LiveActive security incident?Get immediate response
CVE Record

CVE-2025-39673: ppp: fix race conditions in ppp_fill_forward_path

In the Linux kernel, the following vulnerability has been resolved: ppp: fix race conditions in ppp_fill_forward_path ppp_fill_forward_path() has two race conditions: 1. The ppp->channels list can change between list_empty() and list_first_entry(), as ppp_lock() is not held. If the only channel is deleted in ppp_disconnect_channel(), list_first_entry() may access an empty head or a freed entry, and trigger a panic. 2. pch->chan can be NULL. When ppp_unregister_channel() is called, pch->chan is set to NULL before pch is removed from ppp->channels. Fix these by using a lockless RCU approach: - Use list_first_or_null_rcu() to safely test and access the first list entry. - Convert list modifications on ppp->channels to their RCU variants and add synchronize_net() after removal. - Check for a NULL pch->chan before dereferencing it.

CriticalCVSS 9.8Not KEV-listedUpdated
Discuss exposureBack to CVEs
Glexia's TakeAutomated analysiscritical

Security readout for executives and security teams

Plain-English summary

A race condition in Linux PPP channel handling can make the kernel access invalid or missing data while channels are disconnected or unregistered. The documented consequence is a kernel panic, which can interrupt affected systems. Although the supplied CVSS score is 9.8, the source description does not establish data theft, code execution, or privilege escalation.

Executive priority

Treat this as an urgent availability risk where affected systems use PPP, especially critical network or industrial assets. Patch through supported vendor channels promptly. Avoid assuming the 9.8 score proves remote compromise; current evidence specifically supports crash risk, and exploitation is not reported in the supplied sources.

Technical view

ppp_fill_forward_path() reads the PPP channel list without holding ppp_lock(). Concurrent channel removal can leave an empty list, freed entry, or NULL pch->chan dereference. The kernel fix uses RCU-safe list access and modification, waits with synchronize_net() after removal, and checks pch->chan before dereferencing it.

Likely exposure

Exposure requires an affected Linux kernel and relevant PPP functionality. The bundle identifies affected versions from 5.13 through listed later branches, but its version data is incomplete and duplicated. Confirm the running vendor kernel, PPP usage, and whether the distribution has backported one of the referenced fixes.

Exploitation context

The bundle marks this CVE as absent from KEV and provides no evidence of active exploitation or a public exploit. The documented failure mode is a race-triggered kernel panic. The supplied network-based CVSS vector is not explained by the technical description, so practical remote reachability should be validated per deployment.

Researcher notes

The core issue comprises list-removal and NULL-pointer races around ppp_fill_forward_path(). Review the referenced stable commits for branch-specific fixes. The supplied affected-version entries and CVSS impact claims require vendor-level reconciliation. Testing should focus on safe concurrency regression and system stability, without attempting production triggering.

Mitigation direction

  • Install the vendor-supported kernel update containing the applicable stable fix.
  • Follow Debian or Siemens guidance when operating their affected distributions or products.
  • Prioritize exposed, availability-sensitive systems that actively use PPP functionality.
  • If immediate updating is impossible, assess disabling unused PPP functionality under vendor guidance.

Validation and detection

  • Record each system's running kernel package and vendor build identifier.
  • Determine whether PPP is enabled, configured, or required on each system.
  • Compare vendor advisories and changelogs for a backport of the referenced fix.
  • After updating, verify the fixed kernel is running following any required reboot.
  • Monitor kernel logs for PPP-related panics or invalid-memory warnings.
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.

cve · low confidence lookup

CVE-2025-39673 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
Critical
CVSS
9.8 (3.1)
Known Exploited
No
Published

Vector: CVSS:3.1/AV:N/AC:L/PR:N/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
3Timeline events
2ADP providers
9Source links

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
9.8CVSS 3.1CriticalCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H3.95.9Linux

Vulnerability scoring details

Base CVSS 3.1 score

9.8Critical
CVSS 3.1 vector shape for CVE-2025-39673Attack VectorAttack ComplexityPrivileges RequiredUser InteractionScopeConfidentiality ImpactIntegrity ImpactAvailability Impact

Vector: CVSS:3.1/AV:N/AC:L/PR:N/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. CVE updatedCVE Program

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

ADP provider summaries

CVECVE Program Container
siemens-SADPADP container

Source materials

Affected products

Products and packages named in the record

VendorProductVersion / packageStatus
LinuxLinuxf6efc675c9dd8d93f826b79ae7e33e03301db609, f6efc675c9dd8d93f826b79ae7e33e03301db609, f6efc675c9dd8d93f826b79ae7e33e03301db609, f6efc675c9dd8d93f826b79ae7e33e03301db609, f6efc675c9dd8d93f826b79ae7e33e03301db609, f6efc675c9dd8d93f826b79ae7e33e03301db609unaffected
LinuxLinux5.13, 0, 5.15.190, 6.1.149, 6.6.103, 6.12.44, 6.16.4, 6.17affected
Weakness

CWE details

No CWE listed

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