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CVE-2025-21865 medium CVSS 5.5

Out-of-Bounds Write in Linux kernel (CVE-2025-21865)

Summary

Out-of-bounds write in Linux kernel (CVE-2025-21865). Risk of unauthorized operations or information disclosure.

Original description

The description as published by the source.

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

gtp: Suppress list corruption splat in gtp_net_exit_batch_rtnl().

Brad Spengler reported the list_del() corruption splat in
gtp_net_exit_batch_rtnl(). [0]

Commit eb28fd76c0a0 ("gtp: Destroy device along with udp socket's netns
dismantle.") added the for_each_netdev() loop in gtp_net_exit_batch_rtnl()
to destroy devices in each netns as done in geneve and ip tunnels.

However, this could trigger ->dellink() twice for the same device during
->exit_batch_rtnl().

Say we have two netns A & B and gtp device B that resides in netns B but
whose UDP socket is in netns A.

  1. cleanup_net() processes netns A and then B.

  2. gtp_net_exit_batch_rtnl() finds the device B while iterating
    netns A's gn->gtp_dev_list and calls ->dellink().

[ device B is not yet unlinked from netns B
as unregister_netdevice_many() has not been called. ]

  1. gtp_net_exit_batch_rtnl() finds the device B while iterating
    netns B's for_each_netdev() and calls ->dellink().

gtp_dellink() cleans up the device's hash table, unlinks the dev from
gn->gtp_dev_list, and calls unregister_netdevice_queue().

Basically, calling gtp_dellink() multiple times is fine unless
CONFIG_DEBUG_LIST is enabled.

Let's remove for_each_netdev() in gtp_net_exit_batch_rtnl() and
delegate the destruction to default_device_exit_batch() as done
in bareudp.

[0]:
list_del corruption, ffff8880aaa62c00->next (autoslab_size_M_dev_P_net_core_dev_11127_8_1…

Source: NIST National Vulnerability Database NVD GitHub Advisory

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-2025-21865 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-2025-21865" on the vendor's site.

CVE-2025-21865 (Linux kernel) — CWE-787 / 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

Out-of-bounds write (CWE-787) 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 exposure identify 
    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 verification verify 
    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

Linux Kernel
[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"fixed":"5.4.291"}]},{"type":"ECOSYSTEM","events":[{"introduced":"5.5.0"},{"fixed":"5.10.235"}]},{"type":"ECOSYSTEM","events":[{"introduced":"5.11.0"},{"fixed":"5.15.179"}]},{"type":"ECOSYSTEM","events":[{"introduced":"5.16.0"},{"fixed":"6.1.130"}]},{"type":"ECOSYSTEM","events":[{"introduced":"6.2.0"},{"fixed":"6.6.80"}]},{"type":"ECOSYSTEM","events":[{"introduced":"6.7.0"},{"fixed":"6.12.17"}]},{"type":"ECOSYSTEM","events":[{"introduced":"6.13.0"},{"fixed":"6.13.5"}]}]

Fix status by distribution

Fixed packages published by each distribution for this CVE

References

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