CyberSecBulletin
CVE-2021-29256Exploited in the wildNVD status: Analyzed

Arm Mali GPU Kernel Driver Use-After-Free

Published Updated By the CyberSecBulletin desk

CVE-2021-29256 is a high-severity use after free vulnerability in Bifrost GPU Kernel Driver from Arm, with a CVSS 3.1 base score of 8.8 out of 10. It can be exploited remotely over the network by an attacker with a low-privileged account, without any action from a user. The record lists version r30p0 as the first without the flaw, so updating Bifrost GPU Kernel Driver to that release or later removes the exposure. CISA added it to the Known Exploited Vulnerabilities catalogue on July 7, 2023, which means attacks have been observed in the wild.

Patch now

Attackers are already exploiting this vulnerability, according to CISA.

What to do

  1. Update Bifrost GPU Kernel Driver to r30p0 or a later version.
  2. Update Midgard GPU Kernel Driver to r31p0 or a later version.
  3. Update Valhall GPU Kernel Driver to r30p0 or a later version.
  4. CISA's required action: Apply updates per vendor instructions or discontinue use of the product if updates are unavailable.
  5. Read the advisory on developer.arm.com for workarounds and exact fixed builds.

Affected products and versions

VendorProductAffected versionsFixed in
ArmBifrost GPU Kernel Driverr16p0 up to, but not including, r30p0r30p0
ArmMidgard GPU Kernel Driverr28p0 up to, but not including, r31p0r31p0
ArmValhall GPU Kernel Driverr19p0 up to, but not including, r30p0r30p0

Version data comes from NVD's product matching. Confirm against the vendor advisory before deciding you are unaffected.

How the severity score breaks down

Attack vector
NetworkCan be exploited remotely over a network, including the internet.
Attack complexity
LowNo special conditions are needed; the attack works reliably.
Privileges required
LowA basic user account is enough.
User interaction
NoneNo action by a victim is required.
Scope
UnchangedImpact stays within the vulnerable component.
Confidentiality
HighAll data handled by the component can be read.
Integrity
HighData or code can be modified at will.
Availability
HighThe component can be taken down completely.

Vector: CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H. Scored by NVD.

Scoring systemScoreSeverityScored by
CVSS 3.18.8HighNVD
CVSS 3.18.8HighCISA (ADP)
CVSS 2.09.0HighNVD

Official description

. The Arm Mali GPU kernel driver allows an unprivileged user to achieve access to freed memory, leading to information disclosure or root privilege escalation. This affects Bifrost r16p0 through r29p0 before r30p0, Valhall r19p0 through r29p0 before r30p0, and Midgard r28p0 through r30p0.

Source: the CVE record as published by its numbering authority, via NVD and CVE.org.

The underlying weakness: Use After Free

The product reuses or references memory after it has been freed. At some point afterward, the memory may be allocated again and saved in another pointer, while the original pointer references a location somewhere within the new allocation. Any operations using the original pointer are no longer valid because the memory belongs to the code that operates on the new pointer.

How developers prevent this class of flaw

  • Choose a language that provides automatic memory management.
  • When freeing pointers, be sure to set them to NULL once they are freed. However, the utilization of multiple or complex data structures may lower the usefulness of this strategy.

More Use After Free vulnerabilities (CWE-416)

Timeline

  1. CVE record published.
  2. Added to CISA's Known Exploited Vulnerabilities catalogue.
  3. Deadline for US federal agencies to remediate, set by CISA.
  4. CISA published its SSVC assessment (exploitation: active, automatable: no, technical impact: total).
  5. Record last changed materially (score, affected products, status or references).

References

Third-party and government advisories

Other vulnerabilities in Bifrost GPU Kernel Driver

All Bifrost GPU Kernel Driver vulnerabilities

Recent Use After Free vulnerabilities

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