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Linux KernelOperating system · Linux

CVE-2025-21675

MEDIUM · 5.5 CVSS v3.1 Published 2025-01-31
Fix available
A fix is available. Upgrade to 6.1.127 / 6.6.74 or later.
See remediation →
57/100
Remediation priority · Elevated
Zero-click Patch available

Official description Straight from the sourceThe vendor's or NVD's own wording, published unedited. Authoritative, but often terse — it says what broke, rarely what to do.

NVD · unedited
In the Linux kernel, the following vulnerability has been resolved: net/mlx5: Clear port select structure when fail to create Clear the port select structure on error so no stale values left after definers are destroyed. That's because the mlx5_lag_destroy_definers() always try to destroy all lag definers in the tt_map, so in the flow below lag definers get double-destroyed and cause kernel crash: mlx5_lag_port_sel_create() mlx5_lag_create_definers() mlx5_lag_create_definer() <- Failed on tt 1 mlx5_lag_destroy_definers() <- definers[tt=0] gets destroyed mlx5_lag_port_sel_create() mlx5_lag_create_definers() mlx5_lag_create_definer() <- Failed on tt 0 mlx5_lag_destroy_definers() <- definers[tt=0] gets double-destroyed Unable to handle kernel NULL pointer dereference at virtual address 0000000000000008 Mem abort info: ESR = 0x0000000096000005 EC = 0x25: DABT (current EL), IL = 32 bits SET = 0, FnV = 0 EA = 0, S1PTW = 0 FSC = 0x05: level 1 translation fault Data abort info: ISV = 0, ISS = 0x00000005, ISS2 = 0x00000000 CM = 0, WnR = 0, TnD = 0, TagAccess = 0 GCS = 0, Overlay = 0, DirtyBit = 0, Xs = 0 user pgtable: 64k pages, 48-bit VAs, pgdp=0000000112ce2e00 [0000000000000008] pgd=0000000000000000, p4d=0000000000000000, pud=0000000000000000 Internal error: Oops: 0000000096000005 [#1] PREEMPT SMP Modules linked in: iptable_raw bonding ip_gre ip6_gre gre ip6_tunnel tunnel6 geneve ip6_udp_tunnel udp_tunnel ipip tunnel4 ip_tunnel rdma_ucm(OE) rdma_cm(OE) iw_cm(OE) ib_ipoib(OE) ib_cm(OE) ib_umad(OE) mlx5_ib(OE) ib_uverbs(OE) mlx5_fwctl(OE) fwctl(OE) mlx5_core(OE) mlxdevm(OE) ib_core(OE) mlxfw(OE) memtrack(OE) mlx_compat(OE) openvswitch nsh nf_conncount psample xt_conntrack xt_MASQUERADE nf_conntrack_netlink nfnetlink xfrm_user xfrm_algo xt_addrtype iptable_filter iptable_nat nf_nat nf_conntrack nf_defrag_ipv6 nf_defrag_ipv4 br_netfilter bridge stp llc netconsole overlay efi_pstore sch_fq_codel zram ip_tables crct10dif_ce qemu_fw_cfg fuse ipv6 crc_ccitt [last unloaded: mlx_compat(OE)] CPU: 3 UID: 0 PID: 217 Comm: kworker/u53:2 Tainted: G OE 6.11.0+ #2 Tainted: [O]=OOT_MODULE, [E]=UNSIGNED_MODULE Hardware name: QEMU KVM Virtual Machine, BIOS 0.0.0 02/06/2015 Workqueue: mlx5_lag mlx5_do_bond_work [mlx5_core] pstate: 60400005 (nZCv daif +PAN -UAO -TCO -DIT -SSBS BTYPE=--) pc : mlx5_del_flow_rules+0x24/0x2c0 [mlx5_core] lr : mlx5_lag_destroy_definer+0x54/0x100 [mlx5_core] sp : ffff800085fafb00 x29: ffff800085fafb00 x28: ffff0000da0c8000 x27: 0000000000000000 x26: ffff0000da0c8000 x25: ffff0000da0c8000 x24: ffff0000da0c8000 x23: ffff0000c31f81a0 x22: 0400000000000000 x21: ffff0000da0c8000 x20: 0000000000000000 x19: 0000000000000001 x18: 0000000000000000 x17: 0000000000000000 x16: 0000000000000000 x15: 0000ffff8b0c9350 x14: 0000000000000000 x13: ffff800081390d18 x12: ffff800081dc3cc0 x11: 0000000000000001 x10: 0000000000000b10 x9 : ffff80007ab7304c x8 : ffff0000d00711f0 x7 : 0000000000000004 x6 : 0000000000000190 x5 : ffff00027edb3010 x4 : 0000000000000000 x3 : 0000000000000000 x2 : ffff0000d39b8000 x1 : ffff0000d39b8000 x0 : 0400000000000000 Call trace: mlx5_del_flow_rules+0x24/0x2c0 [mlx5_core] mlx5_lag_destroy_definer+0x54/0x100 [mlx5_core] mlx5_lag_destroy_definers+0xa0/0x108 [mlx5_core] mlx5_lag_port_sel_create+0x2d4/0x6f8 [mlx5_core] mlx5_activate_lag+0x60c/0x6f8 [mlx5_core] mlx5_do_bond_work+0x284/0x5c8 [mlx5_core] process_one_work+0x170/0x3e0 worker_thread+0x2d8/0x3e0 kthread+0x11c/0x128 ret_from_fork+0x10/0x20 Code: a9025bf5 aa0003f6 a90363f7 f90023f9 (f9400400) ---[ end trace 0000000000000000 ]---

Technical summary Written by usOur analysis, written from the advisory, the CVSS vector and the affected-version data. It adds context the advisory leaves out, and never invents facts that are not in the source.

dbcve analysis
How this class of weakness works · CWE-476

The code follows a pointer that is null, crashing the process. An attacker who can reliably trigger it turns the crash into a denial of service. The fix is checking for null before use and handling the failure path gracefully.

General guidance for the null pointer dereference class — the official description and references above are authoritative for this specific CVE. Want a bespoke review and a reviewed fix? Ask our team →

Affected products & versions What the vendor confirmedThe version ranges the vendor confirmed as vulnerable. If your version sits inside a range here, treat yourself as exposed until you have upgraded.

NVD · CPE data
Linux KernelOperating system
Affected:>= 5.16, < 6.1.127>= 6.2, < 6.6.74>= 6.7, < 6.12.11= 6.13

CVSS breakdown How the score is builtThe industry scoring standard. It rates how the flaw is reached, what it takes to exploit, and what an attacker gains — the score is derived from those, not the other way round.

From the vector
Attack vector
Local
Complexity
Low
Privileges
Low
User interaction
None
Scope
Unchanged
Confidentiality
None
Integrity
None
Availability
High

CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H

Remediation Closing itWhat it takes to close this. Where a vendor fix exists we point at it; where none exists we say so plainly, and can build one. Effort estimates are scoped from the advisory, not from your codebase.

dbcve · scoped
Upgrade available Upgrade to 6.1.127 / 6.6.74 / 6.12.11 or later
Fixed in 6.1.1276.6.746.12.11
Vendor patch git.kernel.org →
Recommended fix High confidence

Upgrade to kernel 6.1.127 (for 5.16-6.1.x), 6.6.74 (for 6.2-6.6.x), 6.12.11 (for 6.7-6.12.x), or 6.13.1+ (for 6.13.x)

  1. Identify the currently running kernel version using 'uname -r'
  2. Check which affected version range your kernel falls into: >= 5.16 && < 6.1.127, >= 6.2 && < 6.6.74, >= 6.7 && < 6.12.11, or = 6.13
  3. Upgrade the Linux kernel to the first fixed version in your branch: 6.1.127 for 5.16-6.1.x, 6.6.74 for 6.2-6.6.x, 6.12.11 for 6.7-6.12.x, or 6.13.1 or later for 6.13.x
  4. Reboot the system to load the fixed kernel
  5. Verify the fix is applied by checking the kernel version and confirming mlx5_core module loads without errors
Caveat Kernel upgrades carry standard reboot requirements and may include other changes; test in staging if possible

Generated from the published advisory — verify against the referenced sources before acting.

We can perform the upgrade in your staging environment and verify nothing breaks — typical engagement from $2,850. Get the upgrade done

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References Go to the primary sourcePrimary sources — vendor advisories, patches and trackers. Where our summary and a reference disagree, the reference wins.

Primary sources

Practitioner notes

Contributed

Peer-ranked notes from engineers who’ve handled CVE-2025-21675 in production — separate from our analysis above.

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