CVE-2026-64538

In the Linux kernel, the following vulnerability has been resolved: ipv6: Fix null-ptr-deref in…

Risk score: 41/100
CVSS: Not Scored
Exploit chance (30 days): 0.2%
Published: 27 Jul 2026

Open in the live forecast Today's forecast

What to know

What it is: In the Linux kernel, the following vulnerability has been resolved: ipv6: Fix null-ptr-deref in fib6_nh_mtu_change(). fib6_nh_mtu_change() re-fetches idev via __in6_dev_get(arg->dev) and dereferences idev->cnf.mtu6 without a NULL check. addrconf_ifdown() clears dev->ip6_ptr with RCU_INIT_POINTER() after rt6_disable_ip…
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-2026-64538: In the Linux kernel, the following vulnerability has been resolved: ipv6: Fix null-ptr-deref in… (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: Heap buffer overflow (CWE-122). 398 other warnings in 30 days
Same product: Earlier Canonical Ubuntu Linux warnings. 147 in the last 90 days

Why it is Yellow

Not yet scored by NVD
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: ipv6: Fix null-ptr-deref in fib6_nh_mtu_change(). fib6_nh_mtu_change() re-fetches idev via __in6_dev_get(arg->dev) and dereferences idev->cnf.mtu6 without a NULL check. addrconf_ifdown() clears dev->ip6_ptr with RCU_INIT_POINTER() after rt6_disable_ip() has released tb6_lock, so the RA-driven MTU walk can observe a NULL idev and oops. The caller rt6_mtu_change_route() guards its own __in6_dev_get(), but this re-fetch is unguarded; nexthop-backed routes survive addrconf_ifdown()'s flush, so the walk still reaches it after ip6_ptr is nulled. Return 0 when idev is NULL, matching rt6_mtu_change_route() and the fib6_mtu() fix in commit 5ad509c1fdad ("ipv6: Fix null-ptr-deref in fib6_mtu()."). Oops: general protection fault, ... KASAN: null-ptr-deref in range [0x00000000000002a8-0x00000000000002af] RIP: 0010:fib6_nh_mtu_change+0x203/0x990 rt6_mtu_change_route+0x141/0x1d0 __fib6_clean_all+0xd0/0x160 rt6_mtu_change+0xb4/0x100 ndisc_router_discovery+0x24b5/0x2cb0 icmpv6_rcv+0x12e9/0x1710 ipv6_rcv+0x39b/0x410

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