by Kastro
Paper/Archive/CVE-2025-39673

CVE-2025-39673

Linux Linux — ppp: fix race conditions in ppp_fill_forward_path

EPSS 0.3%CVSS 9.8
critical.is priorityof 100
34
CVSS 9.8 (CNA)9.8 / 10 × 3029.4Not in CISA KEV+300.0EPSS percentile 23.6.236 × 204.7No public exploit+100.0SSVC exploitation: none+100.0
Description · from the CVE record

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

ProductAffectedFixed inSource
Linuxf6efc675c9dd8d93f826b79ae7e33e03301db609 – < 9a1969fbffc1f1900d92d7594b1b7d8d72ef3dc79a1969fbffc1f1900d92d7594b1b7d8d72ef3dc7CNA
Linuxf6efc675c9dd8d93f826b79ae7e33e03301db609 – < 0f1630be6fcca3f0c63e4b242ad202e5cde28a400f1630be6fcca3f0c63e4b242ad202e5cde28a40CNA
Linuxf6efc675c9dd8d93f826b79ae7e33e03301db609 – < ca18d751bcc9faf5b7e82e9fae1223d103928181ca18d751bcc9faf5b7e82e9fae1223d103928181CNA
Linuxf6efc675c9dd8d93f826b79ae7e33e03301db609 – < 94731cc551e29511d85aa8dec61a6c071b1f243094731cc551e29511d85aa8dec61a6c071b1f2430CNA
Linuxf6efc675c9dd8d93f826b79ae7e33e03301db609 – < f97f6475fdcb3c28ff3c55cc4b7bde632119ec08f97f6475fdcb3c28ff3c55cc4b7bde632119ec08CNA
Linuxf6efc675c9dd8d93f826b79ae7e33e03301db609 – < 0417adf367a0af11adf7ace849af4638cfb573f70417adf367a0af11adf7ace849af4638cfb573f7CNA
Linux5.135.15.190CNA
SIMATIC CN 4100< V5.0V5.0siemens-SADP

Scores by source

Linux (CNA)9.8CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
CISA ADPSSVCExploitation: none · Automatable: yes · Technical impact: total

References

refgit.kernel.org/stable/c/9a1969fbffc1f1900d92d7594b1b7d8d72ef3dc7refgit.kernel.org/stable/c/0f1630be6fcca3f0c63e4b242ad202e5cde28a40refgit.kernel.org/stable/c/ca18d751bcc9faf5b7e82e9fae1223d103928181refgit.kernel.org/stable/c/94731cc551e29511d85aa8dec61a6c071b1f2430refgit.kernel.org/stable/c/f97f6475fdcb3c28ff3c55cc4b7bde632119ec08refgit.kernel.org/stable/c/0417adf367a0af11adf7ace849af4638cfb573f7reflists.debian.org/debian-lts-announce/2025/10/msg00008.htmlrefcert-portal.siemens.com/productcert/html/ssa-032379.html