Out-of-Bounds Read in Linux kernel (CVE-2021-47243)
Summary
Vulnerability in Linux kernel (CVE-2021-47243). Confidential information can be exposed externally.
Original description
The description as published by the source.
In the Linux kernel, the following vulnerability has been resolved:
sch_cake: Fix out of bounds when parsing TCP options and header
The TCP option parser in cake qdisc (cake_get_tcpopt and
cake_tcph_may_drop) could read one byte out of bounds. When the length
is 1, the execution flow gets into the loop, reads one byte of the
opcode, and if the opcode is neither TCPOPT_EOL nor TCPOPT_NOP, it reads
one more byte, which exceeds the length of 1.
This fix is inspired by commit 9609dad263f8 ("ipv4: tcp_input: fix stack
out of bounds when parsing TCP options.").
v2 changes:
Added doff validation in cake_get_tcphdr to avoid parsing garbage as TCP
header. Although it wasn't strictly an out-of-bounds access (memory was
allocated), garbage values could be read where CAKE expected the TCP
header if doff was smaller than 5.
Source: NIST National Vulnerability Database NVD
Auto-generated summary
Assembled by SecPulse from the source data (CVSS, CWE, affected versions) using templates — no AI involved. Check the original description and references below for exact details.
A vulnerability tracked as CVE-2021-47243 has been found in Linux kernel.
Confidential information can be exposed externally. CVSS score: 7.1/10.
What to do: apply the vendor's official patched release.
If unsure, ask your IT team or search "Linux kernel CVE-2021-47243" on the vendor's site.
CVE-2021-47243 (Linux kernel) — CWE-125 / CVSS v3 7.1
Attack vector: local / no user interaction
Plan: 1) Audit SBOM/dependencies, 2) Stage→prod upgrade, 3) Add WAF/proxy monitoring on affected endpoints, 4) Hunt IOCs in logs.
Refs: see the GHSA / vendor advisory / patched release linked on this page.
Out-of-bounds read (CWE-125) exists in Linux kernel.
Check the vendor advisory for the affected versions of Linux kernel.
Severity: High (CVSS 7.1/10). Confidential information can be exposed externally.
Update to the patched release per vendor advisory.
Until the patch is applied: disable the affected feature, apply WAF rules, or restrict access via network ACLs.
Search webserver/proxy logs for unusual request patterns matching this CVE's known IOCs. Audit SBOM/dependencies to find affected services.
Response actions
Concrete steps and command examples for SOC/SRE teams to execute in order
-
1Identify exposure identify
Audit SBOM/dependencies for affected components.資産台帳・SBOM・依存マニフェストで Linux kernel を使っているサービスとバージョンを洗い出す。
-
2Post-deployment verification verify
Confirm patched version is live in productionパッチ適用後、ステージングで PoC または同等の悪用パターンを再現して脆弱性が閉じたことを確認。本番ではアクセスログ・WAF でアラート再発が無いか継続監視。
Fix status by distribution
Fixed packages published by each distribution for this CVE
- Debian DEBIAN-CVE-2021-47243 linux Fixed in: 5.10.46-1
- Ubuntu UBUNTU-CVE-2021-47243 linux-hwe-edge
References
- patch git.kernel.org
- patch git.kernel.org
- patch git.kernel.org
- patch git.kernel.org
- patch git.kernel.org