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Linux KernelOperating system · Linux

CVE-2021-47482

MEDIUM · 5.3 CVSS v3.1 Published 2024-05-22
Fix available
A fix is available. Upgrade to 4.4.293 / 4.9.289 or later.
See remediation →
59/100
Remediation priority · Elevated
Remotely reachable Zero-click Patch available

Official description Straight from the sourceThe vendor's or NVD's own wording, published unedited. Authoritative, but often terse — it says what broke, rarely what to do.

NVD · unedited
In the Linux kernel, the following vulnerability has been resolved: net: batman-adv: fix error handling Syzbot reported ODEBUG warning in batadv_nc_mesh_free(). The problem was in wrong error handling in batadv_mesh_init(). Before this patch batadv_mesh_init() was calling batadv_mesh_free() in case of any batadv_*_init() calls failure. This approach may work well, when there is some kind of indicator, which can tell which parts of batadv are initialized; but there isn't any. All written above lead to cleaning up uninitialized fields. Even if we hide ODEBUG warning by initializing bat_priv->nc.work, syzbot was able to hit GPF in batadv_nc_purge_paths(), because hash pointer in still NULL. [1] To fix these bugs we can unwind batadv_*_init() calls one by one. It is good approach for 2 reasons: 1) It fixes bugs on error handling path 2) It improves the performance, since we won't call unneeded batadv_*_free() functions. So, this patch makes all batadv_*_init() clean up all allocated memory before returning with an error to no call correspoing batadv_*_free() and open-codes batadv_mesh_free() with proper order to avoid touching uninitialized fields.

Technical summary Written by usOur analysis, written from the advisory, the CVSS vector and the affected-version data. It adds context the advisory leaves out, and never invents facts that are not in the source.

dbcve analysis

A detailed technical summary for this CVE is being prepared.

Affected products & versions What the vendor confirmedThe version ranges the vendor confirmed as vulnerable. If your version sits inside a range here, treat yourself as exposed until you have upgraded.

NVD · CPE data
Linux KernelOperating system
Affected:>= 2.6.38, < 4.4.293>= 4.5, < 4.9.289>= 4.10, < 4.14.254>= 4.15, < 4.19.215>= 4.20, < 5.4.157>= 5.5, < 5.10.77>= 5.11, < 5.14.16= 5.15

CVSS breakdown How the score is builtThe industry scoring standard. It rates how the flaw is reached, what it takes to exploit, and what an attacker gains — the score is derived from those, not the other way round.

From the vector
Attack vector
Network
Complexity
High
Privileges
Low
User interaction
None
Scope
Unchanged
Confidentiality
None
Integrity
None
Availability
High

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

Remediation Closing itWhat it takes to close this. Where a vendor fix exists we point at it; where none exists we say so plainly, and can build one. Effort estimates are scoped from the advisory, not from your codebase.

dbcve · scoped
Upgrade available Upgrade to 4.4.293 / 4.9.289 / 4.14.254 or later
Fixed in 4.4.2934.9.2894.14.254
Vendor patch git.kernel.org →
Recommended fix High confidence

Kernel >= 4.4.293, 4.9.289, 4.14.254, or 4.19.215 (depending on your branch)

  1. Identify your current Linux kernel version using 'uname -r'
  2. Determine which kernel branch you are running (e.g., 4.4.x, 4.9.x, 4.14.x, 4.19.x)
  3. Upgrade to a kernel version >= 4.4.293 if running 4.4.x branch
  4. Upgrade to a kernel version >= 4.9.289 if running 4.9.x branch
  5. Upgrade to a kernel version >= 4.14.254 if running 4.14.x branch
  6. Upgrade to a kernel version >= 4.19.215 if running 4.19.x branch
  7. Reboot the system after applying the kernel upgrade
  8. Verify the fix is applied by checking the kernel version matches or exceeds the appropriate fixed version
Caveat Standard kernel upgrade considerations apply - ensure compatibility with hardware drivers and custom modules before rebooting

Generated from the published advisory — verify against the referenced sources before acting.

We can perform the upgrade in your staging environment and verify nothing breaks — typical engagement from $1,600. Get the upgrade done

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References Go to the primary sourcePrimary sources — vendor advisories, patches and trackers. Where our summary and a reference disagree, the reference wins.

Primary sources

Practitioner notes

Contributed

Peer-ranked notes from engineers who’ve handled CVE-2021-47482 in production — separate from our analysis above.

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What this is

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  • Version or environment caveats, and links to real fixes
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