What is CVE-2026-63883?

CVE-2026-63883 is a High severity Linux kernel vulnerability with a CVSS score of 7.3 out of 10, affecting Linux kernel versions from 6.3 onward and patched in 6.6.143, 6.12.93, 6.18.35 and others. CVE-2026-63883 has not been confirmed as actively exploited and is not listed in the CISA KEV catalog.

What is the CVSS score for CVE-2026-63883?

CVE-2026-63883 has a CVSS score of 7.3 out of 10, rated High severity. The vector string is CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:L.

Is there a patch available for CVE-2026-63883?

Yes, CVE-2026-63883 has been patched. Fixed versions include 6.6.143, 6.12.93, 6.18.35 and others. If you are running Linux kernel 6.3 or later up to the fix versions, apply the relevant patch for your kernel branch.

Is CVE-2026-63883 actively exploited?

CVE-2026-63883 has not been confirmed as actively exploited and is not listed in the CISA KEV catalog.

CVE-2026-63883

High

In the Linux kernel, the following vulnerability has been resolved: serial: qcom_geni: fix kfifo underflow when flush precedes DMA completion IRQ When uart_flush_buffer() runs before the DMA completion IRQ is delivered, the following race can occur (all steps serialized by uart_port_lock): 1. DMA starts: tx_remaining = N, kfifo contains N bytes 2. DMA completes in hardware; IRQ is pending but not yet delivered 3. uart_flush_buffer() acquires the port lock and calls kfifo_reset(), making kfifo_len() = 0 while tx_remaining remains N 4. uart_flush_buffer() releases the port lock 5. DMA IRQ fires; handle_tx_dma() acquires the port lock and calls uart_xmit_advance(uport, tx_remaining) on an empty kfifo uart_xmit_advance() increments kfifo->out by tx_remaining. Since kfifo_reset() already set both in and out to 0, out wraps past in, causing kfifo_len() to return UART_XMIT_SIZE - tx_remaining. The next start_tx_dma() call then submits a DMA transfer of stale buffer data. Fix this by snapshotting kfifo_len() at the start of handle_tx_dma() and skipping uart_xmit_advance() when fifo_len < tx_remaining, which indicates the kfifo was reset by a preceding flush.

Package Linux Kernel

Published 2026-07-19

Last modified 2026-07-27

CVSS version 3.1

Patch available

Yes

CVSS 3.1 score

7.3

out of 10

High

Attack Vector

Local

Attack Complexity

Low

Privileges Required

Low

User Interaction

None

Scope

Unchanged

Confidentiality

High

Integrity

High

Availability

Low

Vector string

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

Affected versions

Linux kernel versions 6.3 and later are affected. Fixed in 6.6.143, 6.12.93, 6.18.35, 7.0.12, 7.1 and their respective stable series.

Affected from

≥ 6.3

Fixed in

✓ 6.6.143 6.6.x ✓ 6.12.93 6.12.x ✓ 6.18.35 6.18.x ✓ 7.0.12 7.0.x ✓ 7.1

References

5 total

Details

CVE ID CVE-2026-63883

Severity High

CVSS score 7.3 / 10

CVSS version 3.1

Published 2026-07-19

Modified 2026-07-27

KEV No

Patch

Yes

Package linux

Frequently asked questions

What is CVE-2026-63883?

CVE-2026-63883 is a High severity Linux kernel vulnerability with a CVSS score of 7.3 out of 10 . It affects Linux kernel versions from 6.3 onward and has been patched in 6.6.143, 6.12.93, 6.18.35 and others. CVE-2026-63883 has not been confirmed as actively exploited and is not listed in the CISA KEV catalog.
What is the CVSS score for CVE-2026-63883?

CVE-2026-63883 has a CVSS score of 7.3 out of 10, rated High severity (CVSS 3.1). The vector string is CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:L.
Is there a patch available for CVE-2026-63883?

Yes. CVE-2026-63883 has been patched. Fixed versions include 6.6.143, 6.12.93, 6.18.35 and others. If you are running Linux kernel 6.3 or later up to the fix versions, apply the relevant patch for your kernel branch.
Is CVE-2026-63883 actively exploited?

No. CVE-2026-63883 has not been confirmed as actively exploited. It is not listed in the CISA Known Exploited Vulnerabilities (KEV) catalog.