{"dataType":"CVE_RECORD","dataVersion":"5.2","cveMetadata":{"cveId":"CVE-2024-26737","assignerOrgId":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","state":"PUBLISHED","assignerShortName":"Linux","dateReserved":"2024-02-19T14:20:24.166Z","datePublished":"2024-04-03T17:00:23.414Z","dateUpdated":"2026-08-05T11:26:56.105Z"},"containers":{"cna":{"providerMetadata":{"orgId":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","shortName":"Linux","dateUpdated":"2026-08-05T11:26:56.105Z"},"descriptions":[{"lang":"en","value":"In the Linux kernel, the following vulnerability has been resolved:\n\nbpf: Fix racing between bpf_timer_cancel_and_free and bpf_timer_cancel\n\nThe following race is possible between bpf_timer_cancel_and_free\nand bpf_timer_cancel. It will lead a UAF on the timer->timer.\n\nbpf_timer_cancel();\n\tspin_lock();\n\tt = timer->time;\n\tspin_unlock();\n\n\t\t\t\t\tbpf_timer_cancel_and_free();\n\t\t\t\t\t\tspin_lock();\n\t\t\t\t\t\tt = timer->timer;\n\t\t\t\t\t\ttimer->timer = NULL;\n\t\t\t\t\t\tspin_unlock();\n\t\t\t\t\t\thrtimer_cancel(&t->timer);\n\t\t\t\t\t\tkfree(t);\n\n\t/* UAF on t */\n\thrtimer_cancel(&t->timer);\n\nIn bpf_timer_cancel_and_free, this patch frees the timer->timer\nafter a rcu grace period. This requires a rcu_head addition\nto the \"struct bpf_hrtimer\". Another kfree(t) happens in bpf_timer_init,\nthis does not need a kfree_rcu because it is still under the\nspin_lock and timer->timer has not been visible by others yet.\n\nIn bpf_timer_cancel, rcu_read_lock() is added because this helper\ncan be used in a non rcu critical section context (e.g. from\na sleepable bpf prog). Other timer->timer usages in helpers.c\nhave been audited, bpf_timer_cancel() is the only place where\ntimer->timer is used outside of the spin_lock.\n\nAnother solution considered is to mark a t->flag in bpf_timer_cancel\nand clear it after hrtimer_cancel() is done.  In bpf_timer_cancel_and_free,\nit busy waits for the flag to be cleared before kfree(t). This patch\ngoes with a straight forward solution and frees timer->timer after\na rcu grace period."}],"metrics":[{"cvssV3_1":{"version":"3.1","vectorString":"CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H","baseScore":7.8,"baseSeverity":"HIGH"},"scenarios":[{"lang":"en","value":"AV:L - Both sides of the race are driven through local syscalls — `bpf(BPF_PROG_LOAD)`/`BPF_PROG_TEST_RUN` to run a program calling `bpf_timer_cancel()`, and `BPF_MAP_DELETE_ELEM`/`close()` to drive `bpf_timer_cancel_and_free()`. No remotely supplied data reaches `kernel/bpf/helpers.c`, and BPF is classified as a local attack vector under kernel scoring guidance.\nAC:L - The attacker owns both racers — one thread runs its own BPF program calling `bpf_timer_cancel()` while another deletes the map element or drops the map uref — and can widen the window arbitrarily by making its own timer callback long-running, since `hrtimer_cancel()` blocks in `hrtimer_cancel_wait_running()` while the other thread finishes and `kfree()`s `t`. Nothing depends on state outside the attacker's control and the sequence can be retried in a tight loop.\nPR:L - The `bpf_timer_*` helpers are gated on `bpf_capable()` (CAP_BPF/CAP_SYS_ADMIN), a reduced non-root capability routinely delegated to unprivileged service, tracing and container workloads that are not init-namespace root. This matches this CNA's established scoring for the sibling `bpf_timer` UAFs CVE-2024-41045 and CVE-2024-42239.\nUI:N - The attacker loads its own program, arms its own timer, and issues both the cancel and the map-delete from its own threads. No victim action, mount, or interaction with any other principal is required.\nS:U - The freed `struct bpf_hrtimer` and the corrupted per-CPU hrtimer state are entirely kernel-internal, so the impact stays within the kernel's own security authority. No hypervisor, IOMMU, or sandbox boundary is crossed.\nC:H - `hrtimer_active()` reads `timer->base` out of the freed object and dereferences it (`base->seq`, `base->running`), so reclaiming the 96-byte `kmalloc-cg-96` slot with sprayed data (e.g. `msg_msg`) turns this into an attacker-directed kernel-memory read, with the helper's return value acting as an oracle. That yields arbitrary kernel data disclosure and KASLR defeat.\nI:H - After `hrtimer_active()` returns true, `lock_hrtimer_base()` takes a spinlock at an attacker-controlled address and `remove_hrtimer()`/`__remove_hrtimer()` writes `timer->state`, performs `timerqueue_del()` rb-tree unlinking and clears bits in `cpu_base->active_bases` through the same forged pointer. This is a controlled kernel write primitive suitable for privilege escalation.\nA:H - Even without a successful spray, operating on freed memory corrupts the per-CPU hrtimer queue and produces a KASAN splat, oops, or panic, and a garbage `timer->base` sends `hrtimer_cancel()` into an unterminating retry loop. The attacker can trigger this at will, repeatedly."}]}],"affected":[{"product":"Linux","vendor":"Linux","defaultStatus":"unaffected","repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["kernel/bpf/helpers.c"],"versions":[{"version":"b00628b1c7d595ae5b544e059c27b1f5828314b4","lessThan":"5268bb02107b9eedfdcd51db75b407d10043368c","status":"affected","versionType":"git"},{"version":"b00628b1c7d595ae5b544e059c27b1f5828314b4","lessThan":"addf5e297e6cbf5341f9c07720693ca9ba0057b5","status":"affected","versionType":"git"},{"version":"b00628b1c7d595ae5b544e059c27b1f5828314b4","lessThan":"8327ed12e8ebc5436bfaa1786c49988894f9c8a6","status":"affected","versionType":"git"},{"version":"b00628b1c7d595ae5b544e059c27b1f5828314b4","lessThan":"7d80a9e745fa5b47da3bca001f186c02485c7c33","status":"affected","versionType":"git"},{"version":"b00628b1c7d595ae5b544e059c27b1f5828314b4","lessThan":"0281b919e175bb9c3128bd3872ac2903e9436e3f","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/bpf/helpers.c"],"versions":[{"version":"5.15","status":"affected"},{"version":"0","lessThan":"5.15","status":"unaffected","versionType":"semver"},{"version":"5.15.150","lessThanOrEqual":"5.15.*","status":"unaffected","versionType":"semver"},{"version":"6.1.80","lessThanOrEqual":"6.1.*","status":"unaffected","versionType":"semver"},{"version":"6.6.19","lessThanOrEqual":"6.6.*","status":"unaffected","versionType":"semver"},{"version":"6.7.7","lessThanOrEqual":"6.7.*","status":"unaffected","versionType":"semver"},{"version":"6.8","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":"5.15","versionEndExcluding":"5.15.150"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"5.15","versionEndExcluding":"6.1.80"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"5.15","versionEndExcluding":"6.6.19"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"5.15","versionEndExcluding":"6.7.7"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"5.15","versionEndExcluding":"6.8"}]}]}],"references":[{"url":"https://git.kernel.org/stable/c/5268bb02107b9eedfdcd51db75b407d10043368c"},{"url":"https://git.kernel.org/stable/c/addf5e297e6cbf5341f9c07720693ca9ba0057b5"},{"url":"https://git.kernel.org/stable/c/8327ed12e8ebc5436bfaa1786c49988894f9c8a6"},{"url":"https://git.kernel.org/stable/c/7d80a9e745fa5b47da3bca001f186c02485c7c33"},{"url":"https://git.kernel.org/stable/c/0281b919e175bb9c3128bd3872ac2903e9436e3f"}],"title":"bpf: Fix racing between bpf_timer_cancel_and_free and bpf_timer_cancel","x_generator":{"engine":"bippy-1.2.0"}},"adp":[{"problemTypes":[{"descriptions":[{"type":"CWE","lang":"en","description":"CWE-noinfo Not enough information"}]}],"metrics":[{"cvssV3_1":{"scope":"UNCHANGED","version":"3.1","baseScore":5.5,"attackVector":"LOCAL","baseSeverity":"MEDIUM","vectorString":"CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H","integrityImpact":"NONE","userInteraction":"NONE","attackComplexity":"LOW","availabilityImpact":"HIGH","privilegesRequired":"LOW","confidentialityImpact":"NONE"}},{"other":{"type":"ssvc","content":{"timestamp":"2024-04-03T19:13:11.173900Z","id":"CVE-2024-26737","options":[{"Exploitation":"none"},{"Automatable":"no"},{"Technical Impact":"partial"}],"role":"CISA Coordinator","version":"2.0.3"}}}],"title":"CISA ADP Vulnrichment","providerMetadata":{"orgId":"134c704f-9b21-4f2e-91b3-4a467353bcc0","shortName":"CISA-ADP","dateUpdated":"2024-11-04T18:51:47.375Z"}},{"providerMetadata":{"orgId":"af854a3a-2127-422b-91ae-364da2661108","shortName":"CVE","dateUpdated":"2024-08-02T00:14:13.230Z"},"title":"CVE Program Container","references":[{"url":"https://git.kernel.org/stable/c/5268bb02107b9eedfdcd51db75b407d10043368c","tags":["x_transferred"]},{"url":"https://git.kernel.org/stable/c/addf5e297e6cbf5341f9c07720693ca9ba0057b5","tags":["x_transferred"]},{"url":"https://git.kernel.org/stable/c/8327ed12e8ebc5436bfaa1786c49988894f9c8a6","tags":["x_transferred"]},{"url":"https://git.kernel.org/stable/c/7d80a9e745fa5b47da3bca001f186c02485c7c33","tags":["x_transferred"]},{"url":"https://git.kernel.org/stable/c/0281b919e175bb9c3128bd3872ac2903e9436e3f","tags":["x_transferred"]}]}]}}