LiveActive security incident?Get immediate response
CVE Record

CVE-2021-4034: A local privilege escalation vulnerability was found on polkit's pkexec utility.

A local privilege escalation vulnerability was found on polkit's pkexec utility. The pkexec application is a setuid tool designed to allow unprivileged users to run commands as privileged users according predefined policies. The current version of pkexec doesn't handle the calling parameters count correctly and ends trying to execute environment variables as commands. An attacker can leverage this by crafting environment variables in such a way it'll induce pkexec to execute arbitrary code. When successfully executed the attack can cause a local privilege escalation given unprivileged users administrative rights on the target machine.

HighCVSS 7.8Known exploitedUpdated
Discuss exposureBack to CVEs
Glexia's TakeAutomated analysishigh

Security readout for executives and security teams

Plain-English summary

CVE-2021-4034, known as PwnKit, lets a local unprivileged user gain administrative privileges through polkit’s pkexec utility. It is not a remote entry point by itself, but it can turn a foothold into full system control. CISA lists it as known exploited, so unpatched Linux systems should be treated as urgent.

Executive priority

Prioritize remediation within the KEV-driven emergency patch process. This issue helps attackers escalate privileges after initial access, increasing ransomware and data theft impact. It is broadly relevant across Linux estates but requires local execution.

Technical view

pkexec is a setuid component in polkit. The flaw involves incorrect handling of argument count, allowing crafted environment variables to influence execution and trigger arbitrary code as root. The CVSS 3.1 score is 7.8, local attack vector, low complexity, privileges required, no user interaction, with high confidentiality, integrity, and availability impact.

Likely exposure

Exposure is likely on Linux systems with vulnerable polkit/pkexec installed. The source bundle states affected product as polkit with versions listed as all, but actual package status depends on distribution backports and vendor advisories.

Exploitation context

Active exploitation is supported by CISA KEV listing. The vulnerability requires local access or an existing low-privileged account, making it especially relevant after phishing, stolen credentials, web-shell compromise, or container/host misconfiguration.

Researcher notes

Use vendor advisories to determine fixed package versions because distributions may backport patches without changing upstream version numbers. Avoid relying only on upstream version strings. Public research confirms broad impact and details root-cause behavior; do not run proof-of-concept tests on production systems.

Mitigation direction

  • Apply vendor-provided polkit or pkexec security updates for each Linux distribution.
  • Prioritize internet-facing servers and systems with many local users.
  • If patching is delayed, check vendor guidance for supported temporary mitigations.
  • Review appliance and embedded vendor advisories where Linux components are bundled.

Validation and detection

  • Inventory systems with polkit or pkexec installed.
  • Confirm installed package versions against distribution security advisories.
  • Check whether vendor fixes or backported patches are applied.
  • Review EDR and authentication logs for suspicious local privilege escalation activity.
  • Track CISA KEV remediation expectations for enterprise prioritization.
Prepared
Confidence
high
Sources
6

Public sources used

Generated from the cited source records. This long-tail analysis has not been individually reviewed by a named human.

Potential ATT&CK relevance

Conservative CVE-to-ATT&CK context

These mappings and lookup hints may be relevant to the vulnerability behavior, CWE, affected product, or exposure path. Glexia-inferred context is not an official MITRE, ATT&CK, CWE, or CVE Program mapping.

ATT&CK lookup starting points

Use these exact CWE pages and searches to review the Glexia ATT&CK library from this CVE's weakness and description context.

cwe · low confidence lookup

CWE-787: Exact CWE lookup

Use the exact CWE identifier as the starting point before reviewing related ATT&CK behavior. Open the exact CWE lookup page first, then review the ATT&CK searches from that MITRE weakness context. This is a Glexia lookup hint, not an official ATT&CK mapping.

Open ATT&CK lookup
description · low confidence lookup

Execution behavior lookup

The CVE wording references code or command execution, so execution technique review may help defensive triage. This is a Glexia inferred lookup path, not an official MITRE, ATT&CK, or CVE Program mapping.

Open ATT&CK lookup
description · low confidence lookup

Privilege behavior lookup

The CVE wording references privilege impact, so privilege escalation and authorization behavior review may help. This is a Glexia inferred lookup path, not an official MITRE, ATT&CK, or CVE Program mapping.

Open ATT&CK lookup
cve · low confidence lookup

CVE-2021-4034 mapping review

Open the CVE-to-ATT&CK bridge for reviewed, inferred, or future official mappings tied to this CVE.

Open ATT&CK lookup
Vulnerability profileCVE Program record
Severity
High
CVSS
7.8 (3.1)
Known Exploited
Yes
Published

Vector: CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H

Official CVE source material

CNA and ADP enrichment extracted from CVE v5

These fields come from the CVE record and ADP containers, not from Glexia's Take. They preserve time-varying source decisions such as CISA SSVC, KEV status, CVSS metrics, and provider references.

1CVSS vectors
5Timeline events
2ADP providers
12Source links

CISA KEV status

Status
Known exploited
Source
CISA-ADP
Date added
KEV reference

SSVC decision data

CISA-ADPCISA Coordinator
Timestamp
Version
2.0.3
Exploitation: activeAutomatable: noTechnical Impact: total

CVSS vector scores

1 official score

We collect every scored CVSS vector available in the official CNA and ADP containers. When more than one version is present, the table keeps the source vectors side by side instead of collapsing them into the highest score.

ScoreVersionSeverityVectorExploitImpactSource
7.8CVSS 3.1HighCVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H1.85.9CISA-ADP

Vulnerability scoring details

Base CVSS 3.1 score

7.8High
CVSS 3.1 vector shape for CVE-2021-4034Attack VectorAttack ComplexityPrivileges RequiredUser InteractionScopeConfidentiality ImpactIntegrity ImpactAvailability Impact

Vector: CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H

Attack Vector
NetworkAdjacentLocalPhysical
Attack Complexity
LowHigh
Privileges Required
NoneLowHigh
User Interaction
NoneRequired
Scope
ChangedUnchanged
Confidentiality Impact
HighLowNone
Integrity Impact
HighLowNone
Availability Impact
HighLowNone

Vulnerability timeline

Timeline events are normalized from CVE metadata, CNA source timelines, ADP timelines, and KEV metadata when present.

  1. CVE reservedCVE Program

    The CVE ID was reserved by the assigning CNA.

  2. CVE publishedCVE Program

    The CVE record was published.

  3. Added to KEVCISA-ADP

    CISA Known Exploited Vulnerabilities metadata lists this CVE as known exploited.

  4. ADP timelineCISA-ADP

    CVE-2021-4034 added to CISA KEV

  5. CVE updatedCVE Program

    The CVE record metadata indicates this as the latest update time.

ADP provider summaries

CVECVE Program Container
CISA-ADPCISA ADP Vulnrichment
cvssV3_1other:ssvcother:kev
  • 2022-06-27T00:00:00.000Z: CVE-2021-4034 added to CISA KEV

Source materials

Affected products

Products and packages named in the record

VendorProductVersion / packageStatus
n/apolkitallListed
Weakness

CWE details

CWE-787

CWE links open Glexia weakness intelligence pages with official CWE context, developer remediation guidance, and related CVE mappings.

CWE-787 · source CWE mapping

Out-of-bounds Write

Out-of-bounds Write represents a recurring weakness pattern that can create exploitable paths when design, validation, or implementation controls are missing.

Open CWE intelligenceSame-CWE CVEs