{"cve":"CVE-2026-52980","nvd":{"published":"2026-06-24T17:17:08.610","modified":"2026-07-14T16:51:26.420","status":"Analyzed","description":"In the Linux kernel, the following vulnerability has been resolved:\n\nsched/fair: Clear rel_deadline when initializing forked entities\n\nA yield-triggered crash can happen when a newly forked sched_entity\nenters the fair class with se->rel_deadline unexpectedly set.\n\nThe failing sequence is:\n\n  1. A task is forked while se->rel_deadline is still set.\n  2. __sched_fork() initializes vruntime, vlag and other sched_entity\n     state, but does not clear rel_deadline.\n  3. On the first enqueue, enqueue_entity() calls place_entity().\n  4. Because se->rel_deadline is set, place_entity() treats se->deadline\n     as a relative deadline and converts it to an absolute deadline by\n     adding the current vruntime.\n  5. However, the forked entity's deadline is not a valid inherited\n     relative deadline for this new scheduling instance, so the conversion\n     produces an abnormally large deadline.\n  6. If the task later calls sched_yield(), yield_task_fair() advances\n     se->vruntime to se->deadline.\n  7. The inflated vruntime is then used by the following enqueue path,\n     where the vruntime-derived key can overflow when multiplied by the\n     entity weight.\n  8. This corrupts cfs_rq->sum_w_vruntime, breaks EEVDF eligibility\n     calculation, and can eventually make all entities appear ineligible.\n     pick_next_entity() may then return NULL unexpectedly, leading to a\n     later NULL dereference.\n\nA captured trace shows the effect clearly. Before yield, the entity's\nvruntime was around:\n\n  9834017729983308\n\nAfter yield_task_fair() executed:\n\n  se->vruntime = se->deadline\n\nthe vruntime jumped to:\n\n  19668035460670230\n\nand the deadline was later advanced further to:\n\n  19668035463470230\n\nThis shows that the deadline had already become abnormally large before\nyield_task_fair() copied it into vruntime.\n\nrel_deadline is only meaningful when se->deadline really carries a\nrelative deadline that still needs to be placed against vruntime. A\nfreshly forked sched_entity should not inherit or retain this state.\nClear se->rel_deadline in __sched_fork(), together with the other\nsched_entity runtime state, so that the first enqueue does not interpret\nthe new entity's deadline as a stale relative deadline.","cvss_v4":null,"cvss_v3":{"version":"3.1","vector":"CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H","score":5.5},"cwes":["CWE-476"],"references":["https://git.kernel.org/stable/c/3da56dc063cd77b9c0b40add930767fab4e389f3","https://git.kernel.org/stable/c/8f4a16200785f49cf02c5b71bdfe7a9dab63f23a","https://git.kernel.org/stable/c/c71bf35caba12bfd9bc23e32b0bcd9e02d1cf1ac","https://git.kernel.org/stable/c/f3c16e1f4a314a20717ab90a41885f8111a242ab"],"products":["linux:linux_kernel"],"source":"nvd","synced_at":"2026-10-19T22:41:17.107060303+00:00"},"epss":{"cve":"CVE-2026-52980","score":0.00162,"percentile":0.05343,"date":"2026-10-31"},"kev":null,"osv":[],"attribution":["This product uses the NVD API but is not endorsed or certified by the NVD.","EPSS scores: FIRST Exploit Prediction Scoring System, https://www.first.org/epss","Known exploited vulnerabilities: CISA Known Exploited Vulnerabilities Catalog, https://www.cisa.gov/known-exploited-vulnerabilities-catalog","Package advisories: OSV (https://osv.dev), from the GitHub Advisory Database, PyPA, Go, RustSec and other ecosystem databases, under CC-BY 4.0 or CC0","CVE records: the CVE Program's CVE List (https://www.cve.org), under its terms of use (https://www.cve.org/Legal/TermsOfUse). CVE is a registered trademark of The MITRE Corporation; this product is not affiliated with the CVE Program."]}