Use-after-free in Linux kernel pipe fasync handling on setup failure
Key facts
- Attack vector
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- Privileges required
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- User interaction
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- Attack complexity
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- Impact type
- —
- Confidentiality · integrity · availability
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- Fix status
- Partial Red Hat: 7 without a fix
No CVSS vector from any source. Fix status from CNA and Red Hat.
Summary
The Linux kernel from 2.6.30 is affected in its pipe fasync handling. When a duplicate fasync enable on an O_RDWR FIFO fails during allocation, the error path removes a pre-existing reader entry while the writer entry stays registered. An unprivileged local user under memory pressure can trigger a use-after-free in send_sigio() through this path.
Written with Claude Haiku 5.5 from the sources below · 2026-10-31
Description from the CNA
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.
Why it matters now
SSVC decision points
Not available: CISA has not published SSVC decision points for this record.
Affected products
| Vendor | Product | Affected versions | Fixed in | Status | Source |
|---|---|---|---|---|---|
| Linux | Linux | 2.6.30 and later | 5.10.273, 5.15.224, 6.1.191, 6.6.161, 6.12.115, 6.18.59, 7.2.13, 7.3 | Patch available | CNA |
- Linux VendorLinux Affected 2.6.30 and later Fixed in 5.10.273, 5.15.224, 6.1.191, 6.6.161, 6.12.115, 6.18.59, 7.2.13, 7.3 Patch available CNA
Remediation
Upgrade to Linux kernel 5.10.273, 5.15.224, 6.1.191, 6.6.161, 6.12.115, 6.18.59, 7.2.13 or 7.3. The sources list no fixed version for Red Hat Enterprise Linux 6, 7, 8, 9 and 10 or for Red Hat OpenShift Container Platform 4 and 5.
Written with Claude Haiku 5.5 from the sources below · 2026-10-31
- Fix · CNA Linux (Linux) Fixed in 5.10.273, 5.15.224, 6.1.191, 6.6.161, 6.12.115, 6.18.59, 7.2.13, 7.3
Vendor assessments
Red Hat
Red Hat rating: Moderate. Red Hat's page for this CVE →
| Product | Status | Plan or fix |
|---|---|---|
| Red Hat Enterprise Linux 10 | Affected | No fix yet: Fix deferred |
| Red Hat Enterprise Linux 6 | Affected | No fix planned: Out of support scope |
| Red Hat Enterprise Linux 7 | Affected | No fix yet: Fix deferred |
| Red Hat Enterprise Linux 8 | Affected | No fix yet: Fix deferred |
| Red Hat Enterprise Linux 9 | Affected | No fix yet: Fix deferred |
| Red Hat OpenShift Container Platform 4 | Affected | No fix yet: Fix deferred |
| Red Hat OpenShift Container Platform 5 | Affected | No fix yet: Fix deferred |
Timeline
- 2026-10-28 Threatist record created from CVE-2026-99203
- 2026-10-28 Alias added: GHSA-j875-7x9h-g92w
- 2026-10-29 Affected versions changed · Red Hat
- 2026-10-29 CVSS score added · Red Hat
- 2026-10-30 Fix available: Linux/Linux@22c7f57b0c0b0b8e19cfb41a1bd85f55715ad386, Linux/[email protected], Linux/[email protected] +7 · CNA
- 2026-10-30 5 new references · CNA
- 2026-10-31 Affected versions changed · Red Hat
References
Other 8
- https://git.kernel.org/stable/c/6041bcd185d4df051490fe166e64feae6c3b8291
- https://git.kernel.org/stable/c/7cdbfa22a7e270b155ddb958b1583a999c0c8abb
- https://git.kernel.org/stable/c/22c7f57b0c0b0b8e19cfb41a1bd85f55715ad386
- https://git.kernel.org/stable/c/94be790dd6fbe0912f35bb711bea8ef3687eaca9
- https://git.kernel.org/stable/c/9b0aa2a1d8df51f3dcb363c3a2d9531098e88dc6
- https://git.kernel.org/stable/c/4c42ce499ce4b1c787e61082e3b13df4f30c4eaa
- https://git.kernel.org/stable/c/2259809e5b7043c4ba20af7b14ba3e471cf55521
- https://git.kernel.org/stable/c/40bb03d3ea6f6a915218508819ecc4d7a7fa260d
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Sources
- CVE-2026-99203 · CVE Program
- CVE-2026-99203 · NVD
- FIRST EPSS
- GHSA-j875-7x9h-g92w · GitHub Advisory Database · CC BY 4.0
- CVE-2026-99203 · Red Hat security data · CC BY 4.0
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