CVE-2021-47587: Linux Kernel vulnerability (CVSS 9.8)

Description

In the Linux kernel, the following vulnerability has been resolved: net: systemport: Add global locking for descriptor lifecycle The descriptor list is a shared resource across all of the transmit queues, and the locking mechanism used today only protects concurrency across a given transmit queue between the transmit and reclaiming. This creates an opportunity for the SYSTEMPORT hardware to work on corrupted descriptors if we have multiple producers at once which is the case when using multiple transmit queues. This was particularly noticeable when using multiple flows/transmit queues and it showed up in interesting ways in that UDP packets would get a correct UDP header checksum being calculated over an incorrect packet length. Similarly TCP packets would get an equally correct checksum computed by the hardware over an incorrect packet length. The SYSTEMPORT hardware maintains an internal descriptor list that it re-arranges when the driver produces a new descriptor anytime it writes to the WRITE_PORT_{HI,LO} registers, there is however some delay in the hardware to re-organize its descriptors and it is possible that concurrent TX queues eventually break this internal allocation scheme to the point where the length/status part of the descriptor gets used for an incorrect data buffer. The fix is to impose a global serialization for all TX queues in the short section where we are writing to the WRITE_PORT_{HI,LO} registers which solves the corruption even with multiple concurrent TX queues being used.

CVSS 3.1 breakdown

Attack vectorNetwork

Attack complexityLow

Privileges requiredNone

User interactionNone

ScopeUnchanged

ConfidentialityHigh

IntegrityHigh

AvailabilityHigh

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

Affected products

Linux Kernel≥ 3.16 < 4.4.296 · ≥ 4.10 < 4.14.259 · ≥ 4.15 < 4.19.222 · ≥ 4.20 < 5.4.168

Remediation

Fixed in

Linux Kernel≥ 4.4.296

Patch & vendor advisories

References

Related CVEs

Recent high-severity vulnerabilities sharing a weakness type.

Frequently asked

Is CVE-2021-47587 being actively exploited?

CVE-2021-47587 is not in the CISA KEV catalog. Its EPSS exploit probability is 0.55%.

How severe is CVE-2021-47587?

CVE-2021-47587 has a CVSS 3.1 base score of 9.8, rated critical. EPSS estimates a 0.55% probability of exploitation.

Which products are affected by CVE-2021-47587?

Affected products include Linux Kernel.

How do I fix CVE-2021-47587?

Upgrade affected software to a fixed version, for example Linux Kernel 4.4.296 or later, then confirm no affected versions remain in your inventory.

How Secuno handles this

Secuno correlates vulnerabilities like CVE-2021-47587 against the real software inventory on every managed device, every day. Rather than a static severity, each match is scored in context: exploit availability, EPSS, the asset's exposure, and business criticality decide where it lands in the queue. If an affected version is present anywhere across your portfolio, it surfaces automatically with a prioritised remediation path.

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