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Full vulnerability report · 2021
CVE-2021-3516High confidence

There's a flaw in libxml2's xmllint in versions before 2.9.11

n/a · libxml2

7.8HighCVSS 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
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
There's a flaw in libxml2's xmllint in versions before 2.9.11. An attacker who is able to submit a crafted file to be processed by xmllint could trigger a use-after-free. The greatest impact of this flaw is to confidentiality, integrity, and availability.
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.

Select the national-authority views to include. The exact source language is shown on each matched advisory. Your choice is remembered on this device and encoded in the shareable URL.

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-2021-26834

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

There's a flaw in libxml2's xmllint in versions before 2.9.11. An attacker who is able to submit a crafted file to be processed by xmllint could trigger a use-after-free. The greatest impact of this flaw is to confidentiality, integrity, and availability.

What

There's a flaw in libxml2's xmllint in versions before 2.9.11. An attacker who is able to submit a crafted file to be processed by xmllint could trigger a use-after-free. The greatest impact of this flaw is to confidentiality, integrity, and availability.

Why

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

How

An attacker operating through local access may attempt exploitation without authentication after a user interaction. If successful, the issue may cause the confidentiality, integrity or availability impact described by the vendor.

What

There's a flaw in libxml2's xmllint in versions before 2.9.11. An attacker who is able to submit a crafted file to be processed by xmllint could trigger a use-after-free. The greatest impact of this flaw is to confidentiality, integrity, and availability.

Why

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

How

An attacker operating through local access may attempt exploitation without authentication after a user interaction. 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.
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 → Use After Free → cause the confidentiality, integrity or availability impact described by the vendor
Attack surface
Local
Privileges required
None: unauthenticated exploitation is possible
User interaction
Required interaction required
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:L/AC:L/PR:N/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.

AVLocalAttack vector: The attacker needs local access to the vulnerable system.ACLowAttack complexity: No specialised conditions are required beyond attacker-controlled input.PRNonePrivileges required: The attacker does not need an account or existing 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
The issue can support a local privilege or sandbox boundary transition; normal system utilities may then be available in the gained context.
UnauthenticatedCWE-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-W-2025-0227IBM QRadar SIEM: Mehrere Schwachstellen

Ein entfernter, authentisierter Angreifer kann mehrere Schwachstellen in IBM QRadar SIEM ausnutzen, um seine Privilegien zu erweitern, Administratorrechte zu erlangen, beliebigen Programmcode auszuführen, Informationen offenzulegen, Dateien zu manipulieren oder Sicherheitsvorkehrungen zu umgehen.

Official advisory
BSI · German · WID-SEC-W-2023-1152libxml2: Mehrere Schwachstellen ermöglichen nicht spezifizierten Angriff

Ein entfernter, anonymer Angreifer kann mehrere Schwachstellen in libxml2 ausnutzen, um einen nicht näher spezifizierten Angriff durchzuführen.

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

ERecord?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-2021-33294 Référence CVE CVE-2021-33560 https://www.cve.org/CVERecord?id=CVE-2021-33560 Référence CVE CVE-2021-33574 https://www.cve.org/CVERecord?id=CVE-2021-33574 Référence CVE CVE-2021-33910 https://www.cve.org/CVERecord?id=CVE-2021-33910 Référence CVE CVE-2021-3426 https://www.cve.org/CVERecord?id=CVE-2021-3426 Référence CVE CVE-2021-3516 https://www.cve.org/CVERecord?id=CVE-2021-3516 Référence CVE CVE-2021-3517 https://www.cve.org/CVERecord?id=CVE-2021-3517 Référence CVE CVE-2021-3518 https://www.cve.org/CVERecord?id=CVE-2021-3518 Référence CVE CVE-2021-3520 https://www.cve.org/CVERecord?id=CVE-2021-3520 Référence CVE CVE-2021-3537 https://www.cve.org/CVERecord?id=CVE-2021-3537 Référence CVE CVE-2021-3541 https://www.cve.org/CVERecord?id=CVE-2021-3541 Référence CVE CVE-2021-3580 https://www.cve.org/CVERecord?id=CVE-2021-3580 Référence CVE CVE-2021-35942 https://www.cve.org/CVERecord?id=CVE-2021-35942 Référence CVE CVE-2021-36084 https://www.cve.org/CVERecord?id=CVE-2021-3608

Official advisory
CERT-FR · French · CERTFR-2023-AVI-0362Multiples vulnérabilités dans les produits IBM

6505 du 05 mai 2023 https://www.ibm.com/support/pages/node/6986505 Bulletin de sécurité IBM 6987769 du 02 mai 2023 https://www.ibm.com/support/pages/node/6987769 Bulletin de sécurité IBM 6988147 du 05 mai 2023 https://www.ibm.com/support/pages/node/6988147 Référence CVE CVE-2015-5237 https://www.cve.org/CVERecord?id=CVE-2015-5237 Référence CVE CVE-2020-7598 https://www.cve.org/CVERecord?id=CVE-2020-7598 Référence CVE CVE-2020-7789 https://www.cve.org/CVERecord?id=CVE-2020-7789 Référence CVE CVE-2021-22569 https://www.cve.org/CVERecord?id=CVE-2021-22569 Référence CVE CVE-2021-29469 https://www.cve.org/CVERecord?id=CVE-2021-29469 Référence CVE CVE-2021-3516 https://www.cve.org/CVERecord?id=CVE-2021-3516 Référence CVE CVE-2021-3518 https://www.cve.org/CVERecord?id=CVE-2021-3518 Référence CVE CVE-2021-39036 https://www.cve.org/CVERecord?id=CVE-2021-39036 Référence CVE CVE-2021-44906 https://www.cve.org/CVERecord?id=CVE-2021-44906 Référence CVE CVE-2022-0185 https://www.cve.org/CVERecord?id=CVE-2022-0185 Référence CVE CVE-2022-21680 https://www.cve.org/CVERecord?id=CVE-2022-21680 Référence CVE CVE-2022-21681 https://www.cve.org/CVERecord?id=CVE-2022-21681 Référence CVE CVE-2022-24434 https://www.cve.org/CVERecord?id=CVE-2022-24434 Référence CVE CVE-2022-24728 https://www.cve.org/CVERecord?id=CVE-2

Official advisory
CERT-FR · French · CERTFR-2021-AVI-791Multiples vulnérabilités dans les produits IBM

g/CVERecord?id=CVE-2021-29745 Référence CVE CVE-2021-29894 https://www.cve.org/CVERecord?id=CVE-2021-29894 Référence CVE CVE-2021-30661 https://www.cve.org/CVERecord?id=CVE-2021-30661 Référence CVE CVE-2021-3177 https://www.cve.org/CVERecord?id=CVE-2021-3177 Référence CVE CVE-2021-3326 https://www.cve.org/CVERecord?id=CVE-2021-3326 Référence CVE CVE-2021-33910 https://www.cve.org/CVERecord?id=CVE-2021-33910 Référence CVE CVE-2021-3421 https://www.cve.org/CVERecord?id=CVE-2021-3421 Référence CVE CVE-2021-3449 https://www.cve.org/CVERecord?id=CVE-2021-3449 Référence CVE CVE-2021-3450 https://www.cve.org/CVERecord?id=CVE-2021-3450 Référence CVE CVE-2021-3516 https://www.cve.org/CVERecord?id=CVE-2021-3516 Référence CVE CVE-2021-3517 https://www.cve.org/CVERecord?id=CVE-2021-3517 Référence CVE CVE-2021-3518 https://www.cve.org/CVERecord?id=CVE-2021-3518 Référence CVE CVE-2021-3520 https://www.cve.org/CVERecord?id=CVE-2021-3520 Référence CVE CVE-2021-3537 https://www.cve.org/CVERecord?id=CVE-2021-3537 Référence CVE CVE-2021-3541 https://www.cve.org/CVERecord?id=CVE-2021-3541 Référence CVE CVE-2021-3609 https://www.cve.org/CVERecord?id=CVE-2021-3609 Gestion détaillée du document le 15 octobre 2021 Version initiale Alertes Avis Bulletins d’actualités Mentions légales Conditions générales À propos Con

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
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)
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
Update to V3.1.5 or later version
Workaround
No verified workaround is recorded. Limit untrusted access and use least privilege until authoritative guidance is available.
04

Evidence and provenance

Published 1 Jun 2021 · Last source change 3 Aug 2024, 16:53 UTC · CWE-416 · Use After 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-2021-26834
Product sourceVendor CSAF · Siemens ProductCERT
Remediation sourceVendor CSAF · Siemens ProductCERT
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-2021-26834↗Vendor CSAF · Siemens ProductCERT↗Patch or update reference↗Patch or update reference↗CVE authority or vendor 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-2021-3516 · cve.blacktree.nl