CVE-2026-74653 (GCVE-0-2026-74653)

Vulnerability from cvelistv5 – Published: 2026-08-22 15:32 – Updated: 2026-08-27 12:39
VLAI
Title
serial: 8250_of: clear stuck empty-FIFO RX-timeout on LPC32xx
Summary
In the Linux kernel, the following vulnerability has been resolved: serial: 8250_of: clear stuck empty-FIFO RX-timeout on LPC32xx The NXP LPC32xx UART (PORT_LPC3220) can latch an RX character-timeout interrupt while the RX FIFO is empty: IIR reports UART_IIR_RX_TIMEOUT (0x0c) but LSR.DR is clear. A character timeout is only cleared by reading RHR, but serial8250_rx_chars() reads RHR only when LSR.DR is set, so nothing ever clears the condition. The interrupt is level-triggered and re-fires immediately, so on a single-core ARM926 the resulting interrupt storm livelocks the CPU. It is reproducible when userspace repeatedly opens the front-panel port (ttyS1): serial8250_do_set_termios() re-enables interrupts on unlock and the handler then spins forever with iir=0xcc lsr=0x60 ier=0x05, tripping the soft-lockup detector in serial8250_handle_irq_locked(). LPC32xx has no dedicated 8250 glue driver, it's driven by the generic 8250_of. Add a hardware specific handle_irq for PORT_LPC3220, wired up in of_platform_serial_setup() the same way fsl8250_handle_irq is installed. The handler follows dw8250_handle_irq(): on an RX timeout with an empty FIFO (LSR.DR and LSR.BI clear) it does one throwaway RHR read to clear the condition, then calls serial8250_handle_irq_locked(). No real received data is ever discarded, and it is a no-op on healthy UARTs which never report a timeout with DR clear. This is the same class of bug already worked around in other 8250 drivers; see commit 424d79183af0 ("serial: 8250_dw: Avoid "too much work" from bogus rx timeout interrupt") which reports the identical iir=0xcc/lsr=0x60. See also UART_RX_TIMEOUT_QUIRK in 8250_omap, and the note in 8250_bcm7271.
Severity
No CVSS data available.
Assigner
References
Impacted products
Vendor Product Version CPE status
Linux Linux Affected: e6e912c4964ce5976e508881207dfa96d5f856d7 , < c321dc5172c8c66e21ffbeeb7a2ebb88ae6fd4c3 (git)
Affected: e6e912c4964ce5976e508881207dfa96d5f856d7 , < 3ce24bc4d115336218e59b7e286fd3a79f4fc4c6 (git)
Affected: e6e912c4964ce5976e508881207dfa96d5f856d7 , < 7795e8abedc86438cae0454602cbf9038b94bf38 (git)
Affected: e6e912c4964ce5976e508881207dfa96d5f856d7 , < 1423415471274abda87024967d7fe2206ceee0ea (git)
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Linux Linux Affected: 2.6.36
Unaffected: 0 , < 2.6.36 (semver)
Unaffected: 6.12.106 , ≤ 6.12.* (semver)
Unaffected: 6.18.45 , ≤ 6.18.* (semver)
Unaffected: 7.1.9 , ≤ 7.1.* (semver)
Unaffected: 7.2 , ≤ * (original_commit_for_fix)
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{
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      "affected": [
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          "product": "Linux",
          "programFiles": [
            "drivers/tty/serial/8250/8250_of.c"
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          "vendor": "Linux",
          "versions": [
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              "version": "0",
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              "versionType": "semver"
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              "status": "unaffected",
              "version": "6.18.45",
              "versionType": "semver"
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              "status": "unaffected",
              "version": "7.1.9",
              "versionType": "semver"
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              "status": "unaffected",
              "version": "7.2",
              "versionType": "original_commit_for_fix"
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      "cpeApplicability": [
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                  "vulnerable": true
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      "descriptions": [
        {
          "lang": "en",
          "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nserial: 8250_of: clear stuck empty-FIFO RX-timeout on LPC32xx\n\nThe NXP LPC32xx UART (PORT_LPC3220) can latch an RX character-timeout\ninterrupt while the RX FIFO is empty: IIR reports UART_IIR_RX_TIMEOUT\n(0x0c) but LSR.DR is clear. A character timeout is only cleared by\nreading RHR, but serial8250_rx_chars() reads RHR only when LSR.DR is\nset, so nothing ever clears the condition. The interrupt is\nlevel-triggered and re-fires immediately, so on a single-core ARM926\nthe resulting interrupt storm livelocks the CPU.\n\nIt is reproducible when userspace repeatedly opens the front-panel port\n(ttyS1): serial8250_do_set_termios() re-enables interrupts on unlock and\nthe handler then spins forever with iir=0xcc lsr=0x60 ier=0x05, tripping\nthe soft-lockup detector in serial8250_handle_irq_locked().\n\nLPC32xx has no dedicated 8250 glue driver, it\u0027s driven by the generic\n8250_of. Add a hardware specific handle_irq for PORT_LPC3220, wired up\nin of_platform_serial_setup() the same way fsl8250_handle_irq is\ninstalled. The handler follows dw8250_handle_irq(): on an RX timeout\nwith an empty FIFO (LSR.DR and LSR.BI clear) it does one throwaway RHR\nread to clear the condition, then calls serial8250_handle_irq_locked().\nNo real received data is ever discarded, and it is a no-op on healthy\nUARTs which never report a timeout with DR clear.\n\nThis is the same class of bug already worked around in other 8250 drivers;\nsee commit 424d79183af0 (\"serial: 8250_dw: Avoid \"too much work\" from bogus rx timeout interrupt\")\nwhich reports the identical iir=0xcc/lsr=0x60. See also\nUART_RX_TIMEOUT_QUIRK in 8250_omap, and the note in 8250_bcm7271."
        }
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      "providerMetadata": {
        "dateUpdated": "2026-08-27T12:39:55.086Z",
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        "shortName": "Linux"
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        },
        {
          "url": "https://git.kernel.org/stable/c/7795e8abedc86438cae0454602cbf9038b94bf38"
        },
        {
          "url": "https://git.kernel.org/stable/c/1423415471274abda87024967d7fe2206ceee0ea"
        }
      ],
      "title": "serial: 8250_of: clear stuck empty-FIFO RX-timeout on LPC32xx",
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    "datePublished": "2026-08-22T15:32:28.521Z",
    "dateReserved": "2026-08-15T05:44:03.923Z",
    "dateUpdated": "2026-08-27T12:39:55.086Z",
    "state": "PUBLISHED"
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      "date": "2026-09-23",
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      "percentile": "0.06473"
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      "cve": "CVE-2026-74653",
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      "initial_release_date": "2026-08-24T01:06:36.000Z",
      "product_status:known_affected": "2",
      "source": "Microsoft CSAF VEX",
      "status": "final",
      "title": "serial: 8250_of: clear stuck empty-FIFO RX-timeout on LPC32xx",
      "url": "https://msrc.microsoft.com/csaf/vex/2026/msrc_cve-2026-74653.json",
      "version": "3"
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        "descriptions": [
          {
            "lang": "en",
            "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nserial: 8250_of: clear stuck empty-FIFO RX-timeout on LPC32xx\n\nThe NXP LPC32xx UART (PORT_LPC3220) can latch an RX character-timeout\ninterrupt while the RX FIFO is empty: IIR reports UART_IIR_RX_TIMEOUT\n(0x0c) but LSR.DR is clear. A character timeout is only cleared by\nreading RHR, but serial8250_rx_chars() reads RHR only when LSR.DR is\nset, so nothing ever clears the condition. The interrupt is\nlevel-triggered and re-fires immediately, so on a single-core ARM926\nthe resulting interrupt storm livelocks the CPU.\n\nIt is reproducible when userspace repeatedly opens the front-panel port\n(ttyS1): serial8250_do_set_termios() re-enables interrupts on unlock and\nthe handler then spins forever with iir=0xcc lsr=0x60 ier=0x05, tripping\nthe soft-lockup detector in serial8250_handle_irq_locked().\n\nLPC32xx has no dedicated 8250 glue driver, it\u0027s driven by the generic\n8250_of. Add a hardware specific handle_irq for PORT_LPC3220, wired up\nin of_platform_serial_setup() the same way fsl8250_handle_irq is\ninstalled. The handler follows dw8250_handle_irq(): on an RX timeout\nwith an empty FIFO (LSR.DR and LSR.BI clear) it does one throwaway RHR\nread to clear the condition, then calls serial8250_handle_irq_locked().\nNo real received data is ever discarded, and it is a no-op on healthy\nUARTs which never report a timeout with DR clear.\n\nThis is the same class of bug already worked around in other 8250 drivers;\nsee commit 424d79183af0 (\"serial: 8250_dw: Avoid \"too much work\" from bogus rx timeout interrupt\")\nwhich reports the identical iir=0xcc/lsr=0x60. See also\nUART_RX_TIMEOUT_QUIRK in 8250_omap, and the note in 8250_bcm7271."
          }
        ],
        "id": "CVE-2026-74653",
        "lastModified": "2026-08-27T13:18:35.877",
        "metrics": {},
        "published": "2026-08-22T16:16:38.827",
        "references": [
          {
            "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
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        "sourceIdentifier": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
        "vulnStatus": "Received"
      }
    },
    "redhat_vex": {
      "aggregate_severity": "Low",
      "current_release_date": "2026-08-25T10:02:38+00:00",
      "cve": "CVE-2026-74653",
      "id": "CVE-2026-74653",
      "initial_release_date": "2026-08-22T00:00:00+00:00",
      "product_status:known_affected": "232",
      "product_status:known_not_affected": "42",
      "source": "Red Hat CSAF VEX",
      "status": "final",
      "title": "kernel: serial: 8250_of: clear stuck empty-FIFO RX-timeout on LPC32xx",
      "url": "https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-74653.json",
      "version": "3"
    },
    "suse_vex": {
      "aggregate_severity": "moderate",
      "current_release_date": "2026-09-15T01:17:18Z",
      "cve": "CVE-2026-74653",
      "id": "CVE-2026-74653",
      "initial_release_date": "2026-08-23T00:05:11Z",
      "product_status:known_affected": "357",
      "source": "SUSE CSAF VEX",
      "status": "interim",
      "title": "SUSE CVE CVE-2026-74653",
      "url": "https://ftp.suse.com/pub/projects/security/csaf-vex/cve-2026-74653.json",
      "version": "7"
    }
  }
}



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Forecast uses a logistic model when the trend is rising, or an exponential decay model when the trend is falling. Fitted via linearized least squares.

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  • Not patched: The vulnerability was not observed as successfully patched by the user who reported the sighting.



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