Vulnerability · CVE-2026-99203

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

Published Oct 28, 2026 · catalog updated Nov 1, 2026 · Linux Linux

Last checked Nov 4, 2026. A connected source was read within the last 7 days.

Check if you run it

No confirmed exploitation is on record for CVE-2026-99203. EPSS is 0.12%. Act only if a listed version of Linux Linux is installed.

Gaps on this record

No vendor fix or required action is stored. Compare the linked advisory before you change production.

Same product and reporting

CVE-2026-99260 · Medium
CVE-2026-99259 · Medium
CVE-2026-99258 · High
CVE-2026-99257 · Medium
CVE-2026-99255 · Medium

Severity: High7.8
Known exploitation: Not in CISA/VulnCheck KEV
EPSS: 0.12%
Remediation: Advisory link
Affected products: Debian:12 linux · Debian:13 linux · Debian:14 linux · Linux Kernel · Ubuntu:16.04:LTS linux-hwe-edge · Ubuntu:Pro:14.04:LTS linux

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.

Are you affected?

Enter the version you run. The result uses only the ranges stored on this record.

The check returns affected, not affected, or incomplete. It does not guess a version that is missing from the record.

Debian:12 linux6.1.106-1, 6.1.106-2, 6.1.106-3
Debian:13 linux6.12.100-1, 6.12.101-1, 6.12.105-1
Debian:14 linux6.12.100-1, 6.12.101-1, 6.12.105-1
Linux Kernel2.6.30 → 5.10.273; 5.11.0 → 5.15.224; 5.16.0 → 6.1.191
Linux Kernel2.6.30 → 6.18.59; 6.19.0 → 7.2.13
Ubuntu:16.04:LTS linux-hwe-edge4.8.0-28.30~16.04.1, 4.8.0-30.32~16.04.1, 4.8.0-32.34~16.04.1
Ubuntu:Pro:14.04:LTS linux3.11.0-12.19, 3.12.0-1.3, 3.12.0-2.5
Ubuntu:Pro:14.04:LTS linux-aws4.4.0-1002.2, 4.4.0-1003.3, 4.4.0-1005.5
Ubuntu:Pro:14.04:LTS linux-azure4.15.0-1023.24~14.04.1, 4.15.0-1030.31~14.04.1, 4.15.0-1031.32~14.04.1
Ubuntu:Pro:14.04:LTS linux-lts-xenial4.4.0-13.29~14.04.1, 4.4.0-14.30~14.04.2, 4.4.0-15.31~14.04.1
Ubuntu:Pro:16.04:LTS linux4.2.0-16.19, 4.2.0-17.21, 4.2.0-19.23
Ubuntu:Pro:16.04:LTS linux-aws4.4.0-1001.10, 4.4.0-1003.12, 4.4.0-1004.13
Ubuntu:Pro:16.04:LTS linux-aws-hwe4.15.0-1030.31~16.04.1, 4.15.0-1031.33~16.04.1, 4.15.0-1032.34~16.04.1
Ubuntu:Pro:16.04:LTS linux-azure4.11.0-1009.9, 4.11.0-1011.11, 4.11.0-1013.13
Ubuntu:Pro:16.04:LTS linux-gcp4.10.0-1004.4, 4.10.0-1006.6, 4.10.0-1007.7
Ubuntu:Pro:16.04:LTS linux-hwe4.8.0-36.36~16.04.1, 4.8.0-39.42~16.04.1, 4.8.0-41.44~16.04.1
Ubuntu:Pro:16.04:LTS linux-kvm4.4.0-1004.9, 4.4.0-1007.12, 4.4.0-1008.13
linux kernelversion unspecified
vendor Linux Linuxversion unspecified

How to fix CVE-2026-99203

Upgrade
CVE-2026-99203 lists a fix boundary at 5.10.273. Compare the installed build with that boundary before you change production.
Version check
Seen in 6.1.106-1 · 13 other packages on the advisory
Advisory
Open the bsi record and follow its fix.
Official advisories

What to do

Three questions, each answered from this record only. Confirm the vendor advisory before you patch.

Should you patch?

No confirmed exploitation is on record for CVE-2026-99203. EPSS is 0.12%. Act only if a listed version of Linux Linux is installed.

Which versions are affected?

Compare what you have installed with Kernel 2.6.30 → 5.10.273; 5.11.0 → 5.15.224; 5.16.0 → 6.1.191; Kernel 2.6.30 → 6.18.59; 6.19.0 → 7.2.13. Compare the installed version with the linked vendor advisory before you change production.

What should an analyst verify?

No weakness class is stored. EPSS 0.12%. There is no CISA KEV listing. No Exploit-DB or Metasploit reference is linked. Use the source links for the original advisory.

Technology hubs

Debian security Ubuntu security

Code

The project this record applies to. Exploit listings stay in References.

Timeline

Detection, updates, and resolution for this record.

Oct 28, 2026 · Tenable CVE Database
Detected
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 ent
Oct 28, 2026 · Trivy Vulnerability DB
Updated
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 ent
Oct 29, 2026 · OpenSSF OSV / OSV Scanner
Fix available
Kernel fixed in 6.18.59; Kernel fixed in 7.2.13
Oct 29, 2026 · OpenSSF OSV / OSV Scanner
Fix available
Kernel fixed in 6.18.59; 6.19.0
Oct 29, 2026 · OpenSSF OSV / OSV Scanner
Updated
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 ent
Oct 30, 2026 · OpenSSF OSV / OSV Scanner
Updated
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 ent
Nov 1, 2026 · OpenSSF OSV / OSV Scanner
Fix available
Kernel fixed in 5.10.273; Kernel fixed in 5.15.224; Kernel fixed in 6.1.191; Kernel fixed in 6.6.161
Nov 1, 2026 · OpenSSF OSV / OSV Scanner
Fix available
Kernel fixed in 5.10.273; 5.11.0
Nov 1, 2026 · OpenSSF OSV / OSV Scanner
Updated
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 ent

Sources

BSI CERT-BundGovernment advisoryCVE-2026-99203
Linux Kernel: Mehrere Schwachstellen ermöglichen nicht spezifizierten Angriff
wid.cert-bund.de
CVE.orgVulnerability recordCVE-2026-99203
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 en
cve.org
FIRST EPSSExploitation probabilityCVE-2026-99203
30-day exploitation probability 0.12%
first.org
Linux Kernel CVEVendor advisoryCVE-2026-99203
From: Greg Kroah-Hartman Description =========== 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
git.kernel.org
OpenSSF OSV / OSV ScannerPackage advisoryCVE-2026-99203
pipe: preserve existing fasync readers on writer setup failure
osv.dev
OpenSSF OSV / OSV ScannerPackage advisoryUBUNTU-CVE-2026-99203
osv.dev
Tenable CVE DatabaseVulnerability recordCVE-2026-99203
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 ent
tenable.com
Trivy Vulnerability DBPackage advisoryDEBIAN-CVE-2026-99203
osv.dev

References

Freshness

Last verified in this catalog Nov 4, 2026. Significant claims (KEV, EPSS, CVSS, affected ranges) come from the source rows above — open the original publisher for the authoritative advisory.

FIRST EPSSNov 4, 2026
OpenSSF OSV / OSV ScannerNov 1, 2026
OpenSSF OSV / OSV ScannerOct 31, 2026
BSI CERT-BundOct 30, 2026
CVE.orgOct 29, 2026
Trivy Vulnerability DBOct 28, 2026
Linux Kernel CVEOct 28, 2026
Tenable CVE DatabaseOct 28, 2026

Priority score

24/100

Evidence confidence: High

A vendor or government advisory agrees with at least one other source.

Confirmed exploitation0/30
EPSS probability1/20
CVSS severity12/15
Public exploit0/10
Internet exposure6/10
Product prevalence5/5
Detection0/5
Threat research0/5

Decision signals

Four separate signals — do not infer one from another.

High

CVSS severity
7.8 v3.1
Technical impact. Separate from exploitation likelihood.
CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
EPSS probability
0.12% · p1.91%
Estimated probability of exploitation within 30 days (FIRST).
Known exploitation
No verified KEV listing
Evidence from CISA KEV or VulnCheck KEV only — not from EPSS alone.
Patch availability
Advisory link
A patch or advisory reference is linked. Open the original publisher for availability by product version.

Stacks

Debian Debian 12 Debian 13 Debian 14 Linux Ubuntu Ubuntu 14.04 Ubuntu 16.04

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