Vulnerability in Linux kernel (CVE-2025-21673)
Summary
Vulnerability in Linux kernel (CVE-2025-21673). Successful exploitation can lead to full system takeover.
Original description
The description as published by the source.
In the Linux kernel, the following vulnerability has been resolved:
smb: client: fix double free of TCP_Server_Info::hostname
When shutting down the server in cifs_put_tcp_session(), cifsd thread
might be reconnecting to multiple DFS targets before it realizes it
should exit the loop, so @server->hostname can't be freed as long as
cifsd thread isn't done. Otherwise the following can happen:
RIP: 0010:__slab_free+0x223/0x3c0
Code: 5e 41 5f c3 cc cc cc cc 4c 89 de 4c 89 cf 44 89 44 24 08 4c 89
1c 24 e8 fb cf 8e 00 44 8b 44 24 08 4c 8b 1c 24 e9 5f fe ff ff <0f>
0b 41 f7 45 08 00 0d 21 00 0f 85 2d ff ff ff e9 1f ff ff ff 80
RSP: 0018:ffffb26180dbfd08 EFLAGS: 00010246
RAX: ffff8ea34728e510 RBX: ffff8ea34728e500 RCX: 0000000000800068
RDX: 0000000000800068 RSI: 0000000000000000 RDI: ffff8ea340042400
RBP: ffffe112041ca380 R08: 0000000000000001 R09: 0000000000000000
R10: 6170732e31303000 R11: 70726f632e786563 R12: ffff8ea34728e500
R13: ffff8ea340042400 R14: ffff8ea34728e500 R15: 0000000000800068
FS: 0000000000000000(0000) GS:ffff8ea66fd80000(0000)
000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007ffc25376080 CR3: 000000012a2ba001 CR4:
PKRU: 55555554
Call Trace:
? show_trace_log_lvl+0x1c4/0x2df
? show_trace_log_lvl+0x1c4/0x2df
? __reconnect_target_unlocked+0x3e/0x160 [cifs]
? __die_body.cold+0x8/0xd
? die+0x2b/0x50
? do_trap+0xce/0x120
? __slab_free+0x223/0x3c0
? do_error_trap+0x65/0x80
? __slab_free+0x…
Source: NIST National Vulnerability Database NVD
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-2025-21673 has been found in Linux kernel.
Successful exploitation can lead to full system takeover. CVSS score: 9.8/10.
What to do: apply the vendor's official patched release.
If unsure, ask your IT team or search "Linux kernel CVE-2025-21673" on the vendor's site.
CVE-2025-21673 (Linux kernel) — CWE-415 / CVSS v3 9.8
Attack vector: remote (network-reachable) / unauthenticated / 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.
A vulnerability (CWE-415) exists in Linux kernel.
Check the vendor advisory for the affected versions of Linux kernel.
Severity: Critical (CVSS 9.8/10). Successful exploitation can lead to full system takeover.
Update to the patched release per vendor advisory.
Until the patch is applied: disable the affected feature, apply WAF rules, or restrict access via network ACLs.
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
-
1Identify 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。
-
2Post-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
Fix status by distribution
Fixed packages published by each distribution for this CVE
- BellSoft Alpaquita BELL-CVE-2025-21673 linux-lts
- Debian DEBIAN-CVE-2025-21673 linux
- Ubuntu UBUNTU-CVE-2025-21673 linux-hwe-edge
References
- advisory github.com
- advisory nvd.nist.gov
- package git.kernel.org
- web git.kernel.org
- web git.kernel.org
- web git.kernel.org