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CVE-2026-31392— smb: client: fix krb5 mount with username option

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，该漏洞源于匹配会话时未验证用户名，可能导致使用错误凭据挂载共享。

CVSS 8.1 · High EPSS 0.17% · P6

Possible ATT&CK Techniques 1 AI

T1190 · Exploit Public-Facing Application

Affected Version Matrix 18

VendorProduct Version RangeStatus
Linux Linux 4ff67b720c02c36e54d55b88c2931879b7db1cd2< fd4547830720647d4af02ee50f883c4b1cca06e4 affected
4ff67b720c02c36e54d55b88c2931879b7db1cd2< 9229709ec8bf85ae7ca53aeee9aa14814cdc1bd2 affected
4ff67b720c02c36e54d55b88c2931879b7db1cd2< d33cbf0bf8979d779900da9be2505d68d9d8da25 affected
4ff67b720c02c36e54d55b88c2931879b7db1cd2< 9ee803bfdba0cf739038dbdabdd4c02582c8f2b2 affected
4ff67b720c02c36e54d55b88c2931879b7db1cd2< 6e9ff1eb7feedcf46ff2d0503759960ab58e7775 affected
4ff67b720c02c36e54d55b88c2931879b7db1cd2< 12b4c5d98cd7ca46d5035a57bcd995df614c14e1 affected
223c7f082d2836ac719b3b228bdcfab35e5e5330 affected
88720224330a655ab6268e20109b65b11cfd7f6a affected
… +10 more rows
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I. Basic Information for CVE-2026-31392

Vulnerability Information
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Vulnerability Title
smb: client: fix krb5 mount with username option
Source: CVE Program / CVE List V5
Vulnerability Description
In the Linux kernel, the following vulnerability has been resolved: smb: client: fix krb5 mount with username option Customer reported that some of their krb5 mounts were failing against a single server as the client was trying to mount the shares with wrong credentials. It turned out the client was reusing SMB session from first mount to try mounting the other shares, even though a different username= option had been specified to the other mounts. By using username mount option along with sec=krb5 to search for principals from keytab is supported by cifs.upcall(8) since cifs-utils-4.8. So fix this by matching username mount option in match_session() even with Kerberos. For example, the second mount below should fail with -ENOKEY as there is no 'foobar' principal in keytab (/etc/krb5.keytab). The client ends up reusing SMB session from first mount to perform the second one, which is wrong. ``` $ ktutil ktutil: add_entry -password -p testuser -k 1 -e aes256-cts Password for testuser@ZELDA.TEST: ktutil: write_kt /etc/krb5.keytab ktutil: quit $ klist -ke Keytab name: FILE:/etc/krb5.keytab KVNO Principal ---- ---------------------------------------------------------------- 1 testuser@ZELDA.TEST (aes256-cts-hmac-sha1-96) $ mount.cifs //w22-root2/scratch /mnt/1 -o sec=krb5,username=testuser $ mount.cifs //w22-root2/scratch /mnt/2 -o sec=krb5,username=foobar $ mount -t cifs | grep -Po 'username=\K\w+' testuser testuser ```
Source: CVE Program / CVE List V5
CVSS Information
CVSS:3.1/AV:L/AC:L/PR:H/UI:N/S:C/C:H/I:H/A:L
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，该漏洞源于匹配会话时未验证用户名，可能导致使用错误凭据挂载共享。
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 4ff67b720c02c36e54d55b88c2931879b7db1cd2 ~ fd4547830720647d4af02ee50f883c4b1cca06e4 -
Linux Linux 2.6.36 -

II. Public POCs for CVE-2026-31392

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III. Intelligence Information for CVE-2026-31392

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Same Patch Batch · Linux · 2026-04-03 · 71 CVEs total

CVE-2026-31402 9.8 CRITICAL nfsd: fix heap overflow in NFSv4.0 LOCK replay cache
CVE-2026-23450 9.8 CRITICAL net/smc: fix NULL dereference and UAF in smc_tcp_syn_recv_sock()
CVE-2026-23427 9.8 CRITICAL ksmbd: fix use-after-free in durable v2 replay of active file handles
CVE-2026-23428 9.8 CRITICAL ksmbd: fix use-after-free of share_conf in compound request
CVE-2026-23455 9.1 CRITICAL netfilter: nf_conntrack_h323: check for zero length in DecodeQ931()
CVE-2026-23425 8.8 HIGH KVM: arm64: Fix ID register initialization for non-protected pKVM guests
CVE-2026-23461 8.8 HIGH Bluetooth: L2CAP: Fix use-after-free in l2cap_unregister_user
CVE-2026-23462 8.8 HIGH Bluetooth: HIDP: Fix possible UAF
CVE-2026-23457 8.6 HIGH netfilter: nf_conntrack_sip: fix Content-Length u32 truncation in sip_help_tcp()
CVE-2026-23459 8.2 HIGH ip_tunnel: adapt iptunnel_xmit_stats() to NETDEV_PCPU_STAT_DSTATS
CVE-2026-23456 8.2 HIGH netfilter: nf_conntrack_h323: fix OOB read in decode_int() CONS case
CVE-2026-31393 8.1 HIGH Bluetooth: L2CAP: Validate L2CAP_INFO_RSP payload length before access
CVE-2026-31396 7.8 HIGH net: macb: fix use-after-free access to PTP clock
CVE-2026-23432 7.8 HIGH mshv: Fix use-after-free in mshv_map_user_memory error path
CVE-2026-31401 7.8 HIGH HID: bpf: prevent buffer overflow in hid_hw_request
CVE-2026-23458 7.8 HIGH netfilter: ctnetlink: fix use-after-free in ctnetlink_dump_exp_ct()
CVE-2026-23437 7.8 HIGH net: shaper: protect late read accesses to the hierarchy
CVE-2026-23444 7.8 HIGH wifi: mac80211: always free skb on ieee80211_tx_prepare_skb() failure
CVE-2026-23449 7.8 HIGH net/sched: teql: Fix double-free in teql_master_xmit
CVE-2026-23445 7.8 HIGH igc: fix page fault in XDP TX timestamps handling

Showing top 20 of 71 CVEs. View all on vendor page &rarr; →

IV. Related Vulnerabilities

Same product: Linux
Same vendor: Linux

V. Comments for CVE-2026-31392

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