CVE-2026-64191

HIGHPre-NVD 7.87.8—
EchelonGraph scoreMEDIUM confidence

This high-severity CVE scores 7.8 under a secondary CVSS source (NVD's own analysis pending). EPSS exploit probability: 0.2%, top 93% of all CVEs by exploit prediction. GitHub Security Advisory data not yet ingested — confidence will rise once GHSA publishes (typical lag: hours to days for open-source ecosystem CVEs; never for infrastructure-only CVEs).

Triggered by: NVD CVSS baseline
Sources: epss, secondary
Trending — 5 sources updated this week
7.8EG
EchelonGraph verdictPlan a fixSerious severity, but no confirmed exploitation yet.
  • High severity, but no confirmed exploitation yet
CISA-KEV: Not listedEPSS PROB: 0%CVSS: 7.8Exploit: None knownExposed: 0

No vendor fix yet — apply a workaround or compensating control (WAF / firewall / segmentation) and watch for a patch.

In the Linux kernel, the following vulnerability has been resolved:

i2c: stub: Reject I2C block transfers with invalid length

The I2C_SMBUS_I2C_BLOCK_DATA case in stub_xfer() uses data->block[0] as the transfer length. The existing check only clamps it to avoid overrunning the chip->words[256] register array, but does not validate it against I2C_SMBUS_BLOCK_MAX (32), which is the limit of the union i2c_smbus_data.block buffer (34 bytes total). The driver is a development/test tool (CONFIG_I2C_STUB=m, not built by default) that must be loaded with a chip_addr= parameter.

A local user with access to /dev/i2c-* can issue an I2C_SMBUS ioctl with I2C_SMBUS_I2C_BLOCK_DATA and data->block[0] > 32, causing stub_xfer() to read or write past the end of the union i2c_smbus_data.block buffer:

BUG: KASAN: stack-out-of-bounds in stub_xfer (drivers/i2c/i2c-stub.c:223) Read of size 1 at addr ffff88800abcfd92 by task exploit/81 Call Trace: stub_xfer (drivers/i2c/i2c-stub.c:223) __i2c_smbus_xfer (drivers/i2c/i2c-core-smbus.c:593) i2c_smbus_xfer (drivers/i2c/i2c-core-smbus.c:536) i2cdev_ioctl_smbus (drivers/i2c/i2c-dev.c:391) i2cdev_ioctl (drivers/i2c/i2c-dev.c:478) __x64_sys_ioctl (fs/ioctl.c:583) do_syscall_64 (arch/x86/entry/syscall_64.c:94) entry_SYSCALL_64_after_hwframe (arch/x86/entry/entry_64.S:130)

The bug exists because i2c-stub implements .smbus_xfer directly, bypassing the I2C_SMBUS_BLOCK_MAX validation in i2c_smbus_xfer_emulated(). The I2C_SMBUS_BLOCK_DATA case in the same function correctly validates against I2C_SMBUS_BLOCK_MAX, but the I2C_SMBUS_I2C_BLOCK_DATA case does not.

Fix by rejecting transfers with data->block[0] == 0 or data->block[0] > I2C_SMBUS_BLOCK_MAX with -EINVAL, consistent with both the I2C_SMBUS_BLOCK_DATA case in the same function and the I2C_SMBUS_I2C_BLOCK_DATA validation in i2c_smbus_xfer_emulated().

CVSS v3
7.8
EG Score
7.8(medium)
EG Risk
40(Track)
EG Risk 40/100SSVC: Track

EG Risk is EchelonGraph's 0–100 priority score: it fuses intrinsic severity with real-world exploitation and automatability so you can rank equal-severity CVEs and fix the most dangerous first. Higher = act sooner. Distinct from the 0–10 EG Score (severity).

How it’s computed
Severity78% × 45%
Exploitation0% × 40%
Automatability30% × 15%
Action: Routine — remediate on your standard cadence.
EPSS PROB
0%
EPSS %ILE
7%
KEV
Not listed

Published

July 20, 2026

Last Modified

July 27, 2026

Advisory Details (8)

Auto-updated Jul 27, 2026
No patch confirmed yet.
generic

i2c: stub: Reject I2C block transfers with invalid length - kernel/git/stable/linux.git - Linux kernel stable tree

https://git.kernel.org/stable/c/7e9072dbd5f2f17934751873450d2c22080ead80
generic

i2c: stub: Reject I2C block transfers with invalid length - kernel/git/stable/linux.git - Linux kernel stable tree

https://git.kernel.org/stable/c/6036b5067a8199ba7a2dc7b377d4b9dd276d5f9e
generic

i2c: stub: Reject I2C block transfers with invalid length - kernel/git/stable/linux.git - Linux kernel stable tree

https://git.kernel.org/stable/c/5f4d2bd028ebb6e4c09a9d64842546022321d4a7
generic

i2c: stub: Reject I2C block transfers with invalid length - kernel/git/stable/linux.git - Linux kernel stable tree

https://git.kernel.org/stable/c/4bd8635f28c135a08aac6badcd7d9b5cdb34335f
generic

i2c: stub: Reject I2C block transfers with invalid length - kernel/git/stable/linux.git - Linux kernel stable tree

https://git.kernel.org/stable/c/3fd225f3e4cd67ec8ddab1afed9da03c7c43537c
generic

i2c: stub: Reject I2C block transfers with invalid length - kernel/git/stable/linux.git - Linux kernel stable tree

https://git.kernel.org/stable/c/21e87f336ac6303fed54a69b1d0d79a23b25c8d0
generic

i2c: stub: Reject I2C block transfers with invalid length - kernel/git/stable/linux.git - Linux kernel stable tree

https://git.kernel.org/stable/c/1c4ffe6b4f04365485ed58d64c9bb86b46fc9037
generic

i2c: stub: Reject I2C block transfers with invalid length - kernel/git/stable/linux.git - Linux kernel stable tree

https://git.kernel.org/stable/c/0526931b16e5a118d367b7bfce7d797e63f7ac69

Vendor Advisories for CVE-2026-64191(2)

These vendors published their own advisory mentioning this CVE — often with vendor-specific remediation steps + affected product lists not in NVD.

Data Freshness Timeline

(refreshed 237× in last 7d / 237× in last 30d)

Each row is a source pipeline that fetched or updated this CVE on that date, with what changed. For example, "NVD update" means NVD published or revised its analysis for this CVE; "MITRE cvelistV5" means we ingested or refreshed it from the CNA feed. Most recent first.

Showing the most recent 100 of 237 total refreshes for this CVE.

  1. 2026-07-27 05:21 UTCEG score recompute▲ 7.80
  2. 2026-07-27 05:20 UTCGHSA enrichment
  3. 2026-07-27 05:12 UTCMITRE cvelistV5CVSS v3 → 7.8 · severity → HIGH
  4. 2026-07-26 14:54 UTCEPSS rescore
  5. 2026-07-26 14:54 UTCEPSS rescore
  6. 2026-07-26 10:47 UTCEG score recompute
  7. 2026-07-26 10:47 UTCGHSA enrichment
  8. 2026-07-25 14:18 UTCEPSS rescore
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  14. 2026-07-23 03:22 UTCEG score recompute
  15. 2026-07-22 23:36 UTCEG score recompute
  16. 2026-07-22 23:35 UTCGHSA enrichment
  17. 2026-07-22 14:08 UTCEPSS rescore
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  21. 2026-07-20 23:50 UTCGHSA enrichment
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Frequently asked(5)

What is CVE-2026-64191?
CVE-2026-64191 is a high vulnerability published on July 20, 2026. In the Linux kernel, the following vulnerability has been resolved: i2c: stub: Reject I2C block transfers with invalid length The I2CSMBUSI2CBLOCKDATA case in stub_xfer() uses data->block[0] as the transfer length. The existing check only clamps it to avoid overrunning the chip->words[256] register…
When was CVE-2026-64191 disclosed?
CVE-2026-64191 was first published in the National Vulnerability Database on July 20, 2026, with the most recent update on July 27, 2026. EchelonGraph re-ingests CVE updates from NVD on a 2-hour cycle, so this page reflects the latest published state.
Is CVE-2026-64191 actively exploited?
CVE-2026-64191 is not currently on CISA's Known Exploited Vulnerabilities catalog. FIRST EPSS estimates a 0% probability of exploitation in the next 30 days, which ranks it in the top 92.8% of all scored CVEs.
What is the CVSS score of CVE-2026-64191?
CVE-2026-64191 has a CVSS v3 base score of 7.8 (NVD).
How do I remediate CVE-2026-64191?
Patch to the fixed version published by the affected vendor. Where vendor advisories exist for CVE-2026-64191, EchelonGraph cross-links them in the Vendor Advisories panel below — those typically contain the canonical remediation steps, fixed version numbers, and any vendor-specific mitigations.

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