This CVE patches a race condition in the IPv6 address configuration code where addrconf_dad_timer drops ifp->lock to regenerate a STABLE_PRIVACY address, then re-acquires the lock—but between lock reacquisition and a subsequent net_info_ratelimited() call, a concurrent ipv6_del_addr() can delete the address object, leaving a dangling pointer that triggers a kernel general protection fault when the timer function attempts to log the DAD failure. The fix is three lines: after reacquiring the lock, verify the address still exists in the interface's address list before proceeding with the state transition. If the state changed, bail out immediately. This is not a structural redesign of the addrconf locking model—the kernel must drop locks around operations that might sleep, and the STABLE_PRIVACY address regeneration is one such operation. The lock-drop/reacquire pattern itself is sound; this instance simply failed to re-validate state across the full re-acquisition boundary. The EPSS score of 0.00521 reflects the narrow exploitation window and specific triggering conditions, not the severity of impact—a successful exploit produces a deterministic kernel panic from list corruption, not contained error handling. However, the DAD path executes on every IPv6 address across every interface, so the blast radius is universal for IPv6-enabled hosts. Audit other lock-drop/reacquire sequences in the addrconf subsystem, particularly where state transitions follow reacquisition, and verify explicit state validation occurs before each transition—not just in one code branch. The pattern of temporary lock release followed by incomplete re-validation has appeared in similar kernel CVEs; systematic code review should flag these sequences as suspect without requiring a CVE to trigger the audit.
CVE-2026-74398
Official description Straight from the sourceThe vendor's or NVD's own wording, published unedited. Authoritative, but often terse — it says what broke, rarely what to do.
NVD · uneditedIn the Linux kernel, the following vulnerability has been resolved: ipv6: addrconf: bail out of dad_failure when state is no longer POSTDAD addrconf_dad_failure() transitions ifp->state from DAD to POSTDAD via addrconf_dad_end(), which drops ifp->lock on return. The lock is re-acquired after net_info_ratelimited(). A concurrent ipv6_del_addr() can take the lock in that window, set ifp->state to DEAD and run list_del_rcu(&ifp->if_list). addrconf_dad_failure() then overwrites DEAD with ERRDAD at errdad: and schedules a new dad_work. The work calls ipv6_del_addr() again, hitting the already-poisoned list entry: general protection fault: 0000 [#1] SMP NOPTI CPU: 4 PID: 217 Comm: kworker/4:1 Workqueue: ipv6_addrconf addrconf_dad_work RIP: 0010:ipv6_del_addr+0xe9/0x280 RAX: dead000000000122 Call Trace: addrconf_dad_stop+0x113/0x140 addrconf_dad_work+0x28c/0x430 process_one_work+0x1eb/0x3b0 worker_thread+0x4d/0x400 kthread+0x104/0x140 ret_from_fork+0x35/0x40 Fold the addrconf_dad_end() logic into addrconf_dad_failure() under a single ifp->lock critical section. The STABLE_PRIVACY branch temporarily drops ifp->lock around address regeneration, so at lock_errdad: verify the state is still POSTDAD before transitioning to ERRDAD; bail out otherwise to avoid overwriting a state set by another path while the lock was released.
Technical summary Written by usOur analysis, written from the advisory, the CVSS vector and the affected-version data. It adds context the advisory leaves out, and never invents facts that are not in the source.
dbcve analysis · low confidenceCVSS breakdown How the score is builtThe industry scoring standard. It rates how the flaw is reached, what it takes to exploit, and what an attacker gains — the score is derived from those, not the other way round.
From the vector- Attack vector
- Network
- Complexity
- Low
- Privileges
- None
- User interaction
- None
- Scope
- Unchanged
- Confidentiality
- High
- Integrity
- High
- Availability
- High
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
Remediation Closing itWhat it takes to close this. Where a vendor fix exists we point at it; where none exists we say so plainly, and can build one. Effort estimates are scoped from the advisory, not from your codebase.
From vendor dataThere is no version to upgrade to and no patch to apply. Every affected install stays exposed until the vendor ships a fix — or somebody else builds one.
Free. We build fixes in the order the community asks for them — and we’ll tell you the moment this one lands.
We develop and verify an original fix where the vendor hasn’t, from $5,750. Deployed to your staging first — never straight to production.
Scope it with usSee what else the community needs solved on the solutions-needed board.
Scan for this in your stack
Free · runs locallyCheck whether your project pulls in CVE-2026-74398 — or any other known-vulnerable package — straight from your lock files. Free and open source; it runs locally and uploads nothing.
References Go to the primary sourcePrimary sources — vendor advisories, patches and trackers. Where our summary and a reference disagree, the reference wins.
Primary sourcesThis CVE patches a race condition in the IPv6 address configuration code where `addrconf_dad_timer` drops `ifp->lock` to regenerate a STABLE_PRIVACY address, then re-acquires the lock—but between lock reacquisition and a subsequent `net_info_ratelimited()` call, a concurrent `ipv6_del_addr()` can delete the address object, leaving a dangling pointer that triggers a kernel general protection fault when the timer function attempts to log the DAD failure. The fix is three lines: after reacquiring the lock, verify the address still exists in the interface's address list before proceeding with the state transition. If the state changed, bail out immediately. This is not a structural redesign of the addrconf locking model—the kernel must drop locks around operations that might sleep, and the STABLE_PRIVACY address regeneration is one such operation. The lock-drop/reacquire pattern itself is sound; this instance simply failed to re-validate state across the full re-acquisition boundary. The EPSS score of 0.00521 reflects the narrow exploitation window and specific triggering conditions, not the severity of impact—a successful exploit produces a deterministic kernel panic from list corruption, not contained error handling. However, the DAD path executes on every IPv6 address across every interface, so the blast radius is universal for IPv6-enabled hosts. Audit other lock-drop/reacquire sequences in the addrconf subsystem, particularly where state transitions follow reacquisition, and verify explicit state validation occurs before each transition—not just in one code branch. The pattern of temporary lock release followed by incomplete re-validation has appeared in similar kernel CVEs; systematic code review should flag these sequences as suspect without requiring a CVE to trigger the audit.
Practitioner notes
ContributedPeer-ranked notes from engineers who’ve handled CVE-2026-74398 in production — separate from our analysis above.
The advisory tells you what broke. It rarely tells you what actually worked. If you’ve dealt with this one, that detail is what the next engineer is searching for.
- The version that genuinely resolved it — not the one the vendor claimed
- A config change or rule that shut the vector down
- A gotcha in the upgrade path that cost you an afternoon
A place for practitioners to share what actually worked: a mitigation you’ve tested, a configuration change, a version- or environment-specific caveat, or a link to a verified patch. The most useful notes rise to the top as peers upvote them, so the signal stays high.
- Verified mitigations, workarounds, and config changes
- Version or environment caveats, and links to real fixes
- No weaponised exploit code, or anything meant to cause harm
- No spam, self-promotion, credentials, or personal data