CyberSecBulletin
CVE-2026-63968NVD status: Analyzed

Linux: Loop with Unreachable Exit Condition

Published Updated By the CyberSecBulletin desk

CVE-2026-63968 is a high-severity loop with unreachable exit condition vulnerability in Linux, with a CVSS 3.1 base score of 7.5 out of 10. It can be exploited remotely over the network by an unauthenticated attacker, without any action from a user. The record lists versions 3948a7d92f7678e89e1776bb2d169afcad63b1ae, c87cd3cb309634bc8f50a54e2079424f219ac21f, 0f7b73c3452635de83b8711b31abdda8e49aad7b as the first without the flaw, so updating Linux to one of those releases or later removes the exposure. There is no confirmed exploitation so far. EPSS estimates a 0.66% chance of exploitation within 30 days, higher than 52% of scored CVEs.

Next patch cycle

High severity with no evidence of exploitation so far.

What to do

  1. Update Linux to 3948a7d92f7678e89e1776bb2d169afcad63b1ae or c87cd3cb309634bc8f50a54e2079424f219ac21f or 0f7b73c3452635de83b8711b31abdda8e49aad7b or ab9a10969a907b472a0196d999c08ff7144172e3, whichever matches your release line, or a later version.
  2. Update Linux Kernel to 6.1.176 or 6.6.143 or 6.12 or 6.12.93, whichever matches your release line, or a later version.
  3. Until you can update, restrict network access to the affected service so it is not reachable from untrusted networks.

Affected products and versions

VendorProductAffected versionsFixed in
LinuxLinuxd0ec61c9f3583b76aebdbb271f5c0d3fcccd48b2 up to, but not including, 3948a7d92f7678e89e1776bb2d169afcad63b1ae; 52da02521ede55fb86546c3fffd9377b3261b91f up to, but not including, c87cd3cb309634bc8f50a54e2079424f219ac21f; 34a949e7a0869dfa31a40416d2a56973fae1807b up to, but not including, 0f7b73c3452635de83b8711b31abdda8e49aad7b; d9ccb18f83ea2bb654289b6ecf014fd267cc988b up to, but not including, ab9a10969a907b472a0196d999c08ff7144172e3; d9ccb18f83ea2bb654289b6ecf014fd267cc988b up to, but not including, 9b9d5bd6e3d4c9cecab5407604b690684b2532d2; d9ccb18f83ea2bb654289b6ecf014fd267cc988b up to, but not including, 9c7da87c2dc860bb17ca1ece942495d28b1ce3b9; 11edcd026012ac18acee0f1514db3ed1b160fc6f; 6.1.128 up to, but not including, 6.1.176; and 4 more ranges3948a7d92f7678e89e1776bb2d169afcad63b1ae, c87cd3cb309634bc8f50a54e2079424f219ac21f, 0f7b73c3452635de83b8711b31abdda8e49aad7b, ab9a10969a907b472a0196d999c08ff7144172e3, 9b9d5bd6e3d4c9cecab5407604b690684b2532d2, 9c7da87c2dc860bb17ca1ece942495d28b1ce3b9
LinuxLinux Kernel6.1.128 up to, but not including, 6.1.176; 6.6.75 up to, but not including, 6.6.143; 6.11.11 up to, but not including, 6.12; 6.12.2 up to, but not including, 6.12.93; 6.13 up to, but not including, 6.18.35; 6.19 up to, but not including, 7.0.12; 7.16.1.176, 6.6.143, 6.12, 6.12.93, 6.18.35, 7.0.12

Version data comes from the organisation that assigned the CVE. Confirm against the vendor advisory before deciding you are unaffected.

How the severity score breaks down

Attack vector
NetworkCan be exploited remotely over a network, including the internet.
Attack complexity
LowNo special conditions are needed; the attack works reliably.
Privileges required
NoneNo account or login is needed.
User interaction
NoneNo action by a victim is required.
Scope
UnchangedImpact stays within the vulnerable component.
Confidentiality
NoneNo data is disclosed.
Integrity
NoneNothing can be modified.
Availability
HighThe component can be taken down completely.

Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H. Scored by CNA.

Official description

In the Linux kernel, the following vulnerability has been resolved: ipv6: fix possible infinite loop in fib6_select_path() Found while auditing the same pattern Sashiko reported in rt6_fill_node() [1]. Apply the same fix as commit f8d8ce1b515a ("ipv6: fix possible infinite loop in fib6_info_uses_dev()"). Writers holding tb6_lock can list_del_rcu(&first->fib6_siblings) without waiting for RCU readers; first->fib6_siblings.next then still points into the old ring and this softirq-side walker never reaches &first->fib6_siblings as its terminator. fib6_purge_rt() always WRITE_ONCE()s first->fib6_nsiblings to 0 before list_del_rcu(), so an inside-loop check is a reliable detach signal. [1] https://sashiko.dev/#/patchset/20260526020227.4857-1-jiayuan.chen%40linux.dev

Source: the CVE record as published by its numbering authority, via NVD and CVE.org.

The underlying weakness: Loop with Unreachable Exit Condition

The product contains an iteration or loop with an exit condition that cannot be reached, i.e., an infinite loop.

More Loop with Unreachable Exit Condition vulnerabilities (CWE-835)

Timeline

  1. CVE record published.
  2. CISA published its SSVC assessment (exploitation: none, automatable: yes, technical impact: partial).
  3. Record last changed materially (score, affected products, status or references).

References

Recent Loop with Unreachable Exit Condition vulnerabilities

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