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Exploitation unknown; this catalogue does not assess exploitation. ## Source facts (JSON-quoted data) CNA source text (English) id: "CVE-2025-39915" idYear: 2025 status: "PUBLISHED" publishedAt: "2025-10-01T07:44:37.884Z" updatedAt: "2026-05-11T21:38:52.462Z" importedAt: "2026-10-24T01:57:34.152Z" snapshot: {"id":"cve_2026-10-24_midnight_baseline","at":"2026-10-24T00:00:00.000Z","source":"https://github.com/CVEProject/cvelistV5/releases/tag/cve_2026-10-24_0100Z"} url: "https://cveboard.org/cve/CVE-2025-39915" json: "https://cveboard.org/cve/CVE-2025-39915.json" sourceURL: "https://www.cve.org/CVERecord?id=CVE-2025-39915" title: "net: phy: transfer phy_config_inband() locking responsibility to phylink" summary: "In the Linux kernel, the following vulnerability has been resolved:\n\nnet: phy: transfer phy_config_inband() locking responsibility to phylink\n\nProblem description\n===================\n\nLockdep reports a possible circular locking dependency (AB/BA) between\n&pl-\u003estate_mutex and &phy-\u003elock, as follows.\n\nphylink_resolve() // acquires &pl-\u003estate_mutex\n-\u003e phylink_major_config()\n -\u003e phy_config_inband() // acquires &pl-\u003ephydev-\u003elock\n\nwhereas all the other call sites where &pl-\u003estate_mutex and\n&pl-\u003ephydev-\u003elock have the locking scheme reversed. Everywhere else,\n&pl-\u003ephydev-\u003elock is acquired at the top level, and &pl-\u003estate_mutex at\nthe lower level. A clear example is phylink_bringup_phy().\n\nThe outlier is the newly introduced phy_config_inband() and the existing\nlock order is the correct one. To understand why it cannot be the other\nway around, it is sufficient to consider phylink_phy_change(), phylink's\ncallback from the PHY device's phy-\u003ephy_link_change() virtual method,\ninvoked by the PHY state machine.\n\nphy_link_up() and phy_link_down(), the (indirect) callers of\nphylink_phy_change(), are called with &phydev-\u003elock acquired.\nThen phylink_phy_change() acquires its own &pl-\u003estate_mutex, to\nserialize changes made to its pl-\u003ephy_state and pl-\u003elink_config.\nSo all other instances of &pl-\u003estate_mutex and &phydev-\u003elock must be\nconsistent with this order.\n\nProblem impact\n==============\n\nI think the kernel runs a serious deadlock risk if an existing\nphylink_resolve() thread, which results in a phy_config_inband() call,\nis concurrent with a phy_link_up() or phy_link_down() call, which will\ndeadlock on &pl-\u003estate_mutex in phylink_phy_change(). Practically\nspeaking, the impact may be limited by the slow speed of the medium\nauto-negotiation protocol, which makes it unlikely for the current state\nto still be unresolved when a new one is detected, but I think the\nproblem is there. Nonetheless, the problem was discovered using lockdep.\n\nProposed solution\n=================\n\nPractically speaking, the phy_config_inband() requirement of having\nphydev-\u003elock acquired must transfer to the caller (phylink is the only\ncaller). There, it must bubble up until immediately before\n&pl-\u003estate_mutex is acquired, for the cases where that takes place.\n\nSolution details, considerations, notes\n=======================================\n\nThis is the phy_config_inband() call graph:\n\n sfp_upstream_ops :: connect_phy()\n |\n v\n phylink_sfp_connect_phy()\n |\n v\n phylink_sfp_config_phy()\n |\n | sfp_upstream_ops :: module_insert()\n | |\n | v\n | phylink_sfp_module_insert()\n | |\n | | sfp_upstream_ops :: module_start()\n | | |\n | | v\n | | phylink_sfp_module_start()\n | | |\n | v v\n | phylink_sfp_config_optical()\n phylink_start() | |\n | phylink_resume() v v\n | | phylink_sfp_set_config()\n | | |\n v v v\n phylink_mac_initial_config()\n | phylink_resolve()\n | | phylink_ethtool_ksettings_set()\n v v v\n phylink_major_config()\n |\n v\n phy_config_inband()\n\nphylink_major_config() caller #1, phylink_mac_initial_config(), does not\nacquire &pl-\u003estate_mutex nor do its callers. It must acquire\n&pl-\u003ephydev-\u003elock prior to calling phylink_major_config().\n\nphylink_major_config() caller #2, phylink_resolve() acquires\n&pl-\u003estate_mutex, thus also needs to acquire &pl-\u003ephydev-\u003elock.\n\nphylink_major_config() caller #3, phylink_ethtool_ksettings_set(), is\ncompletely uninteresting, because it only call\n---truncated---" affected: [{"versions":[{"version":"5fd0f1a02e750e2db4038dee60edea669ce5aab1","status":"affected","versionType":"git","lessThan":"052ac41c379c8b87629808be612a482b2d0ae283"},{"version":"5fd0f1a02e750e2db4038dee60edea669ce5aab1","status":"affected","versionType":"git","lessThan":"e2a10daba84968f6b5777d150985fd7d6abc9c84"}],"vendor":"Linux","product":"Linux","defaultStatus":"unaffected"},{"versions":[{"version":"6.14","status":"affected"},{"version":"0","status":"unaffected","versionType":"semver","lessThan":"6.14"},{"version":"6.16.8","status":"unaffected","versionType":"semver","lessThanOrEqual":"6.16.*"},{"version":"6.17","status":"unaffected","versionType":"original_commit_for_fix","lessThanOrEqual":"*"}],"vendor":"Linux","product":"Linux","defaultStatus":"affected"}] ## Source licences and attribution CISA Known Exploited Vulnerabilities: https://www.cisa.gov/known-exploited-vulnerabilities-catalog (US government work) GitHub Advisory Database: https://github.com/advisories (CC BY 4.0) Have I Been Pwned: https://haveibeenpwned.com/ (CC BY 4.0) CVE Program (CVE records): https://www.cve.org/Legal/TermsOfUse (CVE Terms of Use) Copyright © 1999-2026, The MITRE Corporation. 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