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CVE-2025-21857— net/sched: cls_api: fix error handling causing NULL dereference

Quick assessment

Affected
Linux Linux
Exploitation
No confirmed in-the-wild exploitation; assess based on exposure
Recommended action
Check the vendor advisory and references for a fixed version. If immediate upgrade is impossible, restrict exposure and increase monitoring.

Linux kernel是美国Linux基金会的开源操作系统Linux所使用的内核。 Linux kernel存在安全漏洞，该漏洞源于错误处理不当，可能导致空指针取消引用。

AI Predicted 6.5 Difficulty: Moderate EPSS 0.22% · P12

Possible ATT&CK Techniques 1 AI

T1059 · Command and Scripting Interpreter

Affected Version Matrix 10

VendorProduct Version RangeStatus
Linux Linux 80cd22c35c9001fe72bf614d29439de41933deca< de4b679aa3b4da7ec34f639df068b914f20e3c3c affected
80cd22c35c9001fe72bf614d29439de41933deca< 3e4c56cf41876ef2a82f0877fe2a67648f8632b8 affected
80cd22c35c9001fe72bf614d29439de41933deca< 3c74b5787caf59bb1e9c5fe0a360643a71eb1e8a affected
80cd22c35c9001fe72bf614d29439de41933deca< 071ed42cff4fcdd89025d966d48eabef59913bf2 affected
6.3 affected
< 6.3 unaffected
6.6.80≤ 6.6.* unaffected
6.12.17≤ 6.12.* unaffected
… +2 more rows
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I. Basic Information for CVE-2025-21857

Vulnerability Information
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Vulnerability Title
net/sched: cls_api: fix error handling causing NULL dereference
Source: CVE Program / CVE List V5
Vulnerability Description
In the Linux kernel, the following vulnerability has been resolved: net/sched: cls_api: fix error handling causing NULL dereference tcf_exts_miss_cookie_base_alloc() calls xa_alloc_cyclic() which can return 1 if the allocation succeeded after wrapping. This was treated as an error, with value 1 returned to caller tcf_exts_init_ex() which sets exts->actions to NULL and returns 1 to caller fl_change(). fl_change() treats err == 1 as success, calling tcf_exts_validate_ex() which calls tcf_action_init() with exts->actions as argument, where it is dereferenced. Example trace: BUG: kernel NULL pointer dereference, address: 0000000000000000 CPU: 114 PID: 16151 Comm: handler114 Kdump: loaded Not tainted 5.14.0-503.16.1.el9_5.x86_64 #1 RIP: 0010:tcf_action_init+0x1f8/0x2c0 Call Trace: tcf_action_init+0x1f8/0x2c0 tcf_exts_validate_ex+0x175/0x190 fl_change+0x537/0x1120 [cls_flower]
Source: CVE Program / CVE List V5
CVSS Information
N/A
Source: CVE Program / CVE List V5
Vulnerability Type
N/A
Source: CVE Program / CVE List V5
Vulnerability Title
Linux kernel 安全漏洞
Source: CNNVD (China National Vulnerability Database)
Vulnerability Description
Linux kernel是美国Linux基金会的开源操作系统Linux所使用的内核。 Linux kernel存在安全漏洞，该漏洞源于错误处理不当，可能导致空指针取消引用。
Source: CNNVD (China National Vulnerability Database)
CVSS Information
N/A
Source: CNNVD (China National Vulnerability Database)
Vulnerability Type
N/A
Source: CNNVD (China National Vulnerability Database)

Affected Products

Vendor Product Affected Versions CPE Subscribe
Linux Linux 80cd22c35c9001fe72bf614d29439de41933deca ~ de4b679aa3b4da7ec34f639df068b914f20e3c3c -
Linux Linux 6.3 -

II. Public POCs for CVE-2025-21857

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III. Intelligence Information for CVE-2025-21857

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Other References for CVE-2025-21857 (4)

Same Patch Batch · Linux · 2025-03-12 · 26 CVEs total

CVE-2024-58087 9.8 CRITICAL ksmbd: fix racy issue from session lookup and expire
CVE-2025-21850 9.8 CRITICAL nvmet: Fix crash when a namespace is disabled
CVE-2025-21855 8.6 HIGH ibmvnic: Don't reference skb after sending to VIOS
CVE-2025-21864 7.8 HIGH tcp: drop secpath at the same time as we currently drop dst
CVE-2024-58089 7.8 HIGH btrfs: fix double accounting race when btrfs_run_delalloc_range() failed
CVE-2025-21858 7.8 HIGH geneve: Fix use-after-free in geneve_find_dev().
CVE-2025-21851 7.8 HIGH bpf: Fix softlockup in arena_map_free on 64k page kernel
CVE-2025-21844 7.5 HIGH smb: client: Add check for next_buffer in receive_encrypted_standard()
CVE-2025-21853 bpf: avoid holding freeze_mutex during mmap operation
CVE-2024-58088 bpf: Fix deadlock when freeing cgroup storage
CVE-2025-21845 mtd: spi-nor: sst: Fix SST write failure
CVE-2025-21846 acct: perform last write from workqueue
CVE-2025-21848 nfp: bpf: Add check for nfp_app_ctrl_msg_alloc()
CVE-2025-21847 ASoC: SOF: stream-ipc: Check for cstream nullity in sof_ipc_msg_data()
CVE-2025-21849 drm/i915/gt: Use spin_lock_irqsave() in interruptible context
CVE-2025-21852 net: Add rx_skb of kfree_skb to raw_tp_null_args[].
CVE-2025-21866 powerpc/code-patching: Fix KASAN hit by not flagging text patching area as VM_ALLOC
CVE-2025-21854 sockmap, vsock: For connectible sockets allow only connected
CVE-2025-21856 s390/ism: add release function for struct device
CVE-2025-21859 USB: gadget: f_midi: f_midi_complete to call queue_work

Showing top 20 of 26 CVEs. View all on vendor page &rarr; →

IV. Related Vulnerabilities

Same product: Linux
Same vendor: Linux

V. Comments for CVE-2025-21857

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