Critical · CVSS 9.8CVE-2025-21673

smb: client: fix double free of TCP_Server_Info::hostnameCVE-2025-21673

Answer in brief

CVE-2025-21673 records a Critical severity (CVSS 9.8) vulnerability in smb: client: fix double free of TCP_Server_Info::hostname. The current sources do not mark it as known exploited. The current feed maps Linux/Linux (generic), Linux/Linux (generic), Linux/Linux (generic). Check affected ranges and fixed versions before updating.

Analysis pending evidence review

HOL Guard separates source facts from reviewed analysis. See the methodology.

Published Jan 31, 2025Updated Oct 30, 2026Source checked Nov 5, 2026First seen by HOL Aug 5, 2026Material review Oct 30, 2026

Upstream Advisory

Key facts

Risk: Critical · CVSS 9.8
Exploitation: Not marked as known exploited
Affected software: 11 mapped packages or products
Fix availability: Available

Why this deserves its current priority

CVSS is 9.8. The current sources do not mark it as known exploited. Treat this as a source-backed prioritization signal, not a statement about your environment.

Analysis status

Analysis pending evidence review

Factual feed record only; HOL analysis is not approved for indexing. Read the methodology.

Affected scope and exposure questions

The current feed maps Linux/Linux (generic), Linux/Linux (generic), Linux/Linux (generic). Check affected ranges and fixed versions before updating.

Affected products and reported versions
Product	Affected versions	Fixed versions
cpe:2.3:o:linux:linux_kernel::::::::	Not reported	Not reported
cpe:2.3:o:linux:linux_kernel:6.13:rc1::::::	Not reported	Not reported
cpe:2.3:o:linux:linux_kernel:6.13:rc2::::::	Not reported	Not reported
cpe:2.3:o:linux:linux_kernel:6.13:rc3::::::	Not reported	Not reported
cpe:2.3:o:linux:linux_kernel:6.13:rc4::::::	Not reported	Not reported
cpe:2.3:o:linux:linux_kernel:6.13:rc5::::::	Not reported	Not reported
cpe:2.3:o:linux:linux_kernel:6.13:rc6::::::	Not reported	Not reported
cpe:2.3:o:linux:linux_kernel:6.13:rc7::::::	Not reported	Not reported

Mapped affected packages and fixed versions
Package	Affected range	Fixed version
Linux/Linuxgeneric	>=7be3248f313930ff3d3436d4e9ddbe9fccc1f541 <1ea68070338518a1d31ce71e6abfe1b30001b27a \|\| >=7be3248f313930ff3d3436d4e9ddbe9fccc1f541 <a2be5f2ba34d0c6d5ef2624b24e3d852561fcd6a \|\| >=7be3248f313930ff3d3436d4e9ddbe9fccc1f541 <fa2f9906a7b333ba757a7dbae0713d8a5396186e \|\| 49f933bb3016269dc50074eac5f6033d127644f1 \|\| 1c35a216ef77db708178ca225d796271f2f60a7a \|\| >=5.14.19 <5.15 \|\| >=5.15.3 <5.16	1ea68070338518a1d31ce71e6abfe1b30001b27a, a2be5f2ba34d0c6d5ef2624b24e3d852561fcd6a, fa2f9906a7b333ba757a7dbae0713d8a5396186e, 5.15, 5.16
Linux/Linuxgeneric	5.16	Not reported
Linux/Linuxgeneric	>=7be3248f313930ff3d3436d4e9ddbe9fccc1f541 <35455f6c9326a8d10e91f3d5ba9260ab795b7d9a \|\| >=7be3248f313930ff3d3436d4e9ddbe9fccc1f541 <1ea68070338518a1d31ce71e6abfe1b30001b27a \|\| >=7be3248f313930ff3d3436d4e9ddbe9fccc1f541 <a2be5f2ba34d0c6d5ef2624b24e3d852561fcd6a \|\| >=7be3248f313930ff3d3436d4e9ddbe9fccc1f541 <fa2f9906a7b333ba757a7dbae0713d8a5396186e \|\| 49f933bb3016269dc50074eac5f6033d127644f1 \|\| 1c35a216ef77db708178ca225d796271f2f60a7a \|\| >=5.14.19 <5.15 \|\| >=5.15.3 <5.16	35455f6c9326a8d10e91f3d5ba9260ab795b7d9a, 1ea68070338518a1d31ce71e6abfe1b30001b27a, a2be5f2ba34d0c6d5ef2624b24e3d852561fcd6a, fa2f9906a7b333ba757a7dbae0713d8a5396186e, 5.15, 5.16

Recommended response

Check inventory. Check lockfiles and deployed manifests for Linux/Linux, Linux/Linux, Linux/Linux.
Review the reported fix. Update Linux/Linux to 1ea68070338518a1d31ce71e6abfe1b30001b27a; Linux/Linux to 35455f6c9326a8d10e91f3d5ba9260ab795b7d9a if you use the affected versions. Test the change in a non-production environment first.

Evidence timeline and material changes

Published upstream
Jan 31, 2025
Evidence: source:cvelist:source_dates:source-dates:record
Source modified
Oct 30, 2026
Evidence: source:cvelist:source_dates:source-dates:record
First seen by HOL
Aug 5, 2026

Sources and claim methodology

Upstream source description

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: <TASK> ? 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+0x223/0x3c0 ? exc_invalid_op+0x4e/0x70 ? __slab_free+0x223/0x3c0 ? asm_exc_invalid_op+0x16/0x20 ? __slab_free+0x223/0x3c0 ? extract_hostname+0x5c/0xa0 [cifs] ? extract_hostname+0x5c/0xa0 [cifs] ? __kmalloc+0x4b/0x140 __reconnect_target_unlocked+0x3e/0x160 [cifs] reconnect_dfs_server+0x145/0x430 [cifs] cifs_handle_standard+0x1ad/0x1d0 [cifs] cifs_demultiplex_thread+0x592/0x730 [cifs] ? __pfx_cifs_demultiplex_thread+0x10/0x10 [cifs] kthread+0xdd/0x100 ? __pfx_kthread+0x10/0x10 ret_from_fork+0x29/0x50 </TASK>

Quoted source text, attributed separately from HOL analysis.