
  • EPSS is 3.42% 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.
  • Monitor vendor guidance and exploitation sources for a material change.

Verification

  1. Confirm that the asset runs Unknown Unknown 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 30 daysRemediation target: Within 180 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 7 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

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

7 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 · mainopensshVendor fix publishedAlpine records a security fix at this version. An absent entry does not mean the package is unaffected.8.5_p1-r0Alpine Security Database ↗Source updated 3 Oct 2026
Alpine v3.22v3.22 · mainopensshVendor fix publishedAlpine records a security fix at this version. An absent entry does not mean the package is unaffected.8.5_p1-r0Alpine Security Database ↗Source updated 3 Oct 2026
Alpine v3.21v3.21 · mainopensshVendor fix publishedAlpine records a security fix at this version. An absent entry does not mean the package is unaffected.8.5_p1-r0Alpine Security Database ↗Source updated 3 Oct 2026
Debian trixietrixie · sourceopensshVendor fix publishedDebian records a fixed source-package version for this release.1:8.4p1-5Debian Security Tracker ↗Source updated 5 Oct 2026
Debian bookwormbookworm · sourceopensshVendor fix publishedDebian records a fixed source-package version for this release.1:8.4p1-5Debian Security Tracker ↗Source updated 5 Oct 2026
Debian forkyforky · sourceopensshVendor fix publishedDebian records a fixed source-package version for this release.1:8.4p1-5Debian Security Tracker ↗Source updated 5 Oct 2026
Debian sidsid · sourceopensshVendor fix publishedDebian records a fixed source-package version for this release.1:8.4p1-5Debian Security Tracker ↗Source updated 5 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.

3 current
SCA-2025-0011 · CSAF 2.0 · revision 1.0.0 · finalSICK PSIRTVulnerabilities affecting Endress+Hauser SSG-E210GC
1 known affected

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

  • Endress+Hauser SSG-E210GC all Firmware versions
Summary
SSH-agent in OpenSSH before 8.5 has a double free that may be relevant in a few less-common scenarios, such as unconstrained agent-socket access on a legacy operating system, or the forwarding of an agent to an attacker-controlled host.
Remediation
Please make sure that only trusted entities have access to the device. Furthermore, you should apply the following General Security Measures when operating the product to mitigate the associated security risk. The collected resources "SICK Operating Guidelines" and "ICS-CERT recommended practices on Industrial Security" could help to implement the general security practices.
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
ssh-agent in OpenSSH before 8.5 has a double free that may be relevant in a few less-common scenarios, such as unconstrained agent-socket access on a legacy operating system, or the forwarding of an agent to an attacker-controlled host.
Remediation
Update to V3.1.5 or later version
SCA-2025-0009 · CSAF 2.0 · revision 1 · finalSICK PSIRTVulnerabilities affecting SICK TDC-E210GC
1 known affected

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

  • SICK TDC-E210GC all Firmware versions
Summary
SSH-agent in OpenSSH before 8.5 has a double free that may be relevant in a few less-common scenarios, such as unconstrained agent-socket access on a legacy operating system, or the forwarding of an agent to an attacker-controlled host.
Remediation
Please make sure that only trusted entities have access to the device. Furthermore, you should apply the following General Security Measures when operating the product to mitigate the associated security risk. The collected resources "SICK Operating Guidelines" and "ICS-CERT recommended practices on Industrial Security" could help to implement the general security practices.
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-2021-14748

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

High technical severity; prioritise exposed affected systems while verifying vendor guidance. Verified remediation exists for at least one product or source, but 7 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

ssh-agent in OpenSSH before 8.5 has a double free that may be relevant in a few less-common scenarios, such as unconstrained agent-socket access on a legacy operating system, or the forwarding of an agent to an attacker-controlled host.

What

ssh-agent in OpenSSH before 8.5 has a double free that may be relevant in a few less-common scenarios, such as unconstrained agent-socket access on a legacy operating system, or the forwarding of an agent to an attacker-controlled host.

Why

The product calls free() twice on the same memory address.

How

An attacker operating through a network path may attempt exploitation with low privileges. If successful, the issue may cause the confidentiality, integrity or availability impact described by the vendor.

What

ssh-agent in OpenSSH before 8.5 has a double free that may be relevant in a few less-common scenarios, such as unconstrained agent-socket access on a legacy operating system, or the forwarding of an agent to an attacker-controlled host.

Why

The product calls free() twice on the same memory address.

How

An attacker operating through a network path may attempt exploitation with low privileges. If successful, the issue may cause the confidentiality, integrity or availability impact described by the vendor.

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.
None recorded

No exploit-tagged reference or CISA SSVC proof-of-concept state is currently recorded. Research may still exist outside the structured feeds.

Likely attack path
a network path → Double Free → cause the confidentiality, integrity or availability impact described by the vendor
Attack surface
Network
Privileges required
Low: a basic authenticated account is required
User interaction
Required interaction required
Attack complexity
High: exploitation depends on specific conditions
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-415 ↗

CWE-415: Double Free. The product calls free() twice on the same memory address.

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:H/PR:L/UI:R/S:U/C:H/I:H/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.ACHighAttack complexity: Successful exploitation depends on specific conditions outside the attacker's direct control.PRLowPrivileges required: The attacker needs basic user-level privileges.UIRequiredUser interaction: Another user must perform an action for exploitation to succeed.SUnchangedScope: The security impact remains within the vulnerable component's authority.CHighConfidentiality impact: A successful attack can cause a major loss.IHighIntegrity impact: A successful attack can cause a major loss.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.
NetworkCWE-415
A

Official authority intelligence

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

BSI · German · WID-SEC-2024-1082Juniper JUNOS: Mehrere Schwachstellen

Ein Angreifer kann mehrere Schwachstellen in Juniper JUNOS im Zusammenhang mit OpenSSH ausnutzen, um Sicherheitsmaßnahmen zu umgehen, beliebigen Code auszuführen oder Dateien zu manipulieren.

Official advisory ↗
BSI · German · WID-SEC-2023-0997OpenSSH: Schwachstelle ermöglicht Codeausführung

Ein entfernter, authentisierter Angreifer kann eine Schwachstelle in OpenSSH ausnutzen, um beliebigen Programmcode auszuführen.

Official advisory ↗
Cyber Security Agency of Singapore · English · CSA-SB-20210310Security Bulletin 10 Mar 2021

The Cyber Security Agency of Singapore included this CVE in its official Security Bulletin 10 Mar 2021, published on 10 March 2021. Open the linked bulletin for the product, severity and reference information published in that issue.

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

d?id=CVE-2021-22926 Référence CVE CVE-2021-22945 https://www.cve.org/CVERecord?id=CVE-2021-22945 Référence CVE CVE-2021-22946 https://www.cve.org/CVERecord?id=CVE-2021-22946 Référence CVE CVE-2021-22947 https://www.cve.org/CVERecord?id=CVE-2021-22947 Référence CVE CVE-2021-23336 https://www.cve.org/CVERecord?id=CVE-2021-23336 Référence CVE CVE-2021-27212 https://www.cve.org/CVERecord?id=CVE-2021-27212 Référence CVE CVE-2021-27218 https://www.cve.org/CVERecord?id=CVE-2021-27218 Référence CVE CVE-2021-27219 https://www.cve.org/CVERecord?id=CVE-2021-27219 Référence CVE CVE-2021-27645 https://www.cve.org/CVERecord?id=CVE-2021-27645 Référence CVE CVE-2021-28041 https://www.cve.org/CVERecord?id=CVE-2021-28041 Référence CVE CVE-2021-28153 https://www.cve.org/CVERecord?id=CVE-2021-28153 Référence CVE CVE-2021-28363 https://www.cve.org/CVERecord?id=CVE-2021-28363 Référence CVE CVE-2021-28861 https://www.cve.org/CVERecord?id=CVE-2021-28861 Référence CVE CVE-2021-31239 https://www.cve.org/CVERecord?id=CVE-2021-31239 Référence CVE CVE-2021-3177 https://www.cve.org/CVERecord?id=CVE-2021-3177 Référence CVE CVE-2021-32292 https://www.cve.org/CVERecord?id=CVE-2021-32292 Référence CVE CVE-2021-3326 https://www.cve.org/CVERecord?id=CVE-2021-3326 Référence CVE CVE-2021-33294 https://www.cve.org/CVERecord?id=CVE-

Official advisory ↗
JVN iPedia · Japanese · JVNDB-2021-003866OpenSSH における二重解放に関する脆弱性

OpenSSH には、二重解放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
Endress+Hauser SSG-E210GC all Firmware versions
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
Please make sure that only trusted entities have access to the device. Furthermore, you should apply the following General Security Measures when operating the product to mitigate the associated security risk. The collected resources "SICK Operating Guidelines" and "ICS-CERT recommended practices on Industrial Security" could help to implement the general security practices.
04

Evidence and provenance

Published 5 Mar 2021 · Last source change 3 Aug 2024, 21:33 UTC · CWE-415 · Double Free

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-2021-14748
Product sourceVendor CSAF · SICK PSIRT
Remediation sourceVendor CSAF · SICK PSIRT
CWE sourceNIST NVD
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. Vendor guidanceAuthoritative vendor guidance changed: added remediation: sick.com/sca-2025-0011.json; removed remediation: endress.com.
    Before
    remediation: endress.com
    After
    remediation: sick.com/sca-2025-0011.json
    SICK PSIRT ↗
  2. Affected versionsThe structured affected or fixed version information changed.
    Before
    n/a · 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
    n/a · Fixed: Update to V3.1.5 or later version
    Siemens ProductCERT ↗
  3. Vendor guidanceAuthoritative vendor guidance changed: added remediation: sick.com/special_information_sick_operating_guidelines_cybersecurity_by_sick_en_im0106719.pdf; removed remediation: sick.com/psirt.
    Before
    remediation: sick.com/psirt
    After
    remediation: sick.com/special_information_sick_operating_guidelines_cybersecurity_by_sick_en_im0106719.pdf
    SICK PSIRT ↗
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-2021-14748↗Vendor CSAF · SICK PSIRT↗Siemens ProductCERT security advisory · Siemens SSA-398330↗CVE authority or vendor reference↗Patch or update reference↗Patch or update reference↗Vendor advisory↗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-2021-28041 · cve.blacktree.nl