Summary
In the Linux kernel, the following vulnerability has been resolved: rpl: Fix use-after-free in...
In the Linux kernel, the following vulnerability has been resolved:
rpl: Fix use-after-free in rpl_do_srh_inline().
Running lwt_dst_cache_ref_loop.sh in selftest with KASAN triggers
the splat below [0].
rpl_do_srh_inline() fetches ipv6_hdr(skb) and accesses it after
skb_cow_head(), which is illegal as the header could be freed then.
Let's fix it by making oldhdr to a local struct instead of a pointer.
[0]:
[root@fedora net]# ./lwt_dst_cache_ref_loop.sh
...
TEST: rpl (input)
[ 57.631529] ==================================================================
BUG: KASAN: slab-use-after-free in rpl_do_srh_inline.isra.0 (net/ipv6/rpl_iptunnel.c:174)
Read of size 40 at addr ffff888122bf96d8 by task ping6/1543
CPU: 50 UID: 0 PID: 1543 Comm: ping6 Not tainted 6.16.0-rc5-01302-gfadd1e6231b1 #23 PREEMPT(voluntary)
Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.16.3-debian-1.16.3-2 04/01/2014
Call Trace:
dump_stack_lvl (lib/dump_stack.c:122)
print_report (mm/kasan/report.c:409 mm/kasan/report.c:521)
kasan_report (mm/kasan/report.c:221 mm/kasan/report.c:636)
kasan_check_range (mm/kasan/generic.c:175 (discriminator 1) mm/kasan/generic.c:189 (discriminator 1))
__asan_memmove (mm/kasan/shadow.c:94 (discriminator 2))
rpl_do_srh_inline.isra.0 (net/ipv6/rpl_iptunnel.c:174)
rpl_input (net/ipv6/rpl_iptunnel.c:201 net/ipv6/rpl_iptunnel.c:282)
lwtunnel_input (net/core/lwtunnel.c:459)
ipv6_rcv (./include/net/dst.h:471 (discriminator 1) ./include/net/dst.h:469 (discriminator 1) net/ipv6/ip6_input.c:79 (discriminator 1) ./include/linux/netfilter.h:317 (discriminator 1) ./include/linux/netfilter.h:311 (discriminator 1) net/ipv6/ip6_input.c:311 (discriminator 1))
__netif_receive_skb_one_core (net/core/dev.c:5967)
process_backlog (./include/linux/rcupdate.h:869 net/core/dev.c:6440)
__napi_poll.constprop.0 (net/core/dev.c:7452)
net_rx_action (net/core/dev.c:7518 net/core/dev.c:7643)
handle_softirqs (kernel/softirq.c:579)
do_softirq (kernel/softirq.c:480 (discriminator 20))
__local_bh_enable_ip (kernel/softirq.c:407)
__dev_queue_xmit (net/core/dev.c:4740)
ip6_finish_output2 (./include/linux/netdevice.h:3358 ./include/net/neighbour.h:526 ./include/net/neighbour.h:540 net/ipv6/ip6_output.c:141)
ip6_finish_output (net/ipv6/ip6_output.c:215 net/ipv6/ip6_output.c:226)
ip6_output (./include/linux/netfilter.h:306 net/ipv6/ip6_output.c:248)
ip6_send_skb (net/ipv6/ip6_output.c:1983)
rawv6_sendmsg (net/ipv6/raw.c:588 net/ipv6/raw.c:918)
__sys_sendto (net/socket.c:714 (discriminator 1) net/socket.c:729 (discriminator 1) net/socket.c:2228 (discriminator 1))
__x64_sys_sendto (net/socket.c:2231)
do_syscall_64 (arch/x86/entry/syscall_64.c:63 (discriminator 1) arch/x86/entry/syscall_64.c:94 (discriminator 1))
entry_SYSCALL_64_after_hwframe (arch/x86/entry/entry_64.S:130)
RIP: 0033:0x7f68cffb2a06
Code: 5d e8 41 8b 93 08 03 00 00 59 5e 48 83 f8 fc 75 19 83 e2 39 83 fa 08 75 11 e8 26 ff ff ff 66 0f 1f 44 00 00 48 8b 45 10 0f 05 <48> 8b 5d f8 c9 c3 0f 1f 40 00 f3 0f 1e fa 55 48 89 e5 48 83 ec 08
RSP: 002b:00007ffefb7c53d0 EFLAGS: 00000202 ORIG_RAX: 000000000000002c
RAX: ffffffffffffffda RBX: 0000564cd69f10a0 RCX: 00007f68cffb2a06
RDX: 0000000000000040 RSI: 0000564cd69f10a4 RDI: 0000000000000003
RBP: 00007ffefb7c53f0 R08: 0000564cd6a032ac R09: 000000000000001c
R10: 0000000000000000 R11: 0000000000000202 R12: 0000564cd69f10a4
R13: 0000000000000040 R14: 00007ffefb7c66e0 R15: 0000564cd69f10a0
Allocated by task 1543:
kasan_save_stack (mm/kasan/common.c:48)
kasan_save_track (mm/kasan/common.c:60 (discriminator 1) mm/kasan/common.c:69 (discriminator 1))
__kasan_slab_alloc (mm/kasan/common.c:319 mm/kasan/common.c:345)
kmem_cache_alloc_node_noprof (./include/linux/kasan.h:250 mm/slub.c:4148 mm/slub.c:4197 mm/slub.c:4249)
kmalloc_reserve (net/core/skbuff.c:581 (discriminator 88))
__alloc_skb (net/core/skbuff.c:669)
_ip6_append_data (net/ipv6/ip6_output.c:1672 (discriminator 1))
ip6
---truncated---
Impact
Memory is accessed after it has been freed, leading to undefined behavior in native code. Typical impact: memory corruption, crash, or potential code execution.
CVE-2025-38476 has a CVSS score of 7.8 (High). The vector is requires local access, low privileges required, and no user interaction. A CVSS score reflects the worst-case severity of the vulnerability, not your specific exposure. Whether this affects your application depends on whether the vulnerable code is present and reachable in your environment. No fixed version is listed yet, so configuration controls and monitoring matter more in the interim.
Affected versions
Security releases
Kodem intelligence
Severity tells you how bad this could be in the worst case. It does not tell you whether you are exposed. Exploitability and impact are functions of runtime truth: whether the vulnerable code is present, reachable, and actually executes in your application. A vulnerable package can sit in your dependency tree and never run.
Kodem, an Intelligent Application Security platform, uses runtime intelligence to reveal which vulnerabilities actually execute in production, so teams prioritize the ones that genuinely matter. Kodem's runtime-powered SCA identifies whether this CVE is reachable in your applications.
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Frequently Asked Questions
- What is CVE-2025-38476? CVE-2025-38476 is a high-severity use after free vulnerability. No fixed version is listed yet. Memory is accessed after it has been freed, leading to undefined behavior in native code.
- How severe is CVE-2025-38476? CVE-2025-38476 has a CVSS score of 7.8 (High). This score reflects the worst-case severity of the vulnerability, not your specific exposure. Whether it represents real risk in your environment depends on whether the vulnerable code is present and reachable.
- Is there a fix for CVE-2025-38476? No fixed version is listed for CVE-2025-38476 yet. Monitor the advisory for updates and apply mitigations in the interim.
- Is CVE-2025-38476 exploitable, and should I be worried? Whether CVE-2025-38476 is exploitable in your environment depends on whether the vulnerable code is present and reachable. A CVSS score is a worst-case rating; it does not account for your specific deployment, configuration, or usage patterns. Kodem, an Intelligent Application Security platform, uses runtime intelligence to show which vulnerabilities actually execute in production, so you can focus on the ones that represent real risk. Get a demo
- What actually determines whether CVE-2025-38476 is exploitable, and how bad it is? Exploitability and impact are not fixed properties of a CVE. They depend on runtime truth: whether the vulnerable code is present, reachable, and actually executes in your application. A high CVSS score on a dependency that never runs is not the same as real risk. Kodem, an Intelligent Application Security platform, uses runtime intelligence to reveal which vulnerabilities actually execute in production, so teams prioritize the ones that genuinely matter.