CVE-2026-64563

Canonical Ubuntu Linux: use-after-free can lead to denial of service

Risk score: 63/100
CVSS: 7.8 v3.1
Exploit chance (30 days): 0.2%
Published: 4 Aug 2026

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What to know

What it is: In the Linux kernel, the following vulnerability has been resolved: rhashtable: clear stale iter->p on table restart rhashtable_walk_start_check() has two restart paths when resuming a walk. When iter->walker.tbl is valid, it re-validates iter->p against the table and sets iter->p = NULL if the object is gone. When it…
Affected: Canonical Ubuntu Linux
Fix: Apply the vendor's security update; see the linked advisory.
Exploitation: No known exploitation

Story map

Story map: the flaws, the fix, how it unfolded and what it connects to. Boxes link to the record or article.

At a glance

Canonical Ubuntu Linux: Red, act today. A vulnerability exists in NGINX Plus and NGINX Open Source when a map directive uses regex matching and the root directive or access log format references the map's regex capture variables before referencing the map output variable. An unauthenticated attacker can exploit this vulnerability by sending crafted HTTP requests, causing a heap buffer overflow in the NGINX worker process leading to a restart, or potential…

The flaws

CVE-2026-64563: Use-after-free can lead to denial of service (CVSS 7.8 · EPSS 0%)
CVE-2026-93479: Heap buffer overflow can lead to remote code execution (CVSS 8.1 · EPSS 1%)
CVE-2026-15176: Heap buffer overflow can lead to remote code execution (CVSS 8.1 · EPSS 1%)
CVE-2026-97205: NGINX Plus and NGINX Open Source have a vulnerability in the ngx_http_core_module module (CVSS 8.1 · EPSS 1%)

The fix

Fix: Check the linked advisory for the concrete fix.

Who is exposed: {'products': ['NGINX Plus', 'NGINX Open Source'], 'packages': [], 'versions': []}

Where it stands

No known exploitation

How it unfolded

26 Oct, Ubuntu security notices (official): USN-8955-1: nginx vulnerabilities
5 Nov, Ubuntu security notices (official): USN-8955-2: nginx vulnerabilities
6 Nov, Ubuntu security notices (official): USN-9003-1: Linux kernel (NVIDIA) vulnerabilities

Connects to

Same weakness: Use-after-free (CWE-416). 399 other warnings in 30 days
Same product: Earlier Canonical Ubuntu Linux warnings. 147 in the last 90 days

Why it is Amber

CVSS 7.8 high
On your watchlist: linux kernel
Named in a government or vendor bulletin

Government and vendor bulletins

USN-9003-1: Linux kernel (NVIDIA) vulnerabilities

References

Original description

In the Linux kernel, the following vulnerability has been resolved: rhashtable: clear stale iter->p on table restart rhashtable_walk_start_check() has two restart paths when resuming a walk. When iter->walker.tbl is valid, it re-validates iter->p against the table and sets iter->p = NULL if the object is gone. When iter->walker.tbl is NULL (table was freed during resize), it resets slot and skip but forgets to clear iter->p. rhashtable_walk_next() then dereferences the stale iter->p, reading freed memory. This is a use-after-free. Any caller that does multi-fragment rhashtable walks across walk_stop/walk_start boundaries is affected. Concrete cases include netlink_diag (__netlink_diag_dump in net/netlink/diag.c) and TIPC (tipc_nl_sk_walk in net/tipc/socket.c). Crash stack (netlink_diag): BUG: KASAN: slab-use-after-free in rhashtable_walk_next+0x365/0x3c0 Read of size 8 at addr ffff88801a9d2438 (freed kmalloc-2k, offset 1080) Call Trace: rhashtable_walk_next+0x365/0x3c0 (lib/rhashtable.c:1016) __netlink_diag_dump+0x160/0x760 (net/netlink/diag.c:122) netlink_diag_dump+0xc2/0x240 netlink_dump+0x5bc/0x1270 netlink_recvmsg+0x7a3/0x980 sock_recvmsg+0x1bc/0x200 __sys_recvfrom+0x1d4/0x2c0

Last activity 6 Nov 2026. Patch Forecast updates every hour.