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CVE Record

CVE-2018-6558: The pam_fscrypt module in fscrypt before 0.2.4 may incorrectly restore primary and supplementary group IDs...

The pam_fscrypt module in fscrypt before 0.2.4 may incorrectly restore primary and supplementary group IDs to the values associated with the root user, which allows attackers to gain privileges via a successful login through certain applications that use Linux-PAM (aka pam).

UnknownCVSS not scoredNot KEV-listedUpdated
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Glexia's TakeAutomated analysishigh

Security readout for executives and security teams

Plain-English summary

CVE-2018-6558 is a privilege escalation flaw in fscrypt's pam_fscrypt module before 0.2.4. During certain Linux-PAM logins, it may restore group IDs as root-owned values, potentially giving a logged-in attacker elevated privileges. Public sources do not show active exploitation.

Executive priority

Treat as high priority where fscrypt PAM integration is deployed, especially on shared Linux hosts. The issue can convert legitimate login access into higher privileges, but the provided evidence does not support emergency handling for active exploitation.

Technical view

The issue affects pam_fscrypt in fscrypt before 0.2.4. The module may incorrectly restore primary and supplementary group IDs to values associated with root after successful authentication through some Linux-PAM applications, creating a privilege boundary failure. The provided sources do not include CVSS, CWE, or broad affected-platform detail.

Likely exposure

Exposure is likely limited to Linux systems using fscrypt before 0.2.4 with pam_fscrypt configured in PAM login paths. Systems without pam_fscrypt in PAM, or with fscrypt 0.2.4 or later, are not shown as affected by the provided sources.

Exploitation context

The CVE describes privilege gain after a successful login through certain Linux-PAM applications. This implies an attacker likely needs valid login access or a way to authenticate through an affected PAM path. No KEV listing or provided source confirms active exploitation.

Researcher notes

Key gaps are absent CVSS/CWE data, no confirmed exploitation, and limited detail on which PAM applications trigger the faulty restoration. Validate exposure by combining package version checks with PAM configuration review rather than assuming all fscrypt installations are vulnerable.

Mitigation direction

  • Upgrade fscrypt to version 0.2.4 or a vendor-fixed package.
  • Inventory PAM configurations for pam_fscrypt usage on Linux systems.
  • Prioritize internet-facing, multi-user, and administrative login systems.
  • Review distribution guidance before altering PAM behavior.
  • Retire or isolate systems that cannot receive a fixed package.

Validation and detection

  • Check installed fscrypt versions and flag anything before 0.2.4.
  • Inspect PAM service files for pam_fscrypt references.
  • Confirm fixed builds include the referenced fscrypt commits or vendor backports.
  • Review authentication paths that allow successful user logins.
  • Monitor vendor advisories for distro-specific package status.
Prepared
Confidence
medium
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

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CVE-2018-6558 mapping review

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Vulnerability profileCVE Program record
Severity
Unknown
CVSS
Not scored
Known Exploited
No
Published
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.

0CVSS vectors
0Timeline events
0ADP providers
5Source links

CVSS and timeline data

No CVSS vectors or timeline events were available in the normalized CVE source material.

Source materials

Affected products

Products and packages named in the record

VendorProductVersion / packageStatus
The fscrypt Projectfscryptbefore 0.2.4Listed
Weakness

CWE details

No CWE listed

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