{"dataType": "CVE_RECORD", "dataVersion": "5.2", "cveMetadata": {"cveId": "CVE-2025-39881", "assignerOrgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "state": "PUBLISHED", "assignerShortName": "Linux", "dateReserved": "2025-04-16T07:20:57.144Z", "datePublished": "2025-09-23T06:00:50.496Z", "dateUpdated": "2025-11-03T17:44:23.968Z"}, "containers": {"cna": {"providerMetadata": {"orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "shortName": "Linux", "dateUpdated": "2025-09-29T06:01:40.892Z"}, "descriptions": [{"lang": "en", "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nkernfs: Fix UAF in polling when open file is released\n\nA use-after-free (UAF) vulnerability was identified in the PSI (Pressure\nStall Information) monitoring mechanism:\n\nBUG: KASAN: slab-use-after-free in psi_trigger_poll+0x3c/0x140\nRead of size 8 at addr ffff3de3d50bd308 by task systemd/1\n\npsi_trigger_poll+0x3c/0x140\ncgroup_pressure_poll+0x70/0xa0\ncgroup_file_poll+0x8c/0x100\nkernfs_fop_poll+0x11c/0x1c0\nep_item_poll.isra.0+0x188/0x2c0\n\nAllocated by task 1:\ncgroup_file_open+0x88/0x388\nkernfs_fop_open+0x73c/0xaf0\ndo_dentry_open+0x5fc/0x1200\nvfs_open+0xa0/0x3f0\ndo_open+0x7e8/0xd08\npath_openat+0x2fc/0x6b0\ndo_filp_open+0x174/0x368\n\nFreed by task 8462:\ncgroup_file_release+0x130/0x1f8\nkernfs_drain_open_files+0x17c/0x440\nkernfs_drain+0x2dc/0x360\nkernfs_show+0x1b8/0x288\ncgroup_file_show+0x150/0x268\ncgroup_pressure_write+0x1dc/0x340\ncgroup_file_write+0x274/0x548\n\nReproduction Steps:\n1. Open test/cpu.pressure and establish epoll monitoring\n2. Disable monitoring: echo 0 > test/cgroup.pressure\n3. Re-enable monitoring: echo 1 > test/cgroup.pressure\n\nThe race condition occurs because:\n1. When cgroup.pressure is disabled (echo 0 > cgroup.pressure), it:\n - Releases PSI triggers via cgroup_file_release()\n - Frees of->priv through kernfs_drain_open_files()\n2. While epoll still holds reference to the file and continues polling\n3. Re-enabling (echo 1 > cgroup.pressure) accesses freed of->priv\n\nepolling\t\t\tdisable/enable cgroup.pressure\nfd=open(cpu.pressure)\nwhile(1)\n...\nepoll_wait\nkernfs_fop_poll\nkernfs_get_active = true\techo 0 > cgroup.pressure\n...\t\t\t\tcgroup_file_show\n\t\t\t\tkernfs_show\n\t\t\t\t// inactive kn\n\t\t\t\tkernfs_drain_open_files\n\t\t\t\tcft->release(of);\n\t\t\t\tkfree(ctx);\n\t\t\t\t...\nkernfs_get_active = false\n\t\t\t\techo 1 > cgroup.pressure\n\t\t\t\tkernfs_show\n\t\t\t\tkernfs_activate_one(kn);\nkernfs_fop_poll\nkernfs_get_active = true\ncgroup_file_poll\npsi_trigger_poll\n// UAF\n...\nend: close(fd)\n\nTo address this issue, introduce kernfs_get_active_of() for kernfs open\nfiles to obtain active references. This function will fail if the open file\nhas been released. Replace kernfs_get_active() with kernfs_get_active_of()\nto prevent further operations on released file descriptors."}], "affected": [{"product": "Linux", "vendor": "Linux", "defaultStatus": "unaffected", "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git", "programFiles": ["fs/kernfs/file.c"], "versions": [{"version": "34f26a15611afb03c33df6819359d36f5b382589", "lessThan": "34d9cafd469c69ad85e6a36b4303c78382cf5c79", "status": "affected", "versionType": "git"}, {"version": "34f26a15611afb03c33df6819359d36f5b382589", "lessThan": "854baafc00c433cccbe0ab4231b77aeb9b637b77", "status": "affected", "versionType": "git"}, {"version": "34f26a15611afb03c33df6819359d36f5b382589", "lessThan": "7e64474aba78d240f7804f48f2d454dcca78b15f", "status": "affected", "versionType": "git"}, {"version": "34f26a15611afb03c33df6819359d36f5b382589", "lessThan": "ac5cda4fae8818cf1963317bb699f7f2f85b60af", "status": "affected", "versionType": "git"}, {"version": "34f26a15611afb03c33df6819359d36f5b382589", "lessThan": "3c9ba2777d6c86025e1ba4186dc5cd930e40ec5f", "status": "affected", "versionType": "git"}]}, {"product": "Linux", "vendor": "Linux", "defaultStatus": "affected", "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git", "programFiles": ["fs/kernfs/file.c"], "versions": [{"version": "6.1", "status": "affected"}, {"version": "0", "lessThan": "6.1", "status": "unaffected", "versionType": "semver"}, {"version": "6.1.153", "lessThanOrEqual": "6.1.*", "status": "unaffected", "versionType": "semver"}, {"version": "6.6.107", "lessThanOrEqual": "6.6.*", "status": "unaffected", "versionType": "semver"}, {"version": "6.12.48", "lessThanOrEqual": "6.12.*", "status": "unaffected", "versionType": "semver"}, {"version": "6.16.8", "lessThanOrEqual": "6.16.*", "status": "unaffected", "versionType": "semver"}, {"version": "6.17", "lessThanOrEqual": "*", "status": "unaffected", "versionType": "original_commit_for_fix"}]}], "cpeApplicability": [{"nodes": [{"operator": "OR", "negate": false, "cpeMatch": [{"vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "6.1", "versionEndExcluding": "6.1.153"}, {"vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "6.1", "versionEndExcluding": "6.6.107"}, {"vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "6.1", "versionEndExcluding": "6.12.48"}, {"vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "6.1", "versionEndExcluding": "6.16.8"}, {"vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "6.1", "versionEndExcluding": "6.17"}]}]}], "references": [{"url": "https://git.kernel.org/stable/c/34d9cafd469c69ad85e6a36b4303c78382cf5c79"}, {"url": "https://git.kernel.org/stable/c/854baafc00c433cccbe0ab4231b77aeb9b637b77"}, {"url": "https://git.kernel.org/stable/c/7e64474aba78d240f7804f48f2d454dcca78b15f"}, {"url": "https://git.kernel.org/stable/c/ac5cda4fae8818cf1963317bb699f7f2f85b60af"}, {"url": "https://git.kernel.org/stable/c/3c9ba2777d6c86025e1ba4186dc5cd930e40ec5f"}], "title": "kernfs: Fix UAF in polling when open file is released", "x_generator": {"engine": "bippy-1.2.0"}}, "adp": [{"title": "CVE Program Container", "references": [{"url": "https://lists.debian.org/debian-lts-announce/2025/10/msg00008.html"}], "providerMetadata": {"orgId": "af854a3a-2127-422b-91ae-364da2661108", "shortName": "CVE", "dateUpdated": "2025-11-03T17:44:23.968Z"}}]}}

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Open test/cpu.pressure and establish epoll monitoring\n2. Disable monitoring: echo 0 > test/cgroup.pressure\n3. Re-enable monitoring: echo 1 > test/cgroup.pressure\n\nThe race condition occurs because:\n1. When cgroup.pressure is disabled (echo 0 > cgroup.pressure), it:\n - Releases PSI triggers via cgroup_file_release()\n - Frees of->priv through kernfs_drain_open_files()\n2. While epoll still holds reference to the file and continues polling\n3. Re-enabling (echo 1 > cgroup.pressure) accesses freed of->priv\n\nepolling\t\t\tdisable/enable cgroup.pressure\nfd=open(cpu.pressure)\nwhile(1)\n...\nepoll_wait\nkernfs_fop_poll\nkernfs_get_active = true\techo 0 > cgroup.pressure\n...\t\t\t\tcgroup_file_show\n\t\t\t\tkernfs_show\n\t\t\t\t// inactive kn\n\t\t\t\tkernfs_drain_open_files\n\t\t\t\tcft->release(of);\n\t\t\t\tkfree(ctx);\n\t\t\t\t...\nkernfs_get_active = false\n\t\t\t\techo 1 > cgroup.pressure\n\t\t\t\tkernfs_show\n\t\t\t\tkernfs_activate_one(kn);\nkernfs_fop_poll\nkernfs_get_active = true\ncgroup_file_poll\npsi_trigger_poll\n// UAF\n...\nend: close(fd)\n\nTo address this issue, introduce kernfs_get_active_of() for kernfs open\nfiles to obtain active references. This function will fail if the open file\nhas been released. Replace kernfs_get_active() with kernfs_get_active_of()\nto prevent further operations on released file descriptors."}], "id": "CVE-2025-39881", "lastModified": "2026-01-16T19:26:01.513", "metrics": {"cvssMetricV31": [{"cvssData": {"attackComplexity": "LOW", "attackVector": "LOCAL", "availabilityImpact": "HIGH", "baseScore": 7.8, "baseSeverity": "HIGH", "confidentialityImpact": "HIGH", "integrityImpact": "HIGH", "privilegesRequired": "LOW", "scope": "UNCHANGED", "userInteraction": "NONE", "vectorString": "CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H", "version": "3.1"}, "exploitabilityScore": 1.8, "impactScore": 5.9, "source": "nvd@nist.gov", "type": "Primary"}]}, "published": "2025-09-23T06:15:47.793", "references": [{"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "tags": ["Patch"], "url": "https://git.kernel.org/stable/c/34d9cafd469c69ad85e6a36b4303c78382cf5c79"}, {"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "tags": ["Patch"], "url": "https://git.kernel.org/stable/c/3c9ba2777d6c86025e1ba4186dc5cd930e40ec5f"}, {"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "tags": ["Patch"], "url": "https://git.kernel.org/stable/c/7e64474aba78d240f7804f48f2d454dcca78b15f"}, {"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "tags": ["Patch"], "url": "https://git.kernel.org/stable/c/854baafc00c433cccbe0ab4231b77aeb9b637b77"}, {"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "tags": ["Patch"], "url": "https://git.kernel.org/stable/c/ac5cda4fae8818cf1963317bb699f7f2f85b60af"}, {"source": "af854a3a-2127-422b-91ae-364da2661108", "tags": ["Third Party Advisory"], "url": "https://lists.debian.org/debian-lts-announce/2025/10/msg00008.html"}], "sourceIdentifier": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "vulnStatus": "Analyzed", "weaknesses": [{"description": [{"lang": "en", "value": "CWE-416"}], "source": "nvd@nist.gov", "type": "Primary"}]}

{"bugzilla": {"description": "kernel: kernfs: Fix UAF in polling when open file is released", "id": "2397558", "url": "https://bugzilla.redhat.com/show_bug.cgi?id=2397558"}, "csaw": false, "cvss3": {"cvss3_base_score": "7.0", "cvss3_scoring_vector": "CVSS:3.1/AV:L/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:H", "status": "draft"}, "details": ["No description is available for this CVE."], "name": "CVE-2025-39881", "package_state": [{"cpe": "cpe:/o:redhat:enterprise_linux:10", "fix_state": "Affected", "package_name": "kernel", "product_name": "Red Hat Enterprise Linux 10"}, {"cpe": "cpe:/o:redhat:enterprise_linux:6", "fix_state": "Not affected", "package_name": "kernel", "product_name": "Red Hat Enterprise Linux 6"}, {"cpe": "cpe:/o:redhat:enterprise_linux:7", "fix_state": "Not affected", "package_name": "kernel", "product_name": "Red Hat Enterprise Linux 7"}, {"cpe": "cpe:/o:redhat:enterprise_linux:7", "fix_state": "Not affected", "package_name": "kernel-rt", "product_name": "Red Hat Enterprise Linux 7"}, {"cpe": "cpe:/o:redhat:enterprise_linux:8", "fix_state": "Not affected", "package_name": "kernel", "product_name": "Red Hat Enterprise Linux 8"}, {"cpe": "cpe:/o:redhat:enterprise_linux:8", "fix_state": "Not affected", "package_name": "kernel-rt", "product_name": "Red Hat Enterprise Linux 8"}, {"cpe": "cpe:/o:redhat:enterprise_linux:9", "fix_state": "Affected", "package_name": "kernel", "product_name": "Red Hat Enterprise Linux 9"}, {"cpe": "cpe:/o:redhat:enterprise_linux:9", "fix_state": "Affected", "package_name": "kernel-rt", "product_name": "Red Hat Enterprise Linux 9"}], "public_date": "2025-09-23T00:00:00Z", "references": ["https://www.cve.org/CVERecord?id=CVE-2025-39881\nhttps://nvd.nist.gov/vuln/detail/CVE-2025-39881\nhttps://lore.kernel.org/linux-cve-announce/2025092301-CVE-2025-39881-a4e1@gregkh/T"], "threat_severity": "Moderate"}

{"created": "2025-09-23T16:03:18.565528+00:00", "updated": "2025-09-23T16:03:18.565610+00:00", "vendors": ["linux", "linux$PRODUCT$linux_kernel"]}