{"id":"CVE-2025-39877","title":"mm/damon/sysfs: fix use-after-free in state_show()","summary":"In the Linux kernel, the following vulnerability has been resolved:\n\nmm/damon/sysfs: fix use-after-free in state_show()\n\nstate_show() reads kdamond->damon_ctx without holding damon_sysfs_lock. \nThis allows a use-after-free race:\n\nCPU 0  …","severity":"none","vendor":"Linux","product":"Linux","affected":["Linux >= a61ea561c87139992fe32afdee48a6f6b85d824a < 3858c44341ad49dc7544b19cc9f9ecffaa7cc50e","Linux >= a61ea561c87139992fe32afdee48a6f6b85d824a < 60d7a3d2b985a395318faa1d88da6915fad11c19","Linux >= a61ea561c87139992fe32afdee48a6f6b85d824a < 26d29b2ac87a2989071755f9828ebf839b560d4c","Linux >= a61ea561c87139992fe32afdee48a6f6b85d824a < 4e87f461d61959647464a94d11ae15c011be58ce","Linux >= a61ea561c87139992fe32afdee48a6f6b85d824a < 3260a3f0828e06f5f13fac69fb1999a6d60d9cff","Linux 5.18"],"ssvc":{"exploitation":"none","automatable":"no","technicalImpact":"partial","timestamp":"2026-11-05T21:12:49.483083Z"},"published":"2025-09-23","updated":"2026-11-05","sourceUpdated":"2026-11-05T21:23:06.295Z","source":"CVEORG","sourceUrl":"https://www.cve.org/CVERecord?id=CVE-2025-39877","references":[{"url":"https://git.kernel.org/stable/c/3858c44341ad49dc7544b19cc9f9ecffaa7cc50e"},{"url":"https://git.kernel.org/stable/c/60d7a3d2b985a395318faa1d88da6915fad11c19"},{"url":"https://git.kernel.org/stable/c/26d29b2ac87a2989071755f9828ebf839b560d4c"},{"url":"https://git.kernel.org/stable/c/4e87f461d61959647464a94d11ae15c011be58ce"},{"url":"https://git.kernel.org/stable/c/3260a3f0828e06f5f13fac69fb1999a6d60d9cff"}],"tags":["cve.org"],"epss":0.00154,"epssPercentile":0.04518,"ingestedAt":"2026-11-05T22:38:32.045Z","slug":"CVE-2025-39877","body":"## Overview\n\nIn the Linux kernel, the following vulnerability has been resolved:\n\nmm/damon/sysfs: fix use-after-free in state_show()\n\nstate_show() reads kdamond->damon_ctx without holding damon_sysfs_lock. \nThis allows a use-after-free race:\n\nCPU 0                         CPU 1\n-----                         -----\nstate_show()                  damon_sysfs_turn_damon_on()\nctx = kdamond->damon_ctx;     mutex_lock(&damon_sysfs_lock);\n                              damon_destroy_ctx(kdamond->damon_ctx);\n                              kdamond->damon_ctx = NULL;\n                              mutex_unlock(&damon_sysfs_lock);\ndamon_is_running(ctx);        /* ctx is freed */\nmutex_lock(&ctx->kdamond_lock); /* UAF */\n\n(The race can also occur with damon_sysfs_kdamonds_rm_dirs() and\ndamon_sysfs_kdamond_release(), which free or replace the context under\ndamon_sysfs_lock.)\n\nFix by taking damon_sysfs_lock before dereferencing the context, mirroring\nthe locking used in pid_show().\n\nThe bug has existed since state_show() first accessed kdamond->damon_ctx.\n\n## Affected\n\n- `Linux >= a61ea561c87139992fe32afdee48a6f6b85d824a < 3858c44341ad49dc7544b19cc9f9ecffaa7cc50e`\n- `Linux >= a61ea561c87139992fe32afdee48a6f6b85d824a < 60d7a3d2b985a395318faa1d88da6915fad11c19`\n- `Linux >= a61ea561c87139992fe32afdee48a6f6b85d824a < 26d29b2ac87a2989071755f9828ebf839b560d4c`\n- `Linux >= a61ea561c87139992fe32afdee48a6f6b85d824a < 4e87f461d61959647464a94d11ae15c011be58ce`\n- `Linux >= a61ea561c87139992fe32afdee48a6f6b85d824a < 3260a3f0828e06f5f13fac69fb1999a6d60d9cff`\n- `Linux 5.18`\n\n## Remediation\n\nRefer to the linked advisories for vendor-supplied fixes and affected version ranges.","depth":"sunlit","depthScore":3,"depthScoreParts":{"impact":2.8,"likelihood":0,"exploitation":0,"ransomware":0},"changes":[]}