Linux Kernel up to 6.18.51/7.2.5 AMD HSMP hsmp.c hsmp_hwmon_write power1_cap signed conversion

CVSS Meta Temp Score
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CTI Interest Score
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3.3$0-$5k0.00

Summaryinfo

A vulnerability labeled as problematic has been found in Linux Kernel up to 6.18.51/7.2.5. The affected element is the function hsmp_hwmon_write of the file hsmp.c of the component AMD HSMP. Executing a manipulation of the argument power1_cap can lead to signed conversion. The identification of this vulnerability is CVE-2026-90136. The attack can only be executed locally. There is no exploit available. The affected component should be upgraded.

Detailsinfo

A vulnerability was found in Linux Kernel up to 6.18.51/7.2.5. It has been declared as problematic. This vulnerability affects the function hsmp_hwmon_write of the file hsmp.c of the component AMD HSMP. The manipulation of the argument power1_cap with an unknown input leads to a signed conversion vulnerability. The CWE definition for the vulnerability is CWE-195. The product uses a signed primitive and performs a cast to an unsigned primitive, which can produce an unexpected value if the value of the signed primitive can not be represented using an unsigned primitive. As an impact it is known to affect integrity, and availability. CVE summarizes:

In the Linux kernel, the following vulnerability has been resolved: platform/x86/amd/hsmp: Reject negative power cap writes in hwmon hsmp_hwmon_write() takes the user-supplied hwmon value as a signed long and assigns "val / MICROWATT_PER_MILLIWATT" to msg.args[0], which is a __u32. MICROWATT_PER_MILLIWATT is an unsigned long, so a negative write to power1_cap (e.g. "echo -1 > power1_cap") is first converted to a huge unsigned value by the division and then stored into the u32 argument. As a result a nonsensical, multi-gigawatt socket power limit is sent to the SMU via HSMP_SET_SOCKET_POWER_LIMIT instead of the write being rejected. Reject negative values with -EINVAL before the conversion. Tested with HSMP enabled: CAP=$(dirname $(grep -l amd_hsmp_hwmon \ /sys/class/hwmon/hwmon*/name | head -1))/power1_cap # negative write echo -1000000 > $CAP ; echo "ret=$?" # valid positive write must still work echo 400000000 > $CAP ; echo "ret=$?" Before: # echo -1000000 > $CAP ; echo "ret=$?" ret=0 <- accepted; bogus limit sent to SMU # echo 400000000 > $CAP ; echo "ret=$?" ret=0 After: # echo -1000000 > $CAP ; echo "ret=$?" bash: echo: write error: Invalid argument ret=1 <- rejected with -EINVAL # echo 400000000 > $CAP ; echo "ret=$?" ret=0 <- valid write still works

The advisory is available at git.kernel.org. This vulnerability was named CVE-2026-90136 since 09/11/2026. The exploitation appears to be easy. Local access is required to approach this attack. Additional levels of successful authentication are needed for exploitation. Technical details are known, but there is no available exploit.

Upgrading to version 6.18.52, 7.2.6 or 7.3-rc1 eliminates this vulnerability. Applying the patch 2c09cadec116eba3fdbcb5d8d8641f6777d4a11f/1b0a3d915320f1600e5ff43f8bc21b73118480b8/3921bb8635ff2836622df1cdf3194d4f3c1835a4 is able to eliminate this problem. The best possible mitigation is suggested to be upgrading to the latest version.

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Productinfo

Type

Vendor

Name

Version

License

Website

CPE 2.3info

CPE 2.2info

CVSSv4info

VulDB Vector: 🔒
VulDB Reliability: 🔍

CVSSv3info

VulDB Meta Base Score: 3.4
VulDB Meta Temp Score: 3.3

VulDB Base Score: 3.4
VulDB Temp Score: 3.3
VulDB Vector: 🔒
VulDB Reliability: 🔍

CVSSv2info

AVACAuCIA
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VectorComplexityAuthenticationConfidentialityIntegrityAvailability
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VulDB Base Score: 🔒
VulDB Temp Score: 🔒
VulDB Reliability: 🔍

Exploitinginfo

Class: Signed conversion
CWE: CWE-195 / CWE-194 / CWE-189
CAPEC: 🔒
ATT&CK: 🔒

Physical: Partially
Local: Yes
Remote: No

Availability: 🔒
Status: Not defined
Price Prediction: 🔍
Current Price Estimation: 🔒

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Threat Intelligenceinfo

Interest: 🔍
Active Actors: 🔍
Active APT Groups: 🔍

Countermeasuresinfo

Recommended: Upgrade
Status: 🔍

0-Day Time: 🔒

Upgrade: Kernel 6.18.52/7.2.6/7.3-rc1
Patch: 2c09cadec116eba3fdbcb5d8d8641f6777d4a11f/1b0a3d915320f1600e5ff43f8bc21b73118480b8/3921bb8635ff2836622df1cdf3194d4f3c1835a4

Timelineinfo

09/11/2026 CVE reserved
09/17/2026 +6 days Advisory disclosed
09/17/2026 +0 days VulDB entry created
09/17/2026 +0 days VulDB entry last update

Sourcesinfo

Vendor: kernel.org

Advisory: git.kernel.org
Status: Confirmed

CVE: CVE-2026-90136 (🔒)
GCVE (CVE): GCVE-0-2026-90136
GCVE (VulDB): GCVE-100-406654

Entryinfo

Created: 09/17/2026 19:52
Changes: 09/17/2026 19:52 (61)
Complete: 🔍
Cache ID: 216::103

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