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CVE.org (no NVD analysis yet)· CNA Linux

CVE-2026-99126: s390/ctcm: Prevent XID null dereference

Noroxi assessment

Priority: Monitor (action score 0/100)

  • The sources we track (CISA KEV, Exploit-DB, Metasploit, Nuclei, GitHub) show no public exploit code or exploitation in the wild.
  • Probability of exploitation in the next 30 days: 0.17% (FIRST EPSS).
  • Fixed version: Linux Linux 1525fb6e2f9f9a2c8c8723ee0959b1130a6b8213, 34fa3607b7604b3052b19cec8b0ad644818cdd2a, 8a2f7a4ad1d81612fa65bfa4d392ba1bb2f5eeab; azl3 kernel 6.6.157.1-1 on Azure Linux 3.0 Release Notes; azl3 kernel 6.6.159.1-1 on Azure Linux 3.0 Release Notes.
  • Mentioned 1 time in Turkish national cyber security advisories (siberguvenlik.gov.tr).

Low priority for now. Upgrade to Linux Linux 1525fb6e2f9f9a2c8c8723ee0959b1130a6b8213, 34fa3607b7604b3052b19cec8b0ad644818cdd2a, 8a2f7a4ad1d81612fa65bfa4d392ba1bb2f5eeab; azl3 kernel 6.6.157.1-1 on Azure Linux 3.0 Release Notes; azl3 kernel 6.6.159.1-1 on Azure Linux 3.0 Release Notes or later.

Generated automatically from the record's data: CVSS (NVD and CNA), CISA KEV and SSVC, FIRST EPSS, exploit sources, fixed versions. How we calculate it

Primary sources: NVD · CVE.org · FIRST EPSS

In the Linux kernel, the following vulnerability has been resolved: s390/ctcm: Prevent XID null dereference The mpc_validate_xid() function sets grp->saved_xid2->xid2_flag2 to 0x40 to signal XID validation error. If peer XID is NULL or r/w channel pairing mismatch happens, grp->saved_xid2 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->xid2_flag2 instead of grp->saved_xid2->xid2_flag2 for validation errors.

—No exploit Fix available
Published
Oct 28, 2026
Updated
Oct 30, 2026
EPSS
0.1% · 7th percentile
CWE
—

Report tools

JSON

Action score

0

Monitor

Low priority for now.

CVSS
0 / 40 · —
CISA KEV
0 / 30 · Not listed
EPSS
0 / 30 · 0.1%

Get told when this record changes

  • Not in KEV: no record of exploitation in the wild
  • No public exploit code on record
  • A fix has been released

If any of these changes, we'll tell you in the daily email digest.

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When you'll hear from us

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  • when exploit code appears or is weaponized
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  • when EPSS rises 20 points in a week

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Noroxi analysis

What does it mean in your environment?

The assessment above is generated automatically from the record's data; it doesn't know your environment. Our team verifies on your systems whether this vulnerability is actually exploitable and which mitigation is enough.

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Affected systems

Is your version affected?

Pick the product and type the version you run. It's compared with this record's version ranges in your browser; the version isn't sent anywhere.

—

Versions reported by the vendor

Affected version ranges reported by the assigning authority (Linux). Independent of NVD's CPE analysis and usually ahead of it.

  • Linux Linux

    • 2.6.26affected
    • 293d984f0e3604c04dcdbf00117ddc1e5d4b1909 and later · before f9d9e2dadc9fbdfe01aeb6581978c3b59092919eaffected · git
    • 293d984f0e3604c04dcdbf00117ddc1e5d4b1909 and later · before a7c3e1795e4fe5e6680cab7cd7eee0503b00a248affected · git
    • 293d984f0e3604c04dcdbf00117ddc1e5d4b1909 and later · before c11e435d334e4c311eaaf721e179a5ca6852c221affected · git
    • 293d984f0e3604c04dcdbf00117ddc1e5d4b1909 and later · before 977dac6cc5531a8e058df05b6af94406b940cb9eaffected · git
    • 293d984f0e3604c04dcdbf00117ddc1e5d4b1909 and later · before 1525fb6e2f9f9a2c8c8723ee0959b1130a6b8213affected · git
    • 293d984f0e3604c04dcdbf00117ddc1e5d4b1909 and later · before 34fa3607b7604b3052b19cec8b0ad644818cdd2aaffected · git
    • 293d984f0e3604c04dcdbf00117ddc1e5d4b1909 and later · before 8a2f7a4ad1d81612fa65bfa4d392ba1bb2f5eeabaffected · git
    • 293d984f0e3604c04dcdbf00117ddc1e5d4b1909 and later · before b264d8422779d69febce914efc47a92a85cc382caffected · git
    • before 2.6.26not affected · semver

Package-level exposure

OSV and GitHub Advisory data: ecosystem, package and range. SBOM matching uses this table.

EcosystemPackageAffected rangeFix
Debian:12linuxfrom 0—
Debian:13linuxbefore 6.12.115-26.12.115-2

Same product

linux: all records

Other highest-scoring records for the same primary product.

  • CVE-2026-74705udp: fix potential use-after-free in tunnel segmentation
    40Plan
  • CVE-2026-74612veth: fix skb length accounting after XDP frag adjustment
    40Plan
  • CVE-2026-74475vxlan: use neigh_ha_snapshot() in route_shortcircuit()
    40Plan

Published before and after this one in the same product

  • ← EarlierCVE-2026-99124Oct 28, 2026 · s390/pci: Fix leak of uninitialized kernel data in SCLP report
    0Monitor
  • ← EarlierCVE-2026-99125Oct 28, 2026 · s390/pai: Handle multiple PMU stop callback invocations
    0Monitor
  • Later →CVE-2026-99127Oct 28, 2026 · page_pool: keep frag_offset aligned for odd-sized requests
    0Monitor

Remediation

Which version to upgrade to

Fix versions compiled from the vendor, package registries and Microsoft. Verify the vendor's note before upgrading.

Product / packageFixed versionSource
Linux Linux1525fb6e2f9f9a2c8c8723ee0959b1130a6b8213Vendor (CNA)
Linux Linux34fa3607b7604b3052b19cec8b0ad644818cdd2aVendor (CNA)
Linux Linux8a2f7a4ad1d81612fa65bfa4d392ba1bb2f5eeabVendor (CNA)
Linux Linux977dac6cc5531a8e058df05b6af94406b940cb9eVendor (CNA)
Linux Linuxa7c3e1795e4fe5e6680cab7cd7eee0503b00a248Vendor (CNA)
Linux Linuxb264d8422779d69febce914efc47a92a85cc382cVendor (CNA)
Linux Linuxc11e435d334e4c311eaaf721e179a5ca6852c221Vendor (CNA)
Linux Linuxf9d9e2dadc9fbdfe01aeb6581978c3b59092919eVendor (CNA)
azl3 kernel 6.6.157.1-1 on Azure Linux 3.0Release NotesMicrosoft (MSRC)
azl3 kernel 6.6.159.1-1 on Azure Linux 3.0Release NotesMicrosoft (MSRC)
debian:linux6.12.115-2 · Debian:13Package registry (OSV)

Exploit status

No known public exploit

No public exploit has been observed yet. That doesn't mean you're safe, only that the bar is a little higher.

Research context

For pentesters and researchers: attack profile, score disagreement, timeline, patch commits, credits, variant and chain candidates, bug bounty scope. All derived from existing data; no exploit code.

Timeline

From publication to today: proof of concept, Metasploit module, CISA KEV and fix record. Dates are as reported by the sources.

  1. Published
  2. Fix recordedsame day
  3. TodayNov 7, 2026+10 d
EPSS, last 120 days

FIRST EPSS daily score; only changes of 0.01 or more are recorded (step chart).

Patch and commit links

Commit, PR and diff links among the references. A starting point for patch-diffing and variant hunting; fixes, not exploits.

No commit or PR link among the references.

Credits

All researchers

Finders, reporters and analysts named in the CNA record. Click a name for that researcher’s other records.

No credits in the CNA record.

Variant candidates

Same product, same weakness class, within 18 months. If the patch missed the root cause, the sibling bug is here.

No nightly-computed relations.

Chain candidates

An authentication bypass and a privilege-requiring bug in the same product, published close together: combined they may become an unauthenticated path.

—

Bug bounty scope

No known public program.

Source: bounty-targets-data (public HackerOne, Bugcrowd, Intigriti, YesWeHack listings).

National notice (Türkiye Cybersecurity Directorate / USOM)

Official security notices citing this record; remediation advice is on the agency's page.

All national notices →

Technical details

No CVSS vector for this record, so attack conditions can't be derived.

Weakness class (CWE)

—

Attack context

MITRE CAPEC attack patterns and ATT&CK techniques for this weakness class (CWE). A starting point for detection rules and threat hunting.

MITRE has no CAPEC/ATT&CK mapping for this CWE.

Change log

  1. Exploit maturity— → none
  2. Fix✗ → ✓

For records you follow, these changes also arrive as notifications. →

References

Show all references (7 more)

Vendor advisories and official records. Exploit/PoC links are deliberately left out.

All records