DEBIAN-CVE-2026-99126: Debian/linux vulnerability

Published Oct 28, 2026

Updated

In the Linux kernel, the following vulnerability has been resolved: s390/ctcm: Prevent XID null dereference The mpcvalidatexid() function sets grp->savedxid2->xid2flag2 to 0x40 to signal XID validation error. If peer XID is NULL or r/w channel pairing mismatch happens, grp->savedxid2 is never initialized. An attempt to set the flag in such case leads to NULL dereference. Fix this by using the always available priv->xid->xid2flag2 instead of grp->savedxid2->xid2flag2 for validation errors.

Affected Software

3 affected components

debian/linux*

Event History

Oct 28, 2026

CVE Published

via OSV·11:17 AM

Data Sourced

via OSV·11:17 AM

DescriptionAffected Software

Frequently Asked Questions

What conditions can trigger the null dereference?

The issue can be triggered when the peer XID is NULL or when there is a read/write channel pairing mismatch. Under either condition, the saved XID structure may not have been initialized before the validation-error flag is written.

Which systems are realistically exposed?

Exposure is limited to Debian systems using the Linux kernel's s390 CTCM networking code. The provided information does not identify whether the affected configuration is enabled or used by default.

What does the fix change?

The fix records XID validation errors through priv->xid, which is always available, rather than through grp->saved_xid2, which may be NULL in the affected error paths.

DEBIAN-CVE-2026-99126: Debian/linux vulnerability

Affected Software

Event History

Frequently Asked Questions

What conditions can trigger the null dereference?

Which systems are realistically exposed?

What does the fix change?

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Frequently Asked Questions

What conditions can trigger the null dereference?

Which systems are realistically exposed?

What does the fix change?