CVE-2025-21758 (GCVE-0-2025-21758)
Vulnerability from cvelistv5
Published
2025-02-27 02:18
Modified
2026-08-05 11:54
Severity ?
7.8 (High) - CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
Summary
In the Linux kernel, the following vulnerability has been resolved: ipv6: mcast: add RCU protection to mld_newpack() mld_newpack() can be called without RTNL or RCU being held. Note that we no longer can use sock_alloc_send_skb() because ipv6.igmp_sk uses GFP_KERNEL allocations which can sleep. Instead use alloc_skb() and charge the net->ipv6.igmp_sk socket under RCU protection.
References
Impacted products
Vendor Product Version
Linux Linux Version: b8ad0cbc58f703972e9e37c4e2a8081dd7e6a551
Version: b8ad0cbc58f703972e9e37c4e2a8081dd7e6a551
Version: b8ad0cbc58f703972e9e37c4e2a8081dd7e6a551
Version: b8ad0cbc58f703972e9e37c4e2a8081dd7e6a551
Version: b8ad0cbc58f703972e9e37c4e2a8081dd7e6a551
Version: b8ad0cbc58f703972e9e37c4e2a8081dd7e6a551
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              "value": "AV:L - The half of the race that mutates `dev-\u003end_net` (`dev_change_net_namespace()` / netns teardown) requires local action \u2014 network namespace creation and device moves \u2014 so the attack must be mounted locally. The MLD report path itself is also reachable by an adjacent attacker\u0027s MLD Query, but a remote peer alone cannot create the racing `dev_net()` mutation.\nAC:L - The attacker controls both sides of the race: they schedule the MLD report work at will (unprivileged multicast join, or by driving `igmp6_event_query`) and simultaneously perform the netns creation/destruction or device namespace move that flips `dev-\u003end_net`, looping until the window is hit. `cancel_delayed_work()` in `mld_ifc_stop_work`/`mld_gq_stop_work` is non-synchronous and `__mld_query_work` can re-arm `mc_gq_work` afterwards, so no barrier closes the window.\nPR:L - Joining an IPv6 multicast group via `setsockopt(IPV6_ADD_MEMBERSHIP)` needs no privilege at all, and the netns/netdev manipulation side is reachable by an ordinary user through unprivileged user namespaces (`unshare -Urn` grants CAP_NET_ADMIN inside the new netns). No real root in the init namespace is required.\nUI:N - The attacker drives both the multicast join and the namespace churn from their own processes; no victim action or cooperation is needed.\nS:U - The corruption is confined to kernel memory within the same security authority; no VM, IOMMU, or sandbox boundary is crossed.\nC:H - The stale `struct net *` yields a use-after-free read of freed slab memory and a dangling `struct sock *`, and `ip6_mc_hdr()` copies `inet6_sk(sk)-\u003ehop_limit` out of that freed object directly into a transmitted IPv6 header \u2014 leaking reclaimed kernel heap contents onto the network, with the UAF generally usable as a broader read primitive.\nI:H - `sock_alloc_send_skb()` performs refcount and ownership writes into the freed socket, and the skb\u0027s `sock_wfree` destructor later makes an indirect call through `sk-\u003esk_write_space` in memory an unprivileged attacker can reclaim by spraying raw IPv6 sockets \u2014 a control-flow hijack primitive, not merely a stray write.\nA:H - Dereferencing a freed `struct net`/`struct sock` reliably oopses or panics the kernel (KASAN-detectable UAF), and the race can be retried in a loop until it lands."
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    "datePublished": "2025-02-27T02:18:12.496Z",
    "dateReserved": "2024-12-29T08:45:45.761Z",
    "dateUpdated": "2026-08-05T11:54:10.964Z",
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