CVE-2025-39673

Summary

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.

Affected Software

VendorProductVersion RangeStatus
LinuxLinuxf6efc675c9dd8d93f826b79ae7e33e03301db609 < 9a1969fbffc1f1900d92d7594b1b7d8d72ef3dc7affected
LinuxLinuxf6efc675c9dd8d93f826b79ae7e33e03301db609 < 0f1630be6fcca3f0c63e4b242ad202e5cde28a40affected
LinuxLinuxf6efc675c9dd8d93f826b79ae7e33e03301db609 < ca18d751bcc9faf5b7e82e9fae1223d103928181affected
LinuxLinuxf6efc675c9dd8d93f826b79ae7e33e03301db609 < 94731cc551e29511d85aa8dec61a6c071b1f2430affected
LinuxLinuxf6efc675c9dd8d93f826b79ae7e33e03301db609 < f97f6475fdcb3c28ff3c55cc4b7bde632119ec08affected
LinuxLinuxf6efc675c9dd8d93f826b79ae7e33e03301db609 < 0417adf367a0af11adf7ace849af4638cfb573f7affected
LinuxLinux5.13affected
LinuxLinux0 < 5.13unaffected
LinuxLinux5.15.190 <= 5.15.*unaffected
LinuxLinux6.1.149 <= 6.1.*unaffected
LinuxLinux6.6.103 <= 6.6.*unaffected
LinuxLinux6.12.44 <= 6.12.*unaffected
LinuxLinux6.16.4 <= 6.16.*unaffected
LinuxLinux6.17 <= *unaffected

Weaknesses

ADP Enrichment

CVE Program Container

Additional References

Additional References

References