CVE-2026-74561

Received Received - Intake

Use-After-Free in Linux Kernel Nexthop

Publication date: 2026-08-15

Last updated on: 2026-08-17

Assigner: kernel.org

Description

In the Linux kernel, the following vulnerability has been resolved: nexthop: avoid unlocked f6i_list walk in nh_rt_cache_flush nh_rt_cache_flush() walks nh->f6i_list during an RTNL-serialized nexthop replace without holding nh->lock, racing the unlocked IPv6 route add/delete that mutate the list under nh->lock and free fib6_info entries (nh_rt_cache_flush() is inlined into rtm_new_nexthop()): BUG: KASAN: slab-use-after-free in nh_rt_cache_flush (net/ipv4/nexthop.c:2243) Read of size 8 at addr ffff888012953e18 by task exploit/146 nh_rt_cache_flush (net/ipv4/nexthop.c:2243) replace_nexthop (net/ipv4/nexthop.c:2610) rtm_new_nexthop (net/ipv4/nexthop.c:3323) rtnetlink_rcv_msg (net/core/rtnetlink.c:7076) Unlike the other f6i_list walks, this one bumps each route's sernum via fib6_update_sernum_upto_root(), which needs tb6_lock; taking nh->lock around it would invert the established tb6_lock -> nh->lock order and deadlock. As the only purpose is to invalidate cached dsts, bump the IPv6 sernum for the whole netns with rt_genid_bump_ipv6() instead, mirroring the rt_cache_flush() already done for IPv4 just above.

CVSS Scores

EPSS Scores

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Meta Information

Published

2026-08-15

Last Modified

2026-08-17

Generated

2026-09-04

AI Q&A

2026-08-15

EPSS Evaluated

2026-09-03

NVD

CVE-2026-74561

EUVD

EUVD-2026-59626

Affected Vendors & Products

Vendor	Product	Version / Range
linux	linux_kernel	*

Helpful Resources

Exploitability

CWE

KEV

CWE ID	Description
CWE-UNKNOWN

Attack-Flow Graph

Executive Summary

This vulnerability in the Linux kernel involves a race condition in the nexthop handling code. The function nh_rt_cache_flush() accesses the nh->f6i_list without proper locking, which can lead to a use-after-free error when IPv6 routes are modified concurrently. The issue occurs because the function tries to update route serial numbers while holding a lock that could deadlock with other operations.

Detection Guidance

This vulnerability involves a race condition in the Linux kernel's nexthop handling for IPv6 routes. Detection requires checking kernel logs for slab-use-after-free errors related to nh_rt_cache_flush or nexthop operations. Monitor for crashes or memory corruption in networking components.

Impact Analysis

This vulnerability could cause system instability, crashes, or potential privilege escalation if exploited. It may lead to memory corruption, kernel panics, or unauthorized access to sensitive data due to the use-after-free condition in the kernel's networking subsystem.

Compliance Impact

This vulnerability is a kernel-level issue in Linux affecting IPv6 route handling. It does not directly relate to data privacy, access controls, or audit logging required by GDPR or HIPAA. Compliance impact would be indirect if this flaw enabled unauthorized network access or data exfiltration, but no evidence suggests such exposure exists.

Mitigation Strategies

Apply the latest Linux kernel patches addressing this issue. If immediate patching is not possible, restrict access to network configuration tools that could trigger nexthop operations until patched. Monitor system stability and kernel logs for signs of exploitation.

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