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Linux KernelOperating system · Linux

CVE-2021-47297

MEDIUM · 5.5 CVSS v3.1 Published 2024-05-21
Fix available
A fix is available. Upgrade to 4.4.277 / 4.9.277 or later.
See remediation →
57/100
Remediation priority · Elevated
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: fix uninit-value in caif_seqpkt_sendmsg When nr_segs equal to zero in iovec_from_user, the object msg->msg_iter.iov is uninit stack memory in caif_seqpkt_sendmsg which is defined in ___sys_sendmsg. So we cann't just judge msg->msg_iter.iov->base directlly. We can use nr_segs to judge msg in caif_seqpkt_sendmsg whether has data buffers. ===================================================== BUG: KMSAN: uninit-value in caif_seqpkt_sendmsg+0x693/0xf60 net/caif/caif_socket.c:542 Call Trace: __dump_stack lib/dump_stack.c:77 [inline] dump_stack+0x1c9/0x220 lib/dump_stack.c:118 kmsan_report+0xf7/0x1e0 mm/kmsan/kmsan_report.c:118 __msan_warning+0x58/0xa0 mm/kmsan/kmsan_instr.c:215 caif_seqpkt_sendmsg+0x693/0xf60 net/caif/caif_socket.c:542 sock_sendmsg_nosec net/socket.c:652 [inline] sock_sendmsg net/socket.c:672 [inline] ____sys_sendmsg+0x12b6/0x1350 net/socket.c:2343 ___sys_sendmsg net/socket.c:2397 [inline] __sys_sendmmsg+0x808/0xc90 net/socket.c:2480 __compat_sys_sendmmsg net/compat.c:656 [inline]

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
How this class of weakness works · CWE-908

Memory or a resource is used before it has been initialised, so its contents are whatever happened to be there — sometimes leaking earlier data, sometimes values an attacker can influence. Behaviour becomes unpredictable and occasionally exploitable. Remediation is initialising every resource before use and ensuring initialisation happens on all code paths.

General guidance for the use of uninitialized resource class — the official description and references above are authoritative for this specific CVE. Want a bespoke review and a reviewed fix? Ask our team →

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:>= 2.6.35, < 4.4.277>= 4.5, < 4.9.277>= 4.10, < 4.14.241>= 4.15, < 4.19.199>= 4.20, < 5.4.136>= 5.5, < 5.10.54>= 5.11, < 5.13.6= 5.14

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
Local
Complexity
Low
Privileges
Low
User interaction
None
Scope
Unchanged
Confidentiality
None
Integrity
None
Availability
High

CVSS:3.1/AV:L/AC:L/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 4.4.277 / 4.9.277 / 4.14.241 or later
Fixed in 4.4.2774.9.2774.14.241
Vendor patch git.kernel.org →
Recommended fix High confidence

4.4.277 / 4.9.277 / 4.14.241 / 4.19.199 (depending on current branch)

  1. 1. Identify the current running kernel version using `uname -r` or `cat /proc/version`
  2. 2. Determine which branch the current kernel belongs to (4.4.x, 4.9.x, 4.14.x, or 4.19.x)
  3. 3. For 4.4.x branch: upgrade to kernel version 4.4.277 or later
  4. 4. For 4.9.x branch: upgrade to kernel version 4.9.277 or later
  5. 5. For 4.14.x branch: upgrade to kernel version 4.14.241 or later
  6. 6. For 4.19.x branch: upgrade to kernel version 4.19.199 or later
  7. 7. Alternatively, apply the upstream commit 1582a02fecffcee306663035a295e28e1c4aaaff to the kernel source and rebuild
  8. 8. Reboot into the patched kernel
Caveat Kernel upgrades may require rebuilding out-of-tree modules and could introduce compatibility issues with older userspace tools

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-2021-47297 in production — separate from our analysis above.

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  • Version or environment caveats, and links to real fixes
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