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CVE-2026-52981
neigh: let neigh_xmit take skb ownership
Published 2026-06-24 (4 months ago) by the Linux kernel CNA. Subsystem net/core. Debian urgency: not yet assigned.
What to do, per Debian release
Debian's own status for CVE-2026-52981 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-4665-1 · 2026-07-03 · text | 6.1.176-1 | Update the kernel and reboot. DLA-4665-1 shipped the fix on 2026-07-03, in 6.1.176-1. A running kernel keeps the old code until the machine restarts. |
| Debian 13trixie | fixed | 6.12.94-1 | Update the kernel and reboot. Fixed in 6.12.94-1. A running kernel keeps the old code until the machine restarts. |
| Debian 14forky | fixed | 7.0.10-1 | Update the kernel and reboot. Fixed in 7.0.10-1. A running kernel keeps the old code until the machine restarts. |
| Debian unstablesid | fixed | 7.0.10-1 | Update the kernel and reboot. Fixed in 7.0.10-1. A running kernel keeps the old code until the machine restarts. |
The vulnerability
What the bug is
neigh_xmit always releases the skb, except when no neighbour table is found. But even the first added user of neigh_xmit (mpls) relied on neigh_xmit to release the skb (or queue it for tx). sashiko reported: If neigh_xmit() is called with an uninitialized neighbor table (for example, NEIGH_ND_TABLE when IPv6 is disabled), it returns -EAFNOSUPPORT and bypasses its internal out_kfree_skb error path. Because the return value of neigh_xmit() is ignored here, does this leak the SKB? Assume full ownership and remove the last code path that doesn't xmit or free skb.
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.
net/core/neighbour.c
- What this is
- NETWORKING [GENERAL]MAINTAINERS section matched on net/ · netdev@vger.kernel.org · Maintained
Show whether Debian builds this, per release
Debian builds this code. Every release below compiles the affected file into the kernels it ships.
- bookworm, trixie, forky, sidy
- y
- built into the kernel image on every flavour - only a patch removes it
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 Debian linux-config packages
Signals
- Published
- 2026-06-24 (4 months ago)source
- CVSS
- 7.5 high
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:Hsource recompute it - Attack vector
- network (AV:N)source
- EPSS
- 0.53%, higher than 43.7% of all CVEssource
- CISA KEV
- not listedthe KEV catalogue
- Debian urgency
- not yet assignedsource
- Subsystem
- net/core
Upstream fixes
The versions the CNA records as introducing and fixing this, and the commit for each. source
| Introduced | Fixed in | Commit |
|---|---|---|
| 4.1 | 6.1.175 | 8a89054a1ec0 |
| 4.1 | 6.6.141 | 9247d59ca15b |
| 4.1 | 6.12.91 | 0084712e0bee |
| 4.1 | 6.18.33 | 63063ba60d2d |
| 4.1 | 7.0.10 | 445e45a2c3a0 |
| 4.1 | 7.1 | 4438113be604 |
Debian advisories
| Advisory | Date | Shipped to | Debian |
|---|---|---|---|
| DLA-4671-1 | 2026-07-05 | bullseye 6.1.176-1~deb11u1 | tracker |
| DLA-4665-1 | 2026-07-03 | bookworm 6.1.176-1 | 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:NAttack vector, network
- An unauthenticated packet sender can trigger the vulnerable `neigh_xmit()` path through configured network forwarding paths such as nftables netdev forwarding or MPLS forwarding. In the highest reasonable deployment, this is an exposed router/firewall datapath reachable by network traffic.
- AC:LAttack complexity, low
- The bug is deterministic once the forwarding path uses a real neighbor table whose pointer is NULL, such as `NEIGH_ND_TABLE` when IPv6 neighbor discovery is unavailable. No race or heap shaping is required; repeated matching packets repeatedly leak skbs.
- PR:NPrivileges required, none
- The attacker does not need privileges to send packets into an already configured vulnerable forwarding datapath. Although installing such rules/routes requires administrative network privileges, the packet-triggering attack itself is unauthenticated.
- UI:NUser interaction, none
- No victim user action is required after the affected forwarding configuration exists. The attacker only sends traffic that reaches the vulnerable path.
- S:UScope, unchanged
- The impact remains within the kernel/networking security authority of the affected system. There is no VM escape, sandbox boundary crossing, or separate security scope involved.
- C:NConfidentiality impact, none
- The flaw is an skb memory leak caused by failing to free the packet buffer on the missing-table error path. It does not expose leaked memory contents to the attacker.
- I:NIntegrity impact, none
- The bug does not provide a memory corruption or data modification primitive. It only loses ownership of allocated skbs.
- A:HAvailability impact, high
- An attacker can repeatedly trigger the leak with packets, consuming kernel memory and plausibly causing OOM, hangs, packet processing failure, or system-wide denial of service. Kernel memory exhaustion is a high availability impact.