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CVE-2026-31392

Medium

Elevated severity or exploit probability.

CVSS base
8.1 HIGH
CVSS:3.1/AV:L/AC:L/PR:H/UI:N/S:C/C:H/I:H/A:L
EPSS — probability of exploitation (30 days)
0.1%
2.3th percentile
CISA KEV
Not listed
Weakness / dates
—
Published 2026-04-03 · modified 2026-07-21

CVSS breakdown

CVSS:3.1/AV:L/AC:L/PR:H/UI:N/S:C/C:H/I:H/A:L

Attack VectorLLocal
Attack ComplexityLLow
Privileges RequiredHHigh
User InteractionNNone
ScopeCChanged
ConfidentialityHHigh
IntegrityHHigh
AvailabilityLLow

Timeline

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 ```

Affected

linux

References

Official: NVD · CVE.org