CVE-2021-46939: Software Security Vulnerability Vulnerability

MODERATE
Advisory Identifier: GHSA-8h6j-vxpr-4ff5
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CVSS 5.5
CWE-662 CWE-400
Published
Advisory Summary

CVE-2021-46939 is a MODERATE (CVSS 5.5) security vulnerability vulnerability (CWE-662: Improper Synchronization) affecting Software libraries in the Maven ecosystem. The weakness occurs when the product utilizes multiple threads, processes, components, or systems to allow temporary access to a shared resource that can only be exclusive to one process at a time, but it does not properly synchronize these actions, which might cause simultaneous accesses of this resource by multiple threads or processes.. Remediation is available in the latest vendor maintenance releases.

CVE-2021-46939 at a Glance

CVE Identifier CVE-2021-46939
GHSA Identifier GHSA-8h6j-vxpr-4ff5
Severity MODERATE
CVSS v3.1 Base Score 5.5
CWE Classification CWE-662: Improper Synchronization
Affected Product Software
Package Ecosystem Maven
Published Date
Last Updated

Security Impact

CVSS: 5.5

The security impact metrics below are parsed directly from the CVSS v3.1 vector string (CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H).

Attack Vector Local (AV:L)
Attack Complexity Low (AC:L)
Privileges Required Low (PR:L)
User Interaction None (UI:N)
Scope Unchanged (S:U)
Confidentiality None (C:N)
Integrity None (I:N)
Availability High (A:H)

How to Fix CVE-2021-46939

To remediate this vulnerability, upgrade all affected Software dependencies to a patched release. Both direct and transitive dependencies should be checked, as frameworks or security libraries may pull in vulnerable versions transitively.

Verify Direct and Transitive Dependencies

Run the following command in your project directory to verify that all resolved dependencies use the patched release: 

mvn dependency:tree

How to Check if You Are Affected

To determine whether your Java application is affected by CVE-2021-46939, inspect your build dependencies using the Maven Dependency Plugin:

mvn dependency:tree

Analyze the terminal output to locate any version of Software in your dependency tree. If any resolved version matches the vulnerable ranges listed in the table below (for example, versions earlier than the patched release), your application is affected.

Note: The mvn dependency:tree command inspects the resolved dependency graph declared in your project's POM files; it does not perform automated security scanning or inspect runtime dynamic classpaths. Always verify runtime container classpaths and shaded JARs.

Technical Details

Vulnerability Mechanism & Technical Analysis

This vulnerability is classified under CWE-662: Improper Synchronization, where the product utilizes multiple threads, processes, components, or systems to allow temporary access to a shared resource that can only be exclusive to one process at a time, but it does not properly synchronize these actions, which might cause simultaneous accesses of this resource by multiple threads or processes. In Software, software state validation or input boundaries are circumvented during processing. Review the official source advisory statement below for specific affected components, classes, and reproduction details.

Source Advisory Statement

In the Linux kernel, the following vulnerability has been resolved: tracing: Restructure trace_clock_global() to never block It was reported that a fix to the ring buffer recursion detection would cause a hung machine when performing suspend / resume testing. The following backtrace was extracted from debugging that case: Call Trace: trace_clock_global+0x91/0xa0 __rb_reserve_next+0x237/0x460 ring_buffer_lock_reserve+0x12a/0x3f0 trace_buffer_lock_reserve+0x10/0x50 __trace_graph_return+0x1f/0x80 trace_graph_return+0xb7/0xf0 ? trace_clock_global+0x91/0xa0 ftrace_return_to_handler+0x8b/0xf0 ? pv_hash+0xa0/0xa0 return_to_handler+0x15/0x30 ? ftrace_graph_caller+0xa0/0xa0 ? trace_clock_global+0x91/0xa0 ? __rb_reserve_next+0x237/0x460 ? ring_buffer_lock_reserve+0x12a/0x3f0 ? trace_event_buffer_lock_reserve+0x3c/0x120 ? trace_event_buffer_reserve+0x6b/0xc0 ? trace_event_raw_event_device_pm_callback_start+0x125/0x2d0 ? dpm_run_callback+0x3b/0xc0 ? pm_ops_is_empty+0x50/0x50 ? platform_get_irq_byname_optional+0x90/0x90 ? trace_device_pm_callback_start+0x82/0xd0 ? dpm_run_callback+0x49/0xc0 With the following RIP: RIP: 0010:native_queued_spin_lock_slowpath+0x69/0x200 Since the fix to the recursion detection would allow a single recursion to happen while tracing, this lead to the trace_clock_global() taking a spin lock and then trying to take it again: ring_buffer_lock_reserve() { trace_clock_global() { arch_spin_lock() { queued_spin_lock_slowpath() { /* lock taken */ (something else gets traced by function graph tracer) ring_buffer_lock_reserve() { trace_clock_global() { arch_spin_lock() { queued_spin_lock_slowpath() { /* DEAD LOCK! */ Tracing should *never* block, as it can lead to strange lockups like the above. Restructure the trace_clock_global() code to instead of simply taking a lock to update the recorded "prev_time" simply use it, as two events happening on two different CPUs that calls this at the same time, really doesn't matter which one goes first. Use a trylock to grab the lock for updating the prev_time, and if it fails, simply try again the next time. If it failed to be taken, that means something else is already updating it. Bugzilla: https://bugzilla.kernel.org/show_bug.cgi?id=212761

References

NVD — CVE-2021-46939 NVD
https://nvd.nist.gov/vuln/detail/CVE-2021-46939
git.kernel.org/stable/c/1fca009203... WEB
https://git.kernel.org/stable/c/1fca00920327be96f3318224f502e4d5460f9545
git.kernel.org/stable/c/2a1bd74b81... WEB
https://git.kernel.org/stable/c/2a1bd74b8186d7938bf004f5603f25b84785f63e
git.kernel.org/stable/c/6e24185762... WEB
https://git.kernel.org/stable/c/6e2418576228eeb12e7ba82edb8f9500623942ff
git.kernel.org/stable/c/859b47a43f... WEB
https://git.kernel.org/stable/c/859b47a43f5a0e5b9a92b621dc6ceaad39fb5c8b
git.kernel.org/stable/c/91ca6f6a91... WEB
https://git.kernel.org/stable/c/91ca6f6a91f679c8645d7f3307e03ce86ad518c4
git.kernel.org/stable/c/a33614d52e... WEB
https://git.kernel.org/stable/c/a33614d52e97fc8077eb0b292189ca7d964cc534
git.kernel.org/stable/c/aafe104aa9... WEB
https://git.kernel.org/stable/c/aafe104aa9096827a429bc1358f8260ee565b7cc
git.kernel.org/stable/c/c64da3294a... WEB
https://git.kernel.org/stable/c/c64da3294a7d59a4bf6874c664c13be892f15f44
git.kernel.org/stable/c/d43d56dbf4... WEB
https://git.kernel.org/stable/c/d43d56dbf452ccecc1ec735cd4b6840118005d7c

Frequently Asked Questions

What is CVE-2021-46939?
CVE-2021-46939 is a security vulnerability in Software classified as a security vulnerability vulnerability under CWE-662: Improper Synchronization.
Which Software versions are affected?
Affected versions include releases prior to current release patches.
What version fixes CVE-2021-46939?
Upgrading to current release patches (or the latest patched release for your respective branch) resolves the vulnerability.
What is the CVSS score of CVE-2021-46939?
CVE-2021-46939 has a CVSS v3.1 base score of 5.5 (MODERATE) with vector string CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H.
What CWE is associated with CVE-2021-46939?
CVE-2021-46939 is classified under CWE-662: Improper Synchronization (The product utilizes multiple threads, processes, components, or systems to allow temporary access to a shared resource that can only be exclusive to one process at a time, but it does not properly synchronize these actions, which might cause simultaneous accesses of this resource by multiple threads or processes.).
How can I check Maven dependencies for CVE-2021-46939?
Run the dependency tree command: 'mvn dependency:tree'. This command lists direct and transitive dependencies in your build configuration so you can verify if a vulnerable version is resolved.
Machine-readable OSV JSON OSV v1.5 Schema
Normalized schema output
View Raw JSON 
{
  "schema_version" : "1.4.0",
  "id" : "GHSA-8h6j-vxpr-4ff5",
  "modified" : "2024-04-10T21:30:28Z",
  "published" : "2024-02-27T21:31:26Z",
  "aliases" : [ "CVE-2021-46939" ],
  "details" : "In the Linux kernel, the following vulnerability has been resolved:\n\ntracing: Restructure trace_clock_global() to never block\n\nIt was reported that a fix to the ring buffer recursion detection would\ncause a hung machine when performing suspend / resume testing. The\nfollowing backtrace was extracted from debugging that case:\n\nCall Trace:\n trace_clock_global+0x91/0xa0\n __rb_reserve_next+0x237/0x460\n ring_buffer_lock_reserve+0x12a/0x3f0\n trace_buffer_lock_reserve+0x10/0x50\n __trace_graph_return+0x1f/0x80\n trace_graph_return+0xb7/0xf0\n ? trace_clock_global+0x91/0xa0\n ftrace_return_to_handler+0x8b/0xf0\n ? pv_hash+0xa0/0xa0\n return_to_handler+0x15/0x30\n ? ftrace_graph_caller+0xa0/0xa0\n ? trace_clock_global+0x91/0xa0\n ? __rb_reserve_next+0x237/0x460\n ? ring_buffer_lock_reserve+0x12a/0x3f0\n ? trace_event_buffer_lock_reserve+0x3c/0x120\n ? trace_event_buffer_reserve+0x6b/0xc0\n ? trace_event_raw_event_device_pm_callback_start+0x125/0x2d0\n ? dpm_run_callback+0x3b/0xc0\n ? pm_ops_is_empty+0x50/0x50\n ? platform_get_irq_byname_optional+0x90/0x90\n ? trace_device_pm_callback_start+0x82/0xd0\n ? dpm_run_callback+0x49/0xc0\n\nWith the following RIP:\n\nRIP: 0010:native_queued_spin_lock_slowpath+0x69/0x200\n\nSince the fix to the recursion detection would allow a single recursion to\nhappen while tracing, this lead to the trace_clock_global() taking a spin\nlock and then trying to take it again:\n\nring_buffer_lock_reserve() {\n  trace_clock_global() {\n    arch_spin_lock() {\n      queued_spin_lock_slowpath() {\n        /* lock taken */\n        (something else gets traced by function graph tracer)\n          ring_buffer_lock_reserve() {\n            trace_clock_global() {\n              arch_spin_lock() {\n                queued_spin_lock_slowpath() {\n                /* DEAD LOCK! */\n\nTracing should *never* block, as it can lead to strange lockups like the\nabove.\n\nRestructure the trace_clock_global() code to instead of simply taking a\nlock to update the recorded \"prev_time\" simply use it, as two events\nhappening on two different CPUs that calls this at the same time, really\ndoesn't matter which one goes first. Use a trylock to grab the lock for\nupdating the prev_time, and if it fails, simply try again the next time.\nIf it failed to be taken, that means something else is already updating\nit.\n\n\nBugzilla: https://bugzilla.kernel.org/show_bug.cgi?id=212761",
  "severity" : [ {
    "type" : "CVSS_V3",
    "score" : "CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H"
  } ],
  "affected" : [ ],
  "references" : [ {
    "type" : "ADVISORY",
    "url" : "https://nvd.nist.gov/vuln/detail/CVE-2021-46939"
  }, {
    "type" : "WEB",
    "url" : "https://git.kernel.org/stable/c/1fca00920327be96f3318224f502e4d5460f9545"
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    "type" : "WEB",
    "url" : "https://git.kernel.org/stable/c/2a1bd74b8186d7938bf004f5603f25b84785f63e"
  }, {
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    "url" : "https://git.kernel.org/stable/c/6e2418576228eeb12e7ba82edb8f9500623942ff"
  }, {
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    "url" : "https://git.kernel.org/stable/c/859b47a43f5a0e5b9a92b621dc6ceaad39fb5c8b"
  }, {
    "type" : "WEB",
    "url" : "https://git.kernel.org/stable/c/91ca6f6a91f679c8645d7f3307e03ce86ad518c4"
  }, {
    "type" : "WEB",
    "url" : "https://git.kernel.org/stable/c/a33614d52e97fc8077eb0b292189ca7d964cc534"
  }, {
    "type" : "WEB",
    "url" : "https://git.kernel.org/stable/c/aafe104aa9096827a429bc1358f8260ee565b7cc"
  }, {
    "type" : "WEB",
    "url" : "https://git.kernel.org/stable/c/c64da3294a7d59a4bf6874c664c13be892f15f44"
  }, {
    "type" : "WEB",
    "url" : "https://git.kernel.org/stable/c/d43d56dbf452ccecc1ec735cd4b6840118005d7c"
  } ],
  "database_specific" : {
    "cwe_ids" : [ "CWE-400", "CWE-662" ],
    "severity" : "MODERATE",
    "github_reviewed" : false,
    "github_reviewed_at" : null,
    "nvd_published_at" : "2024-02-27T19:04:05Z"
  }
}