CyberSecBulletin
CVE-2016-5195Exploited in the wildNVD status: Analyzed

Linux Kernel Race Condition

Published Updated By the CyberSecBulletin desk

CVE-2016-5195 is a high-severity concurrent execution using shared resource with improper synchronization vulnerability in Ubuntu Linux from Canonical, with a CVSS 3.1 base score of 7.0 out of 10. It can be exploited with local access to the system by an attacker with a low-privileged account, without any action from a user. Affected Ubuntu Linux versions: 12.04; 14.04; 16.04, and others listed below. The record does not name a fixed version, so check the vendor advisory. CISA added it to the Known Exploited Vulnerabilities catalogue on March 3, 2022, 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 Linux Kernel to 3.2.83 or 3.4.113 or 3.10.104 or 3.12.66, whichever matches your release line, or a later version.
  2. Update Pan-os to 7.0.14 or 7.1.8, whichever matches your release line, or a later version.
  3. CISA's required action: Apply updates per vendor instructions.
  4. Read the advisory on git.kernel.org for workarounds and exact fixed builds.

Affected products and versions

VendorProductAffected versionsFixed in
CanonicalUbuntu Linux12.04; 14.04; 16.04; 16.10Not stated
LinuxLinux Kernel2.6.22 up to, but not including, 3.2.83; 3.3 up to, but not including, 3.4.113; 3.5 up to, but not including, 3.10.104; 3.11 up to, but not including, 3.12.66; 3.13 up to, but not including, 3.16.38; 3.17 up to, but not including, 3.18.44; 3.19 up to, but not including, 4.1.35; 4.2 up to, but not including, 4.4.26; and 2 more ranges3.2.83, 3.4.113, 3.10.104, 3.12.66, 3.16.38, 3.18.44
Red HatEnterprise Linux5; 6.0; 7.0Not stated
Red HatEnterprise Linux AUS6.2; 6.4; 6.5Not stated
Red HatEnterprise Linux EUS6.6; 6.7; 7.1Not stated
Red HatEnterprise Linux Long Life5.6; 5.9Not stated
Red HatEnterprise Linux TUS6.5Not stated
DebianDebian Linux7.0; 8.0Not stated
Fedora ProjectFedora23; 24; 25Not stated
Palo Alto NetworksPan-os5.1 up to, but not including, 7.0.14; 7.1.0 up to, but not including, 7.1.87.0.14, 7.1.8
NetAppCloud BackupNot specified in the recordNot stated
NetAppHci Storage NodesNot specified in the recordNot stated
NetAppOncommand BalanceNot specified in the recordNot stated
NetAppOncommand Performance ManagerNot specified in the recordNot stated
NetAppOncommand Unified Manager For Clustered Data OntapNot specified in the recordNot stated
NetAppOntap Select Deploy Administration UtilityNot specified in the recordNot stated
NetAppSnapprotectNot specified in the recordNot stated
NetAppSolidfireNot specified in the recordNot stated

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
LocalThe attacker needs local access or must trick a user into running something.
Attack complexity
HighSuccess depends on conditions outside the attacker's control.
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:L/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:H. Scored by NVD.

Scoring systemScoreSeverityScored by
CVSS 3.17.0HighNVD
CVSS 3.17.0HighCISA (ADP)
CVSS 2.07.2HighNVD

Official description

Race condition in mm/gup.c in the Linux kernel 2.x through 4.x before 4.8.3 allows local users to gain privileges by leveraging incorrect handling of a copy-on-write (COW) feature to write to a read-only memory mapping, as exploited in the wild in October 2016, aka "Dirty COW."

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

The underlying weakness: Concurrent Execution using Shared Resource with Improper Synchronization

The product contains a concurrent code sequence that requires temporary, exclusive access to a shared resource, but a timing window exists in which the shared resource can be modified by another code sequence operating concurrently.

How developers prevent this class of flaw

  • In languages that support it, use synchronization primitives. Only wrap these around critical code to minimize the impact on performance.
  • Use thread-safe capabilities such as the data access abstraction in Spring.
  • Minimize the usage of shared resources in order to remove as much complexity as possible from the control flow and to reduce the likelihood of unexpected conditions occurring. Additionally, this will minimize the amount of synchronization necessary and may even help to reduce the likelihood of a denial of service where an attacker may be able to repeatedly trigger a critical section (CWE-400).

More Concurrent Execution using Shared Resource with Improper Synchronization vulnerabilities (CWE-362)

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

Patches and release notes

Third-party and government advisories

Other references

Other vulnerabilities in Ubuntu Linux

All Ubuntu Linux vulnerabilities

Recent Concurrent Execution using Shared Resource with Improper Synchronization vulnerabilities

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