Description
In the Linux kernel, the following vulnerability has been resolved:
usb: typec: tcpm: bound altmode_desc[] per iteration in svdm_consume_modes()
svdm_consume_modes() checks pmdata->altmodes against the array size once
before the loop over the count, but forgot to check the bound at every
point in the loop.
In the well-behaved SVDM discovery flow this is harmless because each of
at most SVID_DISCOVERY_MAX SVIDs contributes at most MODE_DISCOVERY_MAX
modes, exactly filling altmode_desc[ALTMODE_DISCOVERY_MAX]. But the
CMDT_RSP_ACK handler in tcpm_pd_svdm() does not correlate an incoming
ACK with any request the port actually sent. Once port->partner is set,
an unsolicited Discover Modes ACK is consumed unconditionally. A broken
or malicious port partner can therefore drive altmodes to
ALTMODE_DISCOVERY_MAX - 1 via the normal flow, and then send one extra
Discover Modes ACK with seven VDOs. Because the pre-loop check passes,
the loop could then writes up to five entries past altmode_desc[]. For
mode_data_prime the next field in struct tcpm_port is the
partner_altmode[] pointer array, which then receives partner-chosen
SVID/VDO bytes.
Move the bound check inside the loop so the array can never be indexed
past ALTMODE_DISCOVERY_MAX regardless of how many VDOs the partner
supplies or how the function was reached.
usb: typec: tcpm: bound altmode_desc[] per iteration in svdm_consume_modes()
svdm_consume_modes() checks pmdata->altmodes against the array size once
before the loop over the count, but forgot to check the bound at every
point in the loop.
In the well-behaved SVDM discovery flow this is harmless because each of
at most SVID_DISCOVERY_MAX SVIDs contributes at most MODE_DISCOVERY_MAX
modes, exactly filling altmode_desc[ALTMODE_DISCOVERY_MAX]. But the
CMDT_RSP_ACK handler in tcpm_pd_svdm() does not correlate an incoming
ACK with any request the port actually sent. Once port->partner is set,
an unsolicited Discover Modes ACK is consumed unconditionally. A broken
or malicious port partner can therefore drive altmodes to
ALTMODE_DISCOVERY_MAX - 1 via the normal flow, and then send one extra
Discover Modes ACK with seven VDOs. Because the pre-loop check passes,
the loop could then writes up to five entries past altmode_desc[]. For
mode_data_prime the next field in struct tcpm_port is the
partner_altmode[] pointer array, which then receives partner-chosen
SVID/VDO bytes.
Move the bound check inside the loop so the array can never be indexed
past ALTMODE_DISCOVERY_MAX regardless of how many VDOs the partner
supplies or how the function was reached.
Published:
2026-07-19
Score:
n/a
EPSS:
n/a
KEV:
No
Impact:
n/a
Action:
n/a
Analysis
No analysis available yet.
Default status is the baseline for the product, each version can override it (e.g. patched versions marked unaffected).
| Vendor | Product | Default status | Versions | |||||||||||||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Linux | Linux | unaffected |
|
|||||||||||||||||||||
| Linux | Linux | affected |
|
No data.
No data.
No data available yet.
Remediation
No remediation available yet.
Tracking
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Advisories
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References
History
Sun, 19 Jul 2026 15:30:00 +0000
| Type | Values Removed | Values Added |
|---|---|---|
| Description | In the Linux kernel, the following vulnerability has been resolved: usb: typec: tcpm: bound altmode_desc[] per iteration in svdm_consume_modes() svdm_consume_modes() checks pmdata->altmodes against the array size once before the loop over the count, but forgot to check the bound at every point in the loop. In the well-behaved SVDM discovery flow this is harmless because each of at most SVID_DISCOVERY_MAX SVIDs contributes at most MODE_DISCOVERY_MAX modes, exactly filling altmode_desc[ALTMODE_DISCOVERY_MAX]. But the CMDT_RSP_ACK handler in tcpm_pd_svdm() does not correlate an incoming ACK with any request the port actually sent. Once port->partner is set, an unsolicited Discover Modes ACK is consumed unconditionally. A broken or malicious port partner can therefore drive altmodes to ALTMODE_DISCOVERY_MAX - 1 via the normal flow, and then send one extra Discover Modes ACK with seven VDOs. Because the pre-loop check passes, the loop could then writes up to five entries past altmode_desc[]. For mode_data_prime the next field in struct tcpm_port is the partner_altmode[] pointer array, which then receives partner-chosen SVID/VDO bytes. Move the bound check inside the loop so the array can never be indexed past ALTMODE_DISCOVERY_MAX regardless of how many VDOs the partner supplies or how the function was reached. | |
| Title | usb: typec: tcpm: bound altmode_desc[] per iteration in svdm_consume_modes() | |
| First Time appeared |
Linux
Linux linux Kernel |
|
| CPEs | cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:* | |
| Vendors & Products |
Linux
Linux linux Kernel |
|
| References |
|
MITRE
Status: PUBLISHED
Assigner: Linux
Published:
Updated: 2026-07-20T06:41:42.766Z
Reserved: 2026-07-19T07:54:57.024Z
Link: CVE-2026-63962
Vulnrichment
No data.
NVD
No data.
Redhat
No data.
OpenCVE Enrichment
No data.
Weaknesses
No weakness.