{"dataType":"CVE_RECORD","dataVersion":"5.2","cveMetadata":{"cveId":"CVE-2025-21823","assignerOrgId":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","state":"PUBLISHED","assignerShortName":"Linux","dateReserved":"2024-12-29T08:45:45.775Z","datePublished":"2025-02-27T20:06:14.074Z","dateUpdated":"2026-08-05T11:54:41.091Z"},"containers":{"cna":{"providerMetadata":{"orgId":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","shortName":"Linux","dateUpdated":"2026-08-05T11:54:41.091Z"},"descriptions":[{"lang":"en","value":"In the Linux kernel, the following vulnerability has been resolved:\n\nbatman-adv: Drop unmanaged ELP metric worker\n\nThe ELP worker needs to calculate new metric values for all neighbors\n\"reachable\" over an interface. Some of the used metric sources require\nlocks which might need to sleep. This sleep is incompatible with the RCU\nlist iterator used for the recorded neighbors. The initial approach to work\naround of this problem was to queue another work item per neighbor and then\nrun this in a new context.\n\nEven when this solved the RCU vs might_sleep() conflict, it has a major\nproblems: Nothing was stopping the work item in case it is not needed\nanymore - for example because one of the related interfaces was removed or\nthe batman-adv module was unloaded - resulting in potential invalid memory\naccesses.\n\nDirectly canceling the metric worker also has various problems:\n\n* cancel_work_sync for a to-be-deactivated interface is called with\n  rtnl_lock held. But the code in the ELP metric worker also tries to use\n  rtnl_lock() - which will never return in this case. This also means that\n  cancel_work_sync would never return because it is waiting for the worker\n  to finish.\n* iterating over the neighbor list for the to-be-deactivated interface is\n  currently done using the RCU specific methods. Which means that it is\n  possible to miss items when iterating over it without the associated\n  spinlock - a behaviour which is acceptable for a periodic metric check\n  but not for a cleanup routine (which must \"stop\" all still running\n  workers)\n\nThe better approch is to get rid of the per interface neighbor metric\nworker and handle everything in the interface worker. The original problems\nare solved by:\n\n* creating a list of neighbors which require new metric information inside\n  the RCU protected context, gathering the metric according to the new list\n  outside the RCU protected context\n* only use rcu_trylock inside metric gathering code to avoid a deadlock\n  when the cancel_delayed_work_sync is called in the interface removal code\n  (which is called with the rtnl_lock held)"}],"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 - The use-after-free is triggered by tearing down the batman-adv hard interface / soft interface (rtnetlink `ip link set ... nomaster`, `ip link del bat0`, or module unload) while unmanaged per-neighbour ELP metric workers are still queued, which requires local access; although adjacent mesh peers supply the neighbour entries that queue the workers, the deterministic self-contained attack is local via netlink.\nAC:L - The attacker controls both sides of the race — they create the neighbours (hundreds, via spoofed ELP frames) and issue the teardown — and because the worker blocks in `rtnl_lock()` while the teardown holds rtnl, it is guaranteed to resume with a stale `soft_iface`; the ordered single-threaded workqueue serializes the remaining workers past `free_netdev()`, making the window wide and repeatable.\nPR:L - An unprivileged local user can obtain CAP_NET_ADMIN/CAP_NET_RAW inside a user+network namespace (`unshare -Urn`), create a `batadv` link with `routing_algo BATMAN_V` (no `capable()` check in `batadv_softif_newlink`), enslave a veth, and drive the whole sequence; no real root is needed.\nUI:N - The attacker performs every step — mesh setup, neighbour generation and interface teardown — with no action required from any other user or administrator.\nS:U - The corruption is confined to kernel memory managed by the same security authority; there is no crossing of a VM, IOMMU or sandbox boundary.\nC:H - The worker reads through a freed `net_device`/`batadv_priv` allocation and prints `_netdev->name` to the kernel log, and `trace_batadv_dbg()` dereferences a `bat_priv->soft_iface` pointer read out of the freed slab — after heap-spray reclaim this yields an attacker-controlled read primitive and disclosure of freed kernel memory.\nI:H - A use-after-free on a reclaimable slab object gives the attacker control over the contents dereferenced by the worker (including a pointer that is followed), enabling heap-spray-based corruption and control-flow influence rather than merely stale reads.\nA:H - The unmanaged worker demonstrably panics the kernel — the sibling fix 522b1596ea19 carries a real crash trace through `batadv_v_elp_throughput_metric_update` — and any use-after-free of a freed net_device reliably oopses the machine."}]}],"affected":[{"product":"Linux","vendor":"Linux","defaultStatus":"unaffected","repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["net/batman-adv/bat_v.c","net/batman-adv/bat_v_elp.c","net/batman-adv/bat_v_elp.h","net/batman-adv/types.h"],"versions":[{"version":"c833484e5f3872a38fe232c663586069d5ad9645","lessThan":"1c334629176c2d644befc31a20d4bf75542f7631","status":"affected","versionType":"git"},{"version":"c833484e5f3872a38fe232c663586069d5ad9645","lessThan":"a0019971f340ae02ba54cf1861f72da7e03e6b66","status":"affected","versionType":"git"},{"version":"c833484e5f3872a38fe232c663586069d5ad9645","lessThan":"3c0e0aecb78cb2a2ca1dc701982d08fedb088dc6","status":"affected","versionType":"git"},{"version":"c833484e5f3872a38fe232c663586069d5ad9645","lessThan":"781a06fd265a8151f7601122d9c2e985663828ff","status":"affected","versionType":"git"},{"version":"c833484e5f3872a38fe232c663586069d5ad9645","lessThan":"a7aa2317285806640c844acd4cd2cd768e395264","status":"affected","versionType":"git"},{"version":"c833484e5f3872a38fe232c663586069d5ad9645","lessThan":"0fdc3c166ac17b26014313fa2b93696354511b24","status":"affected","versionType":"git"},{"version":"c833484e5f3872a38fe232c663586069d5ad9645","lessThan":"af264c2a9adc37f4bdf88ca7f3affa15d8c7de9e","status":"affected","versionType":"git"},{"version":"c833484e5f3872a38fe232c663586069d5ad9645","lessThan":"8c8ecc98f5c65947b0070a24bac11e12e47cc65d","status":"affected","versionType":"git"}]},{"product":"Linux","vendor":"Linux","defaultStatus":"affected","repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["net/batman-adv/bat_v.c","net/batman-adv/bat_v_elp.c","net/batman-adv/bat_v_elp.h","net/batman-adv/types.h"],"versions":[{"version":"4.6","status":"affected"},{"version":"0","lessThan":"4.6","status":"unaffected","versionType":"semver"},{"version":"5.4.291","lessThanOrEqual":"5.4.*","status":"unaffected","versionType":"semver"},{"version":"5.10.235","lessThanOrEqual":"5.10.*","status":"unaffected","versionType":"semver"},{"version":"5.15.179","lessThanOrEqual":"5.15.*","status":"unaffected","versionType":"semver"},{"version":"6.1.129","lessThanOrEqual":"6.1.*","status":"unaffected","versionType":"semver"},{"version":"6.6.79","lessThanOrEqual":"6.6.*","status":"unaffected","versionType":"semver"},{"version":"6.12.16","lessThanOrEqual":"6.12.*","status":"unaffected","versionType":"semver"},{"version":"6.13.4","lessThanOrEqual":"6.13.*","status":"unaffected","versionType":"semver"},{"version":"6.14","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":"4.6","versionEndExcluding":"5.4.291"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"4.6","versionEndExcluding":"5.10.235"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"4.6","versionEndExcluding":"5.15.179"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"4.6","versionEndExcluding":"6.1.129"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"4.6","versionEndExcluding":"6.6.79"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"4.6","versionEndExcluding":"6.12.16"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"4.6","versionEndExcluding":"6.13.4"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"4.6","versionEndExcluding":"6.14"}]}]}],"references":[{"url":"https://git.kernel.org/stable/c/1c334629176c2d644befc31a20d4bf75542f7631"},{"url":"https://git.kernel.org/stable/c/a0019971f340ae02ba54cf1861f72da7e03e6b66"},{"url":"https://git.kernel.org/stable/c/3c0e0aecb78cb2a2ca1dc701982d08fedb088dc6"},{"url":"https://git.kernel.org/stable/c/781a06fd265a8151f7601122d9c2e985663828ff"},{"url":"https://git.kernel.org/stable/c/a7aa2317285806640c844acd4cd2cd768e395264"},{"url":"https://git.kernel.org/stable/c/0fdc3c166ac17b26014313fa2b93696354511b24"},{"url":"https://git.kernel.org/stable/c/af264c2a9adc37f4bdf88ca7f3affa15d8c7de9e"},{"url":"https://git.kernel.org/stable/c/8c8ecc98f5c65947b0070a24bac11e12e47cc65d"}],"title":"batman-adv: Drop unmanaged ELP metric worker","x_generator":{"engine":"bippy-1.2.0"}},"adp":[{"title":"CVE Program Container","references":[{"url":"https://lists.debian.org/debian-lts-announce/2025/05/msg00030.html"},{"url":"https://lists.debian.org/debian-lts-announce/2025/03/msg00028.html"}],"providerMetadata":{"orgId":"af854a3a-2127-422b-91ae-364da2661108","shortName":"CVE","dateUpdated":"2025-11-03T20:59:56.036Z"}}]}}