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

CVE-2026-99203: pipe: preserve existing fasync readers on writer setup failure

Noroxi assessment

Priority: Monitor (action score 31/100)

  • 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: 0.12% (FIRST EPSS).
  • Someone with local access to the system can trigger it. A low-privileged account is enough. No user action is required. No special conditions are required; it is repeatable.
  • Fixed version: Linux Linux 2259809e5b7043c4ba20af7b14ba3e471cf55521, 22c7f57b0c0b0b8e19cfb41a1bd85f55715ad386, 40bb03d3ea6f6a915218508819ecc4d7a7fa260d; 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 2259809e5b7043c4ba20af7b14ba3e471cf55521, 22c7f57b0c0b0b8e19cfb41a1bd85f55715ad386, 40bb03d3ea6f6a915218508819ecc4d7a7fa260d; 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: pipe: preserve existing fasync readers on writer setup failure F_SETFL and FIOASYNC decide whether to invoke ->fasync() before pipe_fasync() takes pipe->mutex. Two enables of one O_RDWR FIFO can therefore both enter the callback. fasync_helper() allocates before checking for an existing entry. If the first enable installs both entries, a second enable can update the reader entry and then fail the allocation for the writer entry. The error path removes the pre-existing reader entry, clearing FASYNC while the writer entry remains registered. __fput() then skips ->fasync(), so a later pipe notification can dereference the freed file or its f_owner. An unprivileged memory-pressure reproducer triggers a KASAN slab-use-after-free in send_sigio() through this path. Keep the reader helper's result and undo the registration only if this call added it. The pipe mutex serializes changes to both lists, so a failed new registration still removes its reader, while a failed duplicate preserves the existing registrations and FASYNC. Successful duplicate enables continue to update fa_fd as before.

HighCVSS 7.8 · v3.1—No exploit Fix available
Published
Oct 28, 2026
Updated
Oct 31, 2026
EPSS
0.1% · 1th percentile
CWE
—

Report tools

JSON

Action score

31

Monitor

Low priority for now.

CVSS
31 / 40 · 7.8 / 10
CISA KEV
0 / 30 · Not listed
EPSS
0 / 30 · 0.1%

CNA vs NVD score

NVD
—
CNA · Linux
7.8
NVD has not scored this yet; the score shown is the CNA’s.

The score given by the assigning authority versus NVD’s independent score. A gap means the severity is contested.

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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?

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

    • 2.6.30affected
    • 76398425bb06b07cc3a3b1ce169c67dc9d6874ed and later · before 6041bcd185d4df051490fe166e64feae6c3b8291affected · git
    • 76398425bb06b07cc3a3b1ce169c67dc9d6874ed and later · before 7cdbfa22a7e270b155ddb958b1583a999c0c8abbaffected · git
    • 76398425bb06b07cc3a3b1ce169c67dc9d6874ed and later · before 22c7f57b0c0b0b8e19cfb41a1bd85f55715ad386affected · git
    • 76398425bb06b07cc3a3b1ce169c67dc9d6874ed and later · before 94be790dd6fbe0912f35bb711bea8ef3687eaca9affected · git
    • 76398425bb06b07cc3a3b1ce169c67dc9d6874ed and later · before 9b0aa2a1d8df51f3dcb363c3a2d9531098e88dc6affected · git
    • 76398425bb06b07cc3a3b1ce169c67dc9d6874ed and later · before 4c42ce499ce4b1c787e61082e3b13df4f30c4eaaaffected · git
    • 76398425bb06b07cc3a3b1ce169c67dc9d6874ed and later · before 2259809e5b7043c4ba20af7b14ba3e471cf55521affected · git
    • 76398425bb06b07cc3a3b1ce169c67dc9d6874ed and later · before 40bb03d3ea6f6a915218508819ecc4d7a7fa260daffected · git
    • before 2.6.30not 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-2026-99201Oct 28, 2026 · netlink: avoid hashing the network namespace pointer
    0Monitor
  • ← EarlierCVE-2026-99202Oct 28, 2026 · scsi: libsas: Fix SMP IO deadlock during HA resume
    0Monitor
  • Later →CVE-2026-99204Oct 28, 2026 · ocfs2/dlm: Protect the recovery list during debugfs reads
    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 Linux2259809e5b7043c4ba20af7b14ba3e471cf55521Vendor (CNA)
Linux Linux22c7f57b0c0b0b8e19cfb41a1bd85f55715ad386Vendor (CNA)
Linux Linux40bb03d3ea6f6a915218508819ecc4d7a7fa260dVendor (CNA)
Linux Linux4c42ce499ce4b1c787e61082e3b13df4f30c4eaaVendor (CNA)
Linux Linux6041bcd185d4df051490fe166e64feae6c3b8291Vendor (CNA)
Linux Linux7cdbfa22a7e270b155ddb958b1583a999c0c8abbVendor (CNA)
Linux Linux94be790dd6fbe0912f35bb711bea8ef3687eaca9Vendor (CNA)
Linux Linux9b0aa2a1d8df51f3dcb363c3a2d9531098e88dc6Vendor (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 3, 2026+6 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

Attack conditions

  • Someone with local access to the system can trigger it.
  • A low-privileged account is enough.
  • No user action is required.
  • No special conditions are required; it is repeatable.

If successful

Confidentiality
high · data can be read
Integrity
high · data or configuration can be modified
Availability
high · the service can be disrupted
Attack vector
Local
Attack complexity
Low
Privileges required
Low
User interaction
None
Scope
Unchanged
Confidentiality impact
High
Integrity impact
High
Availability impact
High

Weakness class (CWE)

—

CVSS vector

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

nvd-secondary

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. CVSS— → 7.8
  2. Severity— → high
  3. Exploit maturity— → none
  4. 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