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CVE-2026-74630
ipv6: prevent in6_dev_get() from resurrecting inet6_dev
Published 2026-08-22 (2 months ago) by the Linux kernel CNA. Subsystem include/net. Debian urgency: not yet assigned.
What to do, per Debian release
Debian's own status for CVE-2026-74630 in every release this site tracks, and what each one means in practice. Every status below is the one the Debian Security Team publishes for this CVE. source
| Release | Status | Version | What this means |
|---|---|---|---|
| Debian 12bookworm | fixedDLA-4777-1 · 2026-09-08 · text | 6.1.187-1 | Update the kernel and reboot. DLA-4777-1 shipped the fix on 2026-09-08, in 6.1.187-1. A running kernel keeps the old code until the machine restarts. |
| Debian 13trixie | fixedDSA-6466-1 · 2026-08-25 · text | 6.12.105-1 | Update the kernel and reboot. DSA-6466-1 shipped the fix on 2026-08-25, in 6.12.105-1. A running kernel keeps the old code until the machine restarts. |
| Debian 14forky | fixed | 7.1.9-1 | Update the kernel and reboot. Fixed in 7.1.9-1. A running kernel keeps the old code until the machine restarts. |
| Debian unstablesid | fixed | 7.1.9-1 | Update the kernel and reboot. Fixed in 7.1.9-1. A running kernel keeps the old code until the machine restarts. |
| Debian 12bookworm · linux-6.12 | fixedDLA-4788-1 · 2026-09-19 · text | 6.12.107-1~deb12u1 | Update the kernel and reboot. DLA-4788-1 shipped the fix on 2026-09-19, in 6.12.107-1~deb12u1. A running kernel keeps the old code until the machine restarts. |
The vulnerability
What the bug is
in6_dev_get() reads dev->ip6_ptr under RCU and then unconditionally increments its refcount. Device teardown can clear the pointer and drop the last reference between these operations. The increment then resurrects an object whose RCU free has already been queued, so callers can use it after it is freed. Use refcount_inc_not_zero() and return NULL when the object has already reached zero. RCU keeps the memory accessible through the attempted reference acquisition, and a successful increment pins the object for the caller. An independent run on the exact unpatched 6f5156d7a31a (v7.2-rc3) kernel reproduced the invalid reference acquisition as UID 1000: refcount_t: addition on 0; use-after-free. ip6_mc_source+0xef4/0x17e0 It was followed by the corresponding reference underflow in ip6_mc_source(). The supplied trace from the same unpatched revision additionally shows the access after the RCU read-side section ends: BUG: KASAN: slab-use-after-free in mutex_lock+0x76/0xe0 Write of size 8 at addr ffff888015b50240 by task poc/1219 Bug found and triaged by OpenAI Security Research and validated by Trail of Bits.
Where it lives
The fix touches these files. If the subsystem is one you do not use, the practical exposure is lower, though the package is still the vulnerable one.
include/net/addrconf.h
- What this is
- NETWORKING [IPv4/IPv6]MAINTAINERS section matched on include/net/addrconf.h · netdev@vger.kernel.org · Maintained
Show whether Debian builds this, per release
Not established. This site could not find the build rule for the affected file in the kernel trees Debian ships, so it has no answer about whether Debian compiles this code. Read that as unknown, never as absent.
- bookworm, trixie, forky, sid, bookworm · linux-6.12?
- ?
- not established - no Makefile entry for the affected file
Where a release above reads "not established", no build rule for the affected file was found in that release's kernel tree. That is a gap in this lookup, not a finding that the code is absent.
From the configuration Debian publishes for every kernel flavour it builds. It covers only the architectures Debian ships a linux-config package for, and nothing about a kernel you built yourself. Debian's own status above stays authoritative about the source package.MAINTAINERS
Signals
- Published
- 2026-08-22 (2 months ago)source
- CVSS
- 7.8 high
CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:Hsource recompute it - Attack vector
- local (AV:L)source
- EPSS
- 0.13%, higher than 2.2% of all CVEssource
- CISA KEV
- not listedthe KEV catalogue
- Debian urgency
- not yet assignedsource
- Subsystem
- include/net
Upstream fixes
The versions the CNA records as introducing and fixing this, and the commit for each. source
| Introduced | Fixed in | Commit |
|---|---|---|
| 2.6.19 | 5.10.265 | 785d908f8d21 |
| 2.6.19 | 5.15.216 | aedcfefdb5b7 |
| 2.6.19 | 6.1.183 | 145812b678de |
| 2.6.19 | 6.6.152 | cc5bd568f9b7 |
| 2.6.19 | 6.12.104 | 1c206d461c68 |
| 2.6.19 | 6.18.45 | 680fbd794218 |
| 2.6.19 | 7.1.9 | 14e812ab41df |
| 2.6.19 | 7.2 | 0e243671bc7b |
Debian advisories
| Advisory | Date | Shipped to | Debian |
|---|---|---|---|
| DLA-4788-1 | 2026-09-19 | bookworm 6.12.107-1~deb12u1 | tracker |
| DLA-4777-1 | 2026-09-08 | bookworm 6.1.187-1 | tracker |
| DSA-6466-1 | 2026-08-25 | trixie 6.12.105-1 | tracker |
Why the CNA scored it this way
Quoted from the kernel CNA's own scoring file, word for word. A highlighted metric carries the most severe value CVSS v3.1 defines for it, which is what pushes the score up. source
- AV:LAttack vector, local
- The reliable path is local setsockopt(2) on IPv6 MCAST source-filter options (ipv6_setsockopt → do_ipv6_mcast_group_source → ip6_mc_source → in6_dev_get), reproduced as UID 1000; concurrent netdev unregister is also a local rtnetlink syscall, not remote packet delivery.
- AC:LAttack complexity, low
- An attacker in their own user+network namespace controls both sides of the race—hammering MCAST_JOIN/BLOCK/UNBLOCK_SOURCE setsockopt while deleting the bound veth via RTM_DELLINK—so the ip6_ptr clear and final in6_dev_put window is attacker-driven and retryable.
- PR:LPrivileges required, low
- Multicast setsockopt needs no capability, but hitting the unregister teardown that drops the last inet6_dev reference requires CAP_NET_ADMIN for RTM_DELLINK; that is ns_capable() in the netns user_ns and is obtainable by an unprivileged user via unshare -Urn, not init-namespace root.
- UI:NUser interaction, none
- Exploitation uses only the attacker's own IPv6 sockets, setsockopt calls, and netdev create/delete in their namespace; no victim mount, click, or other cooperation is required.
- S:UScope, unchanged
- The resurrected inet6_dev UAF corrupts kernel heap state within the host kernel authority (mutex_lock on freed mc_lock); it is standard local kernel memory corruption, not a VM escape, IOMMU bypass, or other cross-boundary impact.
- C:HConfidentiality impact, high
- Resurrecting a zero-refcount inet6_dev whose RCU free is already queued is a slab use-after-free; KASAN reported UAF on freed inet6_dev memory, and such heap UAFs enable disclosure via controlled reuse of the freed object.
- I:HIntegrity impact, high
- After resurrection the caller locks idev->mc_lock and mutates multicast state on freed memory (KASAN write in mutex_lock), giving attacker-influenced heap corruption that can be turned into arbitrary write or control-flow hijack.
- A:HAvailability impact, high
- The PoC triggers refcount_t addition-on-0 warnings, refcount underflow, and KASAN slab-use-after-free in mutex_lock, demonstrating immediate kernel memory corruption that can oops/panic and be repeated by re-running the race.