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

CVE-2026-99133: net/iucv: fix the recvmsg window update

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: 0.18% (FIRST EPSS).
  • Fixed version: Linux Linux 01123990f59ce32a1a5e690a4aeee002e932bb07, 1ebe68bbf8e75eeccaca0c7bc9694f5bc0c3f00a, 23e7fbbdca5aaba2a9a7bb9e4f2dc179c290ee76; 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 6.6.161.1-1.
  • Mentioned 1 time in Turkish national cyber security advisories (siberguvenlik.gov.tr).

Low priority for now. Upgrade to Linux Linux 01123990f59ce32a1a5e690a4aeee002e932bb07, 1ebe68bbf8e75eeccaca0c7bc9694f5bc0c3f00a, 23e7fbbdca5aaba2a9a7bb9e4f2dc179c290ee76; 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 6.6.161.1-1 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: net/iucv: fix the recvmsg window update iucv_sock_recvmsg() sends the HiperSockets-only AF_IUCV_FLAG_WIN without testing the transport, so on a classic z/VM socket iucv_send_ctrl() sizes the skb through a NULL iucv->hs_dev. SO_MSGLIMIT accepts 1, so msglimit / 2 is zero and one recvmsg() on its own socket is enough for an unprivileged process to take a spurious disconnect. It also calls iucv_send_ctrl() under spin_lock_bh(&message_q.lock), which allocates GFP_KERNEL inside a section the code treats as atomic. Sending outside that lock lets two recvmsg() reach afiucv_hs_send() at once, where msg_recv is sampled for the advertised window and subtracted after dev_queue_xmit() -- and sendmsg reaches that counter under lock_sock() while recvmsg holds no socket lock, so both can subtract the same value, the counter goes negative and the credit reaches the peer twice. Test the transport, claim the credit with atomic_xchg() after the last error exit and hand it back if the transmit fails, and send once the lock is dropped.

—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%

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

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Noroxi analysis

What does it mean in your environment?

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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

    • 3.2affected
    • 3881ac441f642d56503818123446f7298442236b and later · before 01123990f59ce32a1a5e690a4aeee002e932bb07affected · git
    • 3881ac441f642d56503818123446f7298442236b and later · before 1ebe68bbf8e75eeccaca0c7bc9694f5bc0c3f00aaffected · git
    • 3881ac441f642d56503818123446f7298442236b and later · before 23e7fbbdca5aaba2a9a7bb9e4f2dc179c290ee76affected · git
    • 3881ac441f642d56503818123446f7298442236b and later · before ce8aac3eb57f5366fa082b7cb8a1ac5652274f37affected · git
    • 3881ac441f642d56503818123446f7298442236b and later · before 8f2efa742f4cfe7dd756154f8bc07350dbe3ec92affected · git
    • 3881ac441f642d56503818123446f7298442236b and later · before fe7393a627db2d093e8c0cae69d619b30fefae5faffected · git
    • 3881ac441f642d56503818123446f7298442236b and later · before fa5acd038ea657ad5033713d6916214cbd349151affected · git
    • before 3.2not affected · semver
    • 5.15.224 and later · up to and including 5.15.*not 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-2026-99131Oct 28, 2026 · xfs: fix capability check in xfs
    32Monitor
  • ← EarlierCVE-2026-99132Oct 28, 2026 · xfs: don't hold buffer locks across sync transaction commit in xfs_sync_sb_buf
    0Monitor
  • Later →CVE-2026-99134Oct 28, 2026 · mac802154: fix data race and NULL deref on local->assoc_dev
    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 Linux01123990f59ce32a1a5e690a4aeee002e932bb07Vendor (CNA)
Linux Linux1ebe68bbf8e75eeccaca0c7bc9694f5bc0c3f00aVendor (CNA)
Linux Linux23e7fbbdca5aaba2a9a7bb9e4f2dc179c290ee76Vendor (CNA)
Linux Linux8f2efa742f4cfe7dd756154f8bc07350dbe3ec92Vendor (CNA)
Linux Linuxce8aac3eb57f5366fa082b7cb8a1ac5652274f37Vendor (CNA)
Linux Linuxfa5acd038ea657ad5033713d6916214cbd349151Vendor (CNA)
Linux Linuxfe7393a627db2d093e8c0cae69d619b30fefae5fVendor (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 3.06.6.161.1-1 · Release 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 (6 more)

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

All records