UBUNTU-CVE-2021-47353: Null Pointer Dereference

Q: What conditions are required to trigger the issue?

An attacker or local user needs low-privileged local access and must cause the UDF filesystem symlink path to reach a failure of sb_getblk, which can make udf_tgetblk return NULL. The vulnerable udf_symlink code then uses that NULL buffer-head pointer without checking it.

Q: What is the practical impact if exploitation succeeds?

The reported impact is a denial of service through a NULL pointer dereference, affecting system availability. The provided severity vector indicates no direct impact to confidentiality or integrity.

Q: Which Ubuntu kernel packages are listed as affected?

The listed software includes Ubuntu linux, linux-aws, linux-azure, linux-gcp, and their applicable FIPS variants: linux-aws-fips, linux-azure-fips, and linux-gcp-fips.

Q: What mitigation is indicated by the fix?

The fix validates epos.bh after udf_tgetblk returns, before the pointer is used. No alternative workaround or configuration-based mitigation is provided in the available data.

Published May 21, 2024

Updated

In the Linux kernel, the following vulnerability has been resolved: udf: Fix NULL pointer dereference in udfsymlink function In function udfsymlink, epos.bh is assigned with the value returned by udftgetblk. The function udftgetblk is defined in udf/misc.c and returns the value of sbgetblk function that could be NULL. Then, epos.bh is used without any check, causing a possible NULL pointer dereference when sbgetblk fails. This fix adds a check to validate the value of epos.bh.

Affected Software

118 affected componentsFixes available

ubuntu/linux-azure<4.15.0-1123.136~14.04.1

4.15.0-1123.136~14.04.1

ubuntu/linux*

ubuntu/linux-aws<4.4.0-1144.150

4.4.0-1144.150

ubuntu/linux-lts-xenial<4.4.0-269.303~14.04.1

4.4.0-269.303~14.04.1

ubuntu/linux<4.4.0-269.303

4.4.0-269.303

ubuntu/linux-aws<4.4.0-1182.197

4.4.0-1182.197

ubuntu/linux-aws-hwe<4.15.0-1111.118~16.04.1

4.15.0-1111.118~16.04.1

ubuntu/linux-azure<4.15.0-1123.136~16.04.1

4.15.0-1123.136~16.04.1

ubuntu/linux-gcp<4.15.0-1108.122~16.04.1

4.15.0-1108.122~16.04.1

ubuntu/linux-hwe<4.15.0-156.163~16.04.1

4.15.0-156.163~16.04.1

ubuntu/linux-kvm<4.4.0-1145.156

4.4.0-1145.156

ubuntu/linux-oracle<4.15.0-1080.88~16.04.1

4.15.0-1080.88~16.04.1

ubuntu/linux-hwe-edge*

ubuntu/linux-fips<4.4.0-1114.121

4.4.0-1114.121

ubuntu/linux-fips*

ubuntu/linux<4.15.0-156.163

4.15.0-156.163

ubuntu/linux-aws<4.15.0-1111.118

4.15.0-1111.118

ubuntu/linux-aws-5.4<5.4.0-1056.59~18.04.1

5.4.0-1056.59~18.04.1

ubuntu/linux-azure-4.15<4.15.0-1123.136

4.15.0-1123.136

ubuntu/linux-azure-5.4<5.4.0-1058.60~18.04.1

5.4.0-1058.60~18.04.1

ubuntu/linux-gcp-4.15<4.15.0-1108.122

4.15.0-1108.122

ubuntu/linux-gcp-5.4<5.4.0-1052.56~18.04.1

5.4.0-1052.56~18.04.1

ubuntu/linux-hwe-5.4<5.4.0-84.94~18.04.1

5.4.0-84.94~18.04.1

ubuntu/linux-kvm<4.15.0-1099.101

4.15.0-1099.101

ubuntu/linux-oracle<4.15.0-1080.88

4.15.0-1080.88

ubuntu/linux-oracle-5.4<5.4.0-1054.58~18.04.1

5.4.0-1054.58~18.04.1

ubuntu/linux-raspi-5.4<5.4.0-1043.47~18.04.1

5.4.0-1043.47~18.04.1

ubuntu/linux-aws-5.0*

ubuntu/linux-aws-5.3*

ubuntu/linux-azure*

ubuntu/linux-azure-5.3*

ubuntu/linux-azure-edge*

ubuntu/linux-gcp*

ubuntu/linux-gcp-5.3*

ubuntu/linux-gke-4.15*

ubuntu/linux-gke-5.4*

ubuntu/linux-gkeop-5.4*

ubuntu/linux-hwe*

ubuntu/linux-hwe-edge*

ubuntu/linux-oem*

ubuntu/linux-oracle-5.0*

ubuntu/linux-oracle-5.3*

ubuntu/linux-aws-fips<4.15.0-2053.55

4.15.0-2053.55

ubuntu/linux-azure-fips<4.15.0-2035.39

4.15.0-2035.39

ubuntu/linux-fips<4.15.0-1069.78

4.15.0-1069.78

ubuntu/linux-gcp-fips<4.15.0-2018.20

4.15.0-2018.20

ubuntu/linux-aws-fips*

ubuntu/linux-azure-fips*

ubuntu/linux-fips*

ubuntu/linux-gcp-fips*

ubuntu/linux<5.4.0-84.94

5.4.0-84.94

ubuntu/linux-aws<5.4.0-1056.59

5.4.0-1056.59

ubuntu/linux-azure<5.4.0-1058.60

5.4.0-1058.60

ubuntu/linux-bluefield<5.4.0-1019.22

5.4.0-1019.22

ubuntu/linux-gcp<5.4.0-1052.56

5.4.0-1052.56

ubuntu/linux-gkeop<5.4.0-1023.24

5.4.0-1023.24

ubuntu/linux-kvm<5.4.0-1046.48

5.4.0-1046.48

ubuntu/linux-oracle<5.4.0-1054.58

5.4.0-1054.58

ubuntu/linux-raspi<5.4.0-1043.47

5.4.0-1043.47

ubuntu/linux-aws-5.11*

ubuntu/linux-aws-5.13*

ubuntu/linux-aws-5.8*

ubuntu/linux-azure-5.11*

ubuntu/linux-azure-5.13*

ubuntu/linux-azure-5.8*

ubuntu/linux-azure-fde*

ubuntu/linux-gcp-5.11*

ubuntu/linux-gcp-5.13*

ubuntu/linux-gcp-5.8*

ubuntu/linux-gke*

ubuntu/linux-gke-5.15*

ubuntu/linux-hwe-5.11*

ubuntu/linux-hwe-5.13*

ubuntu/linux-hwe-5.8*

ubuntu/linux-intel-5.13*

ubuntu/linux-oem-5.10*

ubuntu/linux-oem-5.13*

ubuntu/linux-oem-5.6*

ubuntu/linux-oracle-5.11*

ubuntu/linux-oracle-5.13*

ubuntu/linux-oracle-5.8*

ubuntu/linux-raspi2*

ubuntu/linux-riscv*

ubuntu/linux-riscv-5.11*

ubuntu/linux-riscv-5.8*

ubuntu/linux-aws-fips<5.4.0-1069.73+fips2

5.4.0-1069.73+fips2

ubuntu/linux-azure-fips<5.4.0-1073.76+fips1

5.4.0-1073.76+fips1

ubuntu/linux-fips<5.4.0-1033.38

5.4.0-1033.38

ubuntu/linux-gcp-fips<5.4.0-1067.71~20.04.1

5.4.0-1067.71~20.04.1

ubuntu/linux-aws-fips*

ubuntu/linux-azure-fips*

ubuntu/linux-fips*

ubuntu/linux-gcp-fips*

ubuntu/linux-allwinner-5.19*

ubuntu/linux-aws-5.19*

ubuntu/linux-aws-6.2*

ubuntu/linux-azure-5.19*

ubuntu/linux-azure-6.2*

ubuntu/linux-azure-fde-5.19*

ubuntu/linux-azure-fde-6.2*

ubuntu/linux-gcp-5.19*

ubuntu/linux-gcp-6.2*

ubuntu/linux-hwe-5.19*

ubuntu/linux-hwe-6.2*

ubuntu/linux-intel-iot-realtime*

ubuntu/linux-lowlatency-hwe-5.19*

ubuntu/linux-lowlatency-hwe-6.2*

ubuntu/linux-nvidia-6.2*

ubuntu/linux-oem-5.17*

ubuntu/linux-oem-6.0*

ubuntu/linux-oem-6.1*

ubuntu/linux-realtime*

ubuntu/linux-riscv*

ubuntu/linux-riscv-5.19*

ubuntu/linux-starfive-5.19*

ubuntu/linux-starfive-6.2*

ubuntu/linux-raspi-realtime*

ubuntu/linux-vmware*

Remediation

Recommended actions to resolve this vulnerability, in priority order.

Upgrade
Upgrade ubuntu/linux-azure to a version that resolves this vulnerability.
Fixed in 4.15.0-1123.136~14.04.1
Upgrade
Upgrade ubuntu/linux-aws to a version that resolves this vulnerability.
Fixed in 4.4.0-1144.150
Upgrade
Upgrade ubuntu/linux-lts-xenial to a version that resolves this vulnerability.
Fixed in 4.4.0-269.303~14.04.1
Upgrade
Upgrade ubuntu/linux to a version that resolves this vulnerability.
Fixed in 4.4.0-269.303
Upgrade
Upgrade ubuntu/linux-aws to a version that resolves this vulnerability.
Fixed in 4.4.0-1182.197
Upgrade
Upgrade ubuntu/linux-aws-hwe to a version that resolves this vulnerability.
Fixed in 4.15.0-1111.118~16.04.1
Upgrade
Upgrade ubuntu/linux-azure to a version that resolves this vulnerability.
Fixed in 4.15.0-1123.136~16.04.1
Upgrade
Upgrade ubuntu/linux-gcp to a version that resolves this vulnerability.
Fixed in 4.15.0-1108.122~16.04.1
Upgrade
Upgrade ubuntu/linux-hwe to a version that resolves this vulnerability.
Fixed in 4.15.0-156.163~16.04.1
Upgrade
Upgrade ubuntu/linux-kvm to a version that resolves this vulnerability.
Fixed in 4.4.0-1145.156
Upgrade
Upgrade ubuntu/linux-oracle to a version that resolves this vulnerability.
Fixed in 4.15.0-1080.88~16.04.1
Upgrade
Upgrade ubuntu/linux-fips to a version that resolves this vulnerability.
Fixed in 4.4.0-1114.121
Upgrade
Upgrade ubuntu/linux to a version that resolves this vulnerability.
Fixed in 4.15.0-156.163
Upgrade
Upgrade ubuntu/linux-aws to a version that resolves this vulnerability.
Fixed in 4.15.0-1111.118
Upgrade
Upgrade ubuntu/linux-aws-5.4 to a version that resolves this vulnerability.
Fixed in 5.4.0-1056.59~18.04.1
Upgrade
Upgrade ubuntu/linux-azure-4.15 to a version that resolves this vulnerability.
Fixed in 4.15.0-1123.136
Upgrade
Upgrade ubuntu/linux-azure-5.4 to a version that resolves this vulnerability.
Fixed in 5.4.0-1058.60~18.04.1
Upgrade
Upgrade ubuntu/linux-gcp-4.15 to a version that resolves this vulnerability.
Fixed in 4.15.0-1108.122
Upgrade
Upgrade ubuntu/linux-gcp-5.4 to a version that resolves this vulnerability.
Fixed in 5.4.0-1052.56~18.04.1
Upgrade
Upgrade ubuntu/linux-hwe-5.4 to a version that resolves this vulnerability.
Fixed in 5.4.0-84.94~18.04.1
Upgrade
Upgrade ubuntu/linux-kvm to a version that resolves this vulnerability.
Fixed in 4.15.0-1099.101
Upgrade
Upgrade ubuntu/linux-oracle to a version that resolves this vulnerability.
Fixed in 4.15.0-1080.88
Upgrade
Upgrade ubuntu/linux-oracle-5.4 to a version that resolves this vulnerability.
Fixed in 5.4.0-1054.58~18.04.1
Upgrade
Upgrade ubuntu/linux-raspi-5.4 to a version that resolves this vulnerability.
Fixed in 5.4.0-1043.47~18.04.1
Upgrade
Upgrade ubuntu/linux-aws-fips to a version that resolves this vulnerability.
Fixed in 4.15.0-2053.55
Upgrade
Upgrade ubuntu/linux-azure-fips to a version that resolves this vulnerability.
Fixed in 4.15.0-2035.39
Upgrade
Upgrade ubuntu/linux-fips to a version that resolves this vulnerability.
Fixed in 4.15.0-1069.78
Upgrade
Upgrade ubuntu/linux-gcp-fips to a version that resolves this vulnerability.
Fixed in 4.15.0-2018.20
Upgrade
Upgrade ubuntu/linux to a version that resolves this vulnerability.
Fixed in 5.4.0-84.94
Upgrade
Upgrade ubuntu/linux-aws to a version that resolves this vulnerability.
Fixed in 5.4.0-1056.59
Upgrade
Upgrade ubuntu/linux-azure to a version that resolves this vulnerability.
Fixed in 5.4.0-1058.60
Upgrade
Upgrade ubuntu/linux-bluefield to a version that resolves this vulnerability.
Fixed in 5.4.0-1019.22
Upgrade
Upgrade ubuntu/linux-gcp to a version that resolves this vulnerability.
Fixed in 5.4.0-1052.56
Upgrade
Upgrade ubuntu/linux-gkeop to a version that resolves this vulnerability.
Fixed in 5.4.0-1023.24
Upgrade
Upgrade ubuntu/linux-kvm to a version that resolves this vulnerability.
Fixed in 5.4.0-1046.48
Upgrade
Upgrade ubuntu/linux-oracle to a version that resolves this vulnerability.
Fixed in 5.4.0-1054.58
Upgrade
Upgrade ubuntu/linux-raspi to a version that resolves this vulnerability.
Fixed in 5.4.0-1043.47
Upgrade
Upgrade ubuntu/linux-aws-fips to a version that resolves this vulnerability.
Fixed in 5.4.0-1069.73+fips2
Upgrade
Upgrade ubuntu/linux-azure-fips to a version that resolves this vulnerability.
Fixed in 5.4.0-1073.76+fips1
Upgrade
Upgrade ubuntu/linux-fips to a version that resolves this vulnerability.
Fixed in 5.4.0-1033.38
Upgrade
Upgrade ubuntu/linux-gcp-fips to a version that resolves this vulnerability.
Fixed in 5.4.0-1067.71~20.04.1

Event History

May 21, 2024

CVE Published

via OSV·03:15 PM

Data Sourced

via OSV·03:15 PM

DescriptionSeverityAffected Software

Frequently Asked Questions

What conditions are required to trigger the issue?

An attacker or local user needs low-privileged local access and must cause the UDF filesystem symlink path to reach a failure of sb_getblk, which can make udf_tgetblk return NULL. The vulnerable udf_symlink code then uses that NULL buffer-head pointer without checking it.

What is the practical impact if exploitation succeeds?

The reported impact is a denial of service through a NULL pointer dereference, affecting system availability. The provided severity vector indicates no direct impact to confidentiality or integrity.

Which Ubuntu kernel packages are listed as affected?

The listed software includes Ubuntu linux, linux-aws, linux-azure, linux-gcp, and their applicable FIPS variants: linux-aws-fips, linux-azure-fips, and linux-gcp-fips.

What mitigation is indicated by the fix?

The fix validates epos.bh after udf_tgetblk returns, before the pointer is used. No alternative workaround or configuration-based mitigation is provided in the available data.

UBUNTU-CVE-2021-47353: Null Pointer Dereference

Affected Software

Remediation

Event History

Frequently Asked Questions

What conditions are required to trigger the issue?

What is the practical impact if exploitation succeeds?

Which Ubuntu kernel packages are listed as affected?

What mitigation is indicated by the fix?

Company

Resources

Contact

Frequently Asked Questions

What conditions are required to trigger the issue?

What is the practical impact if exploitation succeeds?

Which Ubuntu kernel packages are listed as affected?

What mitigation is indicated by the fix?