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Medium 5.5

Vulnerability in Linux kernel

CVE-2025-21653 First seen on SecPulse

Auto-generated summary

Assembled by SecPulse from the source data (CVSS, CWE, affected versions) using templates — no AI involved. Check the original description and references below for exact details.

A vulnerability tracked as CVE-2025-21653 has been found in Linux kernel.
Risk of unauthorized operations or information disclosure. CVSS score: 5.5/10.
What to do: apply the vendor's official patched release.
If unsure, ask your IT team or search "Linux kernel CVE-2025-21653" on the vendor's site.

CVE-2025-21653 (Linux kernel) — CVSS v3 5.5
Attack vector: local / no user interaction
Plan: 1) Audit SBOM/dependencies, 2) Stage→prod upgrade, 3) Add WAF/proxy monitoring on affected endpoints, 4) Hunt IOCs in logs.
Refs: see the GHSA / vendor advisory / patched release linked on this page.

What is the problem

A vulnerability (unclassified) exists in Linux kernel.

Affected scope

Check the vendor advisory for the affected versions of Linux kernel.

Severity

Severity: Medium (CVSS 5.5/10). Risk of unauthorized operations or information disclosure.

How to fix

Update to the patched release per vendor advisory.

Workaround

Until the patch is applied: disable the affected feature, apply WAF rules, or restrict access via network ACLs.

Detection

Search webserver/proxy logs for unusual request patterns matching this CVE's known IOCs. Audit SBOM/dependencies to find affected services.

Response actions

Concrete steps and command examples for SOC/SRE teams to execute in order

  1. 1
    Identify exposureidentify
    Audit SBOM/dependencies for affected components.

    資産台帳・SBOM・依存マニフェストで Linux kernel を使っているサービスとバージョンを洗い出す。

  2. 2
    Post-deployment verificationverify
    Confirm patched version is live in production

    パッチ適用後、ステージングで PoC または同等の悪用パターンを再現して脆弱性が閉じたことを確認。本番ではアクセスログ・WAF でアラート再発が無いか継続監視。

Affected packages

EcosystemPackageAffectedFixed
Linux Kernel
≥ 2.6.25, < 5.4.290
≥ 5.5.0, < 5.10.234
≥ 5.11.0, < 5.15.177
≥ 5.16.0, < 6.1.125
≥ 6.2.0, < 6.6.72
≥ 6.7.0, < 6.12.10
5.4.290
5.10.234
5.15.177
6.1.125
6.6.72
6.12.10

Fix status by distribution

Fixed packages published by each distribution for this CVE

Original description The description as published by the source.

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

net_sched: cls_flow: validate TCA_FLOW_RSHIFT attribute

syzbot found that TCA_FLOW_RSHIFT attribute was not validated.
Right shitfing a 32bit integer is undefined for large shift values.

UBSAN: shift-out-of-bounds in net/sched/cls_flow.c:329:23
shift exponent 9445 is too large for 32-bit type 'u32' (aka 'unsigned int')
CPU: 1 UID: 0 PID: 54 Comm: kworker/u8:3 Not tainted 6.13.0-rc3-syzkaller-00180-g4f619d518db9 #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 09/13/2024
Workqueue: ipv6_addrconf addrconf_dad_work
Call Trace:

__dump_stack lib/dump_stack.c:94 [inline]
dump_stack_lvl+0x241/0x360 lib/dump_stack.c:120
ubsan_epilogue lib/ubsan.c:231 [inline]
__ubsan_handle_shift_out_of_bounds+0x3c8/0x420 lib/ubsan.c:468
flow_classify+0x24d5/0x25b0 net/sched/cls_flow.c:329
tc_classify include/net/tc_wrapper.h:197 [inline]
__tcf_classify net/sched/cls_api.c:1771 [inline]
tcf_classify+0x420/0x1160 net/sched/cls_api.c:1867
sfb_classify net/sched/sch_sfb.c:260 [inline]
sfb_enqueue+0x3ad/0x18b0 net/sched/sch_sfb.c:318
dev_qdisc_enqueue+0x4b/0x290 net/core/dev.c:3793
__dev_xmit_skb net/core/dev.c:3889 [inline]
__dev_queue_xmit+0xf0e/0x3f50 net/core/dev.c:4400
dev_queue_xmit include/linux/netdevice.h:3168 [inline]
neigh_hh_output include/net/neighbour.h:523 [inline]
neigh_output include/net/neighbour.h:537 [inline]
ip_finish_output2+0xd41/0x1390 net/ipv…

Source: NIST National Vulnerability Database NVD GitHub Advisory

References

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