Description

In the Linux kernel, the following vulnerability has been resolved:

xfrm: delete intermediate secpath entry in packet offload mode

Packets handled by hardware have added secpath as a way to inform XFRM
core code that this path was already handled. That secpath is not needed
at all after policy is checked and it is removed later in the stack.

However, in the case of IP forwarding is enabled (/proc/sys/net/ipv4/ip_forward),
that secpath is not removed and packets which already were handled are reentered
to the driver TX path with xfrm_offload set.

The following kernel panic is observed in mlx5 in such case:

mlx5_core 0000:04:00.0 enp4s0f0np0: Link up
mlx5_core 0000:04:00.1 enp4s0f1np1: Link up
Initializing XFRM netlink socket
IPsec XFRM device driver
BUG: kernel NULL pointer dereference, address: 0000000000000000
#PF: supervisor instruction fetch in kernel mode
#PF: error_code(0x0010) - not-present page
PGD 0 P4D 0
Oops: Oops: 0010 [#1] PREEMPT SMP
CPU: 0 UID: 0 PID: 0 Comm: swapper/0 Not tainted 6.13.0-rc1-alex #3
Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.13.0-1ubuntu1.1 04/01/2014
RIP: 0010:0x0
Code: Unable to access opcode bytes at 0xffffffffffffffd6.
RSP: 0018:ffffb87380003800 EFLAGS: 00010206
RAX: ffff8df004e02600 RBX: ffffb873800038d8 RCX: 00000000ffff98cf
RDX: ffff8df00733e108 RSI: ffff8df00521fb80 RDI: ffff8df001661f00
RBP: ffffb87380003850 R08: ffff8df013980000 R09: 0000000000000010
R10: 0000000000000002 R11: 0000000000000002 ...

Classification

CVE ID: CVE-2025-21720

Affected Products

Vendor: Linux, Linux

Product: Linux, Linux

Exploit Prediction Scoring System (EPSS)

EPSS Score: 0.03% (probability of being exploited)

EPSS Percentile: 4.16% (scored less or equal to compared to others)

EPSS Date: 2025-03-27 (when was this score calculated)

References

https://nvd.nist.gov/vuln/detail/CVE-2025-21720
https://git.kernel.org/stable/c/c6e1b2cac24b2a4d1dd472071021bf00c26450eb
https://git.kernel.org/stable/c/6945701ca1572f81bc9bb46f624b02eabb3eaf3e
https://git.kernel.org/stable/c/981ad4c882096e7375b8c2181dd4c3ee58ea5bae
https://git.kernel.org/stable/c/600258d555f0710b9c47fb78d2d80a4aecd608cc

Timeline