{"id":"CVE-2025-39673","title":"ppp: fix race conditions in ppp_fill_forward_path","summary":"In the Linux kernel, the following vulnerability has been resolved:\n\nppp: fix race conditions in ppp_fill_forward_path\n\nppp_fill_forward_path() has two race conditions:\n\n1. The ppp->channels list can change between list_empty() and\n   li…","severity":"critical","cvss":9.8,"cvssVector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H","cvssSource":"cna","vendor":"Linux","product":"Linux","affected":["Linux >= f6efc675c9dd8d93f826b79ae7e33e03301db609 < 9a1969fbffc1f1900d92d7594b1b7d8d72ef3dc7","Linux >= f6efc675c9dd8d93f826b79ae7e33e03301db609 < 0f1630be6fcca3f0c63e4b242ad202e5cde28a40","Linux >= f6efc675c9dd8d93f826b79ae7e33e03301db609 < ca18d751bcc9faf5b7e82e9fae1223d103928181","Linux >= f6efc675c9dd8d93f826b79ae7e33e03301db609 < 94731cc551e29511d85aa8dec61a6c071b1f2430","Linux >= f6efc675c9dd8d93f826b79ae7e33e03301db609 < f97f6475fdcb3c28ff3c55cc4b7bde632119ec08","Linux >= f6efc675c9dd8d93f826b79ae7e33e03301db609 < 0417adf367a0af11adf7ace849af4638cfb573f7","Linux 5.13"],"ssvc":{"exploitation":"none","automatable":"yes","technicalImpact":"total","timestamp":"2026-10-15T21:53:10.266228Z"},"published":"2025-09-05","updated":"2026-10-15","sourceUpdated":"2026-10-15T22:02:29.786Z","source":"CVEORG","sourceUrl":"https://www.cve.org/CVERecord?id=CVE-2025-39673","references":[{"url":"https://git.kernel.org/stable/c/9a1969fbffc1f1900d92d7594b1b7d8d72ef3dc7"},{"url":"https://git.kernel.org/stable/c/0f1630be6fcca3f0c63e4b242ad202e5cde28a40"},{"url":"https://git.kernel.org/stable/c/ca18d751bcc9faf5b7e82e9fae1223d103928181"},{"url":"https://git.kernel.org/stable/c/94731cc551e29511d85aa8dec61a6c071b1f2430"},{"url":"https://git.kernel.org/stable/c/f97f6475fdcb3c28ff3c55cc4b7bde632119ec08"},{"url":"https://git.kernel.org/stable/c/0417adf367a0af11adf7ace849af4638cfb573f7"}],"tags":["cve.org"],"epss":0.00308,"epssPercentile":0.23496,"ingestedAt":"2026-10-15T22:48:25.519Z","slug":"CVE-2025-39673","body":"## Overview\n\nIn the Linux kernel, the following vulnerability has been resolved:\n\nppp: fix race conditions in ppp_fill_forward_path\n\nppp_fill_forward_path() has two race conditions:\n\n1. The ppp->channels list can change between list_empty() and\n   list_first_entry(), as ppp_lock() is not held. If the only channel\n   is deleted in ppp_disconnect_channel(), list_first_entry() may\n   access an empty head or a freed entry, and trigger a panic.\n\n2. pch->chan can be NULL. When ppp_unregister_channel() is called,\n   pch->chan is set to NULL before pch is removed from ppp->channels.\n\nFix these by using a lockless RCU approach:\n- Use list_first_or_null_rcu() to safely test and access the first list\n  entry.\n- Convert list modifications on ppp->channels to their RCU variants and\n  add synchronize_net() after removal.\n- Check for a NULL pch->chan before dereferencing it.\n\n## Affected\n\n- `Linux >= f6efc675c9dd8d93f826b79ae7e33e03301db609 < 9a1969fbffc1f1900d92d7594b1b7d8d72ef3dc7`\n- `Linux >= f6efc675c9dd8d93f826b79ae7e33e03301db609 < 0f1630be6fcca3f0c63e4b242ad202e5cde28a40`\n- `Linux >= f6efc675c9dd8d93f826b79ae7e33e03301db609 < ca18d751bcc9faf5b7e82e9fae1223d103928181`\n- `Linux >= f6efc675c9dd8d93f826b79ae7e33e03301db609 < 94731cc551e29511d85aa8dec61a6c071b1f2430`\n- `Linux >= f6efc675c9dd8d93f826b79ae7e33e03301db609 < f97f6475fdcb3c28ff3c55cc4b7bde632119ec08`\n- `Linux >= f6efc675c9dd8d93f826b79ae7e33e03301db609 < 0417adf367a0af11adf7ace849af4638cfb573f7`\n- `Linux 5.13`\n\n## Remediation\n\nRefer to the linked advisories for vendor-supplied fixes and affected version ranges.","depth":"midnight","depthScore":54,"depthScoreParts":{"impact":53.9,"likelihood":0.1,"exploitation":0,"ransomware":0},"changes":[]}