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CVE-2026-64543

Canonical Ubuntu Linux: use-after-free

Risk score
62/100
CVSS
7.8 v3.1
Exploit chance (30 days)
0.1%
Published
27 Jul 2026

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What to know

What it is
In the Linux kernel, the following vulnerability has been resolved: tipc: fix use-after-free of the discoverer in tipc_disc_rcv() bearer_disable() frees b->disc with tipc_disc_delete()'s plain kfree(), but tipc_disc_rcv() still dereferences b->disc in RX softirq under rcu_read_lock() (tipc_udp_recv -> tipc_rcv -> tipc…
Affected
Canonical Ubuntu Linux
Fix
Apply the vendor's security update; see the linked advisory.
Exploitation
No known exploitation

Story map

Story map: Canonical Ubuntu LinuxTHE FLAWSTHE FIXCVE-2026-64543Use-after-freeCVSS 7.8 · EPSS 0%CVE-2026-93479Heap buffer overflow can leadto remote code executionCVSS 8.1 · EPSS 1%CVE-2026-15176Heap buffer overflow can leadto remote code executionCVSS 8.1 · EPSS 1%CVE-2026-97205NGINX Plus and NGINX OpenSource have a vulnerability inthe ngx_http_core_module…CVSS 8.1 · EPSS 1%FixCheck the linked advisory forthe concrete fix.Who is exposed{'products': ['NGINX Plus','NGINX Open Source'],'packages': [], 'versions': []}RED · ACT TODAYCanonical UbuntuLinuxA vulnerability exists in NGINXPlus and NGINX Open Sourcewhen a map directive uses regexmatching and the root directiveor access log format referencesthe map's regex capturevariables before referencing…Where it standsNo known exploitationHOW IT UNFOLDEDOfficial record on the left, the press on the right, oldest first.26 Oct · Ubuntu security noticesUSN-8955-1: nginx vulnerabilities5 Nov · Ubuntu security noticesUSN-8955-2: nginx vulnerabilities6 Nov · Ubuntu security noticesUSN-9003-1: Linux kernel (NVIDIA) vulnerabilitiesCONNECTS TOSame weaknessUse-after-free (CWE-416)399 other warnings in 30 days →Same productEarlier Canonical Ubuntu Linux warnings147 in the last 90 days →
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-2026-64543: Use-after-free (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

  1. 26 Oct, Ubuntu security notices (official): USN-8955-1: nginx vulnerabilities
  2. 5 Nov, Ubuntu security notices (official): USN-8955-2: nginx vulnerabilities
  3. 6 Nov, Ubuntu security notices (official): USN-9003-1: Linux kernel (NVIDIA) vulnerabilities

Connects to

Why it is Amber

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

Government and vendor bulletins

References

Original description

In the Linux kernel, the following vulnerability has been resolved: tipc: fix use-after-free of the discoverer in tipc_disc_rcv() bearer_disable() frees b->disc with tipc_disc_delete()'s plain kfree(), but tipc_disc_rcv() still dereferences b->disc in RX softirq under rcu_read_lock() (tipc_udp_recv -> tipc_rcv -> tipc_disc_rcv). L2 bearers are safe thanks to the synchronize_net() in tipc_disable_l2_media(), but the UDP bearer defers that call to the cleanup_bearer() workqueue, so the discoverer is freed with no grace period: BUG: KASAN: slab-use-after-free in tipc_disc_rcv (net/tipc/discover.c:149) Read of size 8 at addr ffff88802348b728 by task poc_tipc/184 <IRQ> tipc_disc_rcv (net/tipc/discover.c:149) tipc_rcv (net/tipc/node.c:2126) tipc_udp_recv (net/tipc/udp_media.c:391) udp_rcv (net/ipv4/udp.c:2643) ip_local_deliver_finish (net/ipv4/ip_input.c:241) </IRQ> Freed by task 181: kfree (mm/slub.c:6565) bearer_disable (net/tipc/bearer.c:418) tipc_nl_bearer_disable (net/tipc/bearer.c:1001) The bearer is freed with kfree_rcu(); free the discoverer the same way. Add an rcu_head to struct tipc_discoverer and free it and its skb from an RCU callback. Because the RCU callback (tipc_disc_free_rcu) lives in module text, a call_rcu() that is still pending when the tipc module is unloaded would invoke a freed function. Add an rcu_barrier() to tipc_exit() after the bearer subsystem has been torn down, so all pending discoverer callbacks have run before the module text goes away. Reachable from an unprivileged user namespace: the TIPCv2 genl family is netnsok and its bearer commands have no GENL_ADMIN_PERM. Needs CONFIG_TIPC and CONFIG_TIPC_MEDIA_UDP.

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