{"dataType": "CVE_RECORD", "dataVersion": "5.2", "cveMetadata": {"cveId": "CVE-2025-39821", "assignerOrgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "state": "PUBLISHED", "assignerShortName": "Linux", "dateReserved": "2025-04-16T07:20:57.139Z", "datePublished": "2025-09-16T13:00:20.805Z", "dateUpdated": "2026-01-14T18:22:56.192Z"}, "containers": {"cna": {"providerMetadata": {"orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "shortName": "Linux", "dateUpdated": "2025-09-29T06:00:21.008Z"}, "descriptions": [{"lang": "en", "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nperf: Avoid undefined behavior from stopping/starting inactive events\n\nCalling pmu->start()/stop() on perf events in PERF_EVENT_STATE_OFF can\nleave event->hw.idx at -1. When PMU drivers later attempt to use this\nnegative index as a shift exponent in bitwise operations, it leads to UBSAN\nshift-out-of-bounds reports.\n\nThe issue is a logical flaw in how event groups handle throttling when some\nmembers are intentionally disabled. Based on the analysis and the\nreproducer provided by Mark Rutland (this issue on both arm64 and x86-64).\n\nThe scenario unfolds as follows:\n\n 1. A group leader event is configured with a very aggressive sampling\n period (e.g., sample_period = 1). This causes frequent interrupts and\n triggers the throttling mechanism.\n 2. A child event in the same group is created in a disabled state\n (.disabled = 1). This event remains in PERF_EVENT_STATE_OFF.\n Since it hasn't been scheduled onto the PMU, its event->hw.idx remains\n initialized at -1.\n 3. When throttling occurs, perf_event_throttle_group() and later\n perf_event_unthrottle_group() iterate through all siblings, including\n the disabled child event.\n 4. perf_event_throttle()/unthrottle() are called on this inactive child\n event, which then call event->pmu->start()/stop().\n 5. The PMU driver receives the event with hw.idx == -1 and attempts to\n use it as a shift exponent. e.g., in macros like PMCNTENSET(idx),\n leading to the UBSAN report.\n\nThe throttling mechanism attempts to start/stop events that are not\nactively scheduled on the hardware.\n\nMove the state check into perf_event_throttle()/perf_event_unthrottle() so\nthat inactive events are skipped entirely. This ensures only active events\nwith a valid hw.idx are processed, preventing undefined behavior and\nsilencing UBSAN warnings. The corrected check ensures true before\nproceeding with PMU operations.\n\nThe problem can be reproduced with the syzkaller reproducer:"}], "affected": [{"product": "Linux", "vendor": "Linux", "defaultStatus": "unaffected", "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git", "programFiles": ["kernel/events/core.c"], "versions": [{"version": "9734e25fbf5ae68eb04234b2cd14a4b36ab89141", "lessThan": "d689135aa9c5e4e0eab5a92bbe35dab0c8d6677f", "status": "affected", "versionType": "git"}, {"version": "9734e25fbf5ae68eb04234b2cd14a4b36ab89141", "lessThan": "b64fdd422a85025b5e91ead794db9d3ef970e369", "status": "affected", "versionType": "git"}]}, {"product": "Linux", "vendor": "Linux", "defaultStatus": "affected", "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git", "programFiles": ["kernel/events/core.c"], "versions": [{"version": "6.16", "status": "affected"}, {"version": "0", "lessThan": "6.16", "status": "unaffected", "versionType": "semver"}, {"version": "6.16.5", "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": "6.16", "versionEndExcluding": "6.16.5"}, {"vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "6.16", "versionEndExcluding": "6.17"}]}]}], "references": [{"url": "https://git.kernel.org/stable/c/d689135aa9c5e4e0eab5a92bbe35dab0c8d6677f"}, {"url": "https://git.kernel.org/stable/c/b64fdd422a85025b5e91ead794db9d3ef970e369"}], "title": "perf: Avoid undefined behavior from stopping/starting inactive events", "x_generator": {"engine": "bippy-1.2.0"}}, "adp": [{"metrics": [{"cvssV3_1": {"scope": "UNCHANGED", "version": "3.1", "baseScore": 7.8, "attackVector": "LOCAL", "baseSeverity": "HIGH", "vectorString": "CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H", "integrityImpact": "HIGH", "userInteraction": "NONE", "attackComplexity": "LOW", "availabilityImpact": "HIGH", "privilegesRequired": "LOW", "confidentialityImpact": "HIGH"}}, {"other": {"type": "ssvc", "content": {"id": "CVE-2025-39821", "role": "CISA Coordinator", "options": [{"Exploitation": "none"}, {"Automatable": "no"}, {"Technical Impact": "total"}], "version": "2.0.3", "timestamp": "2026-01-14T18:16:47.835074Z"}}}], "problemTypes": [{"descriptions": [{"lang": "en", "type": "CWE", "cweId": "CWE-787", "description": "CWE-787 Out-of-bounds Write"}]}], "title": "CISA ADP Vulnrichment", "providerMetadata": {"orgId": "134c704f-9b21-4f2e-91b3-4a467353bcc0", "shortName": "CISA-ADP", "dateUpdated": "2026-01-14T18:22:56.192Z"}}]}}

{"dataType": "CVE_RECORD", "dataVersion": "5.1", "cveMetadata": {"cveId": "CVE-2025-39821", "assignerOrgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "state": "PUBLISHED", "assignerShortName": "Linux", "dateReserved": "2025-04-16T07:20:57.139Z", "datePublished": "2025-09-16T13:00:20.805Z", "dateUpdated": "2025-09-29T06:00:21.008Z"}, "containers": {"cna": {"providerMetadata": {"orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "shortName": "Linux", "dateUpdated": "2025-09-29T06:00:21.008Z"}, "descriptions": [{"lang": "en", "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nperf: Avoid undefined behavior from stopping/starting inactive events\n\nCalling pmu->start()/stop() on perf events in PERF_EVENT_STATE_OFF can\nleave event->hw.idx at -1. When PMU drivers later attempt to use this\nnegative index as a shift exponent in bitwise operations, it leads to UBSAN\nshift-out-of-bounds reports.\n\nThe issue is a logical flaw in how event groups handle throttling when some\nmembers are intentionally disabled. Based on the analysis and the\nreproducer provided by Mark Rutland (this issue on both arm64 and x86-64).\n\nThe scenario unfolds as follows:\n\n 1. A group leader event is configured with a very aggressive sampling\n period (e.g., sample_period = 1). This causes frequent interrupts and\n triggers the throttling mechanism.\n 2. A child event in the same group is created in a disabled state\n (.disabled = 1). This event remains in PERF_EVENT_STATE_OFF.\n Since it hasn't been scheduled onto the PMU, its event->hw.idx remains\n initialized at -1.\n 3. When throttling occurs, perf_event_throttle_group() and later\n perf_event_unthrottle_group() iterate through all siblings, including\n the disabled child event.\n 4. perf_event_throttle()/unthrottle() are called on this inactive child\n event, which then call event->pmu->start()/stop().\n 5. The PMU driver receives the event with hw.idx == -1 and attempts to\n use it as a shift exponent. e.g., in macros like PMCNTENSET(idx),\n leading to the UBSAN report.\n\nThe throttling mechanism attempts to start/stop events that are not\nactively scheduled on the hardware.\n\nMove the state check into perf_event_throttle()/perf_event_unthrottle() so\nthat inactive events are skipped entirely. This ensures only active events\nwith a valid hw.idx are processed, preventing undefined behavior and\nsilencing UBSAN warnings. The corrected check ensures true before\nproceeding with PMU operations.\n\nThe problem can be reproduced with the syzkaller reproducer:"}], "affected": [{"product": "Linux", "vendor": "Linux", "defaultStatus": "unaffected", "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git", "programFiles": ["kernel/events/core.c"], "versions": [{"version": "9734e25fbf5ae68eb04234b2cd14a4b36ab89141", "lessThan": "d689135aa9c5e4e0eab5a92bbe35dab0c8d6677f", "status": "affected", "versionType": "git"}, {"version": "9734e25fbf5ae68eb04234b2cd14a4b36ab89141", "lessThan": "b64fdd422a85025b5e91ead794db9d3ef970e369", "status": "affected", "versionType": "git"}]}, {"product": "Linux", "vendor": "Linux", "defaultStatus": "affected", "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git", "programFiles": ["kernel/events/core.c"], "versions": [{"version": "6.16", "status": "affected"}, {"version": "0", "lessThan": "6.16", "status": "unaffected", "versionType": "semver"}, {"version": "6.16.5", "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": "6.16", "versionEndExcluding": "6.16.5"}, {"vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "6.16", "versionEndExcluding": "6.17"}]}]}], "references": [{"url": "https://git.kernel.org/stable/c/d689135aa9c5e4e0eab5a92bbe35dab0c8d6677f"}, {"url": "https://git.kernel.org/stable/c/b64fdd422a85025b5e91ead794db9d3ef970e369"}], "title": "perf: Avoid undefined behavior from stopping/starting inactive events", "x_generator": {"engine": "bippy-1.2.0"}}, "adp": [{"metrics": [{"cvssV3_1": {"scope": "UNCHANGED", "version": "3.1", "baseScore": 7.8, "attackVector": "LOCAL", "baseSeverity": "HIGH", "vectorString": "CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H", "integrityImpact": "HIGH", "userInteraction": "NONE", "attackComplexity": "LOW", "availabilityImpact": "HIGH", "privilegesRequired": "LOW", "confidentialityImpact": "HIGH"}}, {"other": {"type": "ssvc", "content": {"id": "CVE-2025-39821", "role": "CISA Coordinator", "options": [{"Exploitation": "none"}, {"Automatable": "no"}, {"Technical Impact": "total"}], "version": "2.0.3", "timestamp": "2026-01-14T18:16:47.835074Z"}}}], "problemTypes": [{"descriptions": [{"lang": "en", "type": "CWE", "cweId": "CWE-787", "description": "CWE-787 Out-of-bounds Write"}]}], "providerMetadata": {"shortName": "CISA-ADP", "orgId": "134c704f-9b21-4f2e-91b3-4a467353bcc0", "dateUpdated": "2026-01-14T18:16:43.273Z"}, "title": "CISA ADP Vulnrichment"}]}}

{"configurations": [{"nodes": [{"cpeMatch": [{"criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "matchCriteriaId": "5EAC2366-3E84-4F52-AF72-DB8127DB7367", "versionEndExcluding": "6.16.5", "versionStartIncluding": "6.16", "vulnerable": true}, {"criteria": "cpe:2.3:o:linux:linux_kernel:6.17:rc1:*:*:*:*:*:*", "matchCriteriaId": "327D22EF-390B-454C-BD31-2ED23C998A1C", "vulnerable": true}, {"criteria": "cpe:2.3:o:linux:linux_kernel:6.17:rc2:*:*:*:*:*:*", "matchCriteriaId": "C730CD9A-D969-4A8E-9522-162AAF7C0EE9", "vulnerable": true}], "negate": false, "operator": "OR"}]}], "cveTags": [], "descriptions": [{"lang": "en", "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nperf: Avoid undefined behavior from stopping/starting inactive events\n\nCalling pmu->start()/stop() on perf events in PERF_EVENT_STATE_OFF can\nleave event->hw.idx at -1. When PMU drivers later attempt to use this\nnegative index as a shift exponent in bitwise operations, it leads to UBSAN\nshift-out-of-bounds reports.\n\nThe issue is a logical flaw in how event groups handle throttling when some\nmembers are intentionally disabled. Based on the analysis and the\nreproducer provided by Mark Rutland (this issue on both arm64 and x86-64).\n\nThe scenario unfolds as follows:\n\n 1. A group leader event is configured with a very aggressive sampling\n period (e.g., sample_period = 1). This causes frequent interrupts and\n triggers the throttling mechanism.\n 2. A child event in the same group is created in a disabled state\n (.disabled = 1). This event remains in PERF_EVENT_STATE_OFF.\n Since it hasn't been scheduled onto the PMU, its event->hw.idx remains\n initialized at -1.\n 3. When throttling occurs, perf_event_throttle_group() and later\n perf_event_unthrottle_group() iterate through all siblings, including\n the disabled child event.\n 4. perf_event_throttle()/unthrottle() are called on this inactive child\n event, which then call event->pmu->start()/stop().\n 5. The PMU driver receives the event with hw.idx == -1 and attempts to\n use it as a shift exponent. e.g., in macros like PMCNTENSET(idx),\n leading to the UBSAN report.\n\nThe throttling mechanism attempts to start/stop events that are not\nactively scheduled on the hardware.\n\nMove the state check into perf_event_throttle()/perf_event_unthrottle() so\nthat inactive events are skipped entirely. This ensures only active events\nwith a valid hw.idx are processed, preventing undefined behavior and\nsilencing UBSAN warnings. The corrected check ensures true before\nproceeding with PMU operations.\n\nThe problem can be reproduced with the syzkaller reproducer:"}], "id": "CVE-2025-39821", "lastModified": "2026-01-14T19:16:43.453", "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"}, {"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": "134c704f-9b21-4f2e-91b3-4a467353bcc0", "type": "Secondary"}]}, "published": "2025-09-16T13:15:59.300", "references": [{"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "tags": ["Patch"], "url": "https://git.kernel.org/stable/c/b64fdd422a85025b5e91ead794db9d3ef970e369"}, {"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "tags": ["Patch"], "url": "https://git.kernel.org/stable/c/d689135aa9c5e4e0eab5a92bbe35dab0c8d6677f"}], "sourceIdentifier": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "vulnStatus": "Modified", "weaknesses": [{"description": [{"lang": "en", "value": "CWE-787"}], "source": "nvd@nist.gov", "type": "Primary"}, {"description": [{"lang": "en", "value": "CWE-787"}], "source": "134c704f-9b21-4f2e-91b3-4a467353bcc0", "type": "Secondary"}]}

{"bugzilla": {"description": "kernel: perf: Avoid undefined behavior from stopping/starting inactive events", "id": "2395793", "url": "https://bugzilla.redhat.com/show_bug.cgi?id=2395793"}, "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-2025-39821", "package_state": [{"cpe": "cpe:/o:redhat:enterprise_linux:10", "fix_state": "Not affected", "package_name": "kernel", "product_name": "Red Hat Enterprise Linux 10"}, {"cpe": "cpe:/o:redhat:enterprise_linux:6", "fix_state": "Out of support scope", "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": "Not affected", "package_name": "kernel", "product_name": "Red Hat Enterprise Linux 9"}, {"cpe": "cpe:/o:redhat:enterprise_linux:9", "fix_state": "Not affected", "package_name": "kernel-rt", "product_name": "Red Hat Enterprise Linux 9"}], "public_date": "2025-09-16T00:00:00Z", "references": ["https://www.cve.org/CVERecord?id=CVE-2025-39821\nhttps://nvd.nist.gov/vuln/detail/CVE-2025-39821\nhttps://lore.kernel.org/linux-cve-announce/2025091616-CVE-2025-39821-3812@gregkh/T"], "threat_severity": "Moderate"}

{"created": "2025-09-17T10:04:18.193948+00:00", "updated": "2025-09-17T10:04:18.193992+00:00", "vendors": ["linux", "linux$PRODUCT$linux_kernel"]}