CVE-2021-47243

HIGHNVD 7.17.1—
EchelonGraph scoreMEDIUM confidence

Score 7.1 from GitHub Security Advisory (severity: HIGH) published 2024-05-21. NVD baseline CVSS 7.1; sources differ by 0.0.

Triggered by: GitHub Security Advisory CVSS
Sources: epss, ghsa, nvd
Trending — 3 sources updated this week
7.1EG
EchelonGraph verdictPlan a fixSerious severity, but no confirmed exploitation yet.
  • High severity, but no confirmed exploitation yet
CISA-KEV: Not listedEPSS PROB: 0%CVSS: 7.1Exploit: None knownExposed: 0

No vendor fix yet — apply a workaround or compensating control (WAF / firewall / segmentation) and watch for a patch.

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.

CVSS v3
7.1
EG Score
7.1(medium)
EG Risk
32(Track)
EG Risk 32/100SSVC: Track

EG Risk is EchelonGraph's 0–100 priority score: it fuses intrinsic severity with real-world exploitation and automatability so you can rank equal-severity CVEs and fix the most dangerous first. Higher = act sooner. Distinct from the 0–10 EG Score (severity).

How it’s computed
Severity71% × 45%
Exploitation0% × 40%
Automatability0% × 15%
Action: Routine — remediate on your standard cadence.
EPSS PROB
0%
EPSS %ILE
17%
KEV
Not listed

Published

May 21, 2024

Last Modified

August 5, 2026

Advisory Details (5)

Auto-updated Aug 5, 2026
No patch confirmed yet.
generic

sch_cake: Fix out of bounds when parsing TCP options and header - kernel/git/stable/linux.git - Linux kernel stable tree

https://git.kernel.org/stable/c/ba91c49dedbde758ba0b72f57ac90b06ddf8e548
generic

sch_cake: Fix out of bounds when parsing TCP options and header - kernel/git/stable/linux.git - Linux kernel stable tree

https://git.kernel.org/stable/c/3371392c60e2685af30bd4547badd880f5df2b3f
generic

sch_cake: Fix out of bounds when parsing TCP options and header - kernel/git/stable/linux.git - Linux kernel stable tree

https://git.kernel.org/stable/c/3b491dd593d582ceeb27aa617600712a6bd14246
generic

sch_cake: Fix out of bounds when parsing TCP options and header - kernel/git/stable/linux.git - Linux kernel stable tree

https://git.kernel.org/stable/c/4cefa061fc63f4d2dff5ab4083f43857cd7a2335
generic

sch_cake: Fix out of bounds when parsing TCP options and header - kernel/git/stable/linux.git - Linux kernel stable tree

https://git.kernel.org/stable/c/595897ef118d6fe66690c4fc5b572028c9da95b7

Weakness Classification(1)

MITRE Common Weakness Enumeration — the root-cause categories this CVE belongs to.

Data Freshness Timeline

(refreshed 13× in last 7d / 46× in last 30d)

Each row is a source pipeline that fetched or updated this CVE on that date, with what changed. For example, "NVD update" means NVD published or revised its analysis for this CVE; "MITRE cvelistV5" means we ingested or refreshed it from the CNA feed. Most recent first.

Showing the most recent 100 of 125 total refreshes for this CVE.

  1. 2026-08-07 16:24 UTCEPSS rescore
  2. 2026-08-06 13:44 UTCEPSS rescore
  3. 2026-08-05 19:15 UTCEPSS rescore
  4. 2026-08-05 09:42 UTCEG score recompute
  5. 2026-08-05 09:41 UTCGHSA enrichment
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  7. 2026-08-04 12:13 UTCEG score recompute
  8. 2026-08-04 12:13 UTCGHSA enrichment
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  11. 2026-08-04 09:52 UTCGHSA enrichment
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  24. 2026-07-23 02:06 UTCEG score recompute
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  75. 2026-06-06 13:46 UTCEPSS rescore

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Frequently asked(5)

What is CVE-2021-47243?
CVE-2021-47243 is a high vulnerability published on May 21, 2024. 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 (cakegettcpopt and caketcphmay_drop) could read one byte out of bounds. When the length is 1, the execution flow gets into the…
When was CVE-2021-47243 disclosed?
CVE-2021-47243 was first published in the National Vulnerability Database on May 21, 2024, with the most recent update on August 5, 2026. EchelonGraph re-ingests CVE updates from NVD on a 2-hour cycle, so this page reflects the latest published state.
Is CVE-2021-47243 actively exploited?
CVE-2021-47243 is not currently on CISA's Known Exploited Vulnerabilities catalog. FIRST EPSS estimates a 0% probability of exploitation in the next 30 days, which ranks it in the top 82.5% of all scored CVEs.
What is the CVSS score of CVE-2021-47243?
CVE-2021-47243 has a CVSS v3 base score of 7.1 (NVD).
How do I remediate CVE-2021-47243?
Patch to the fixed version published by the affected vendor. Where vendor advisories exist for CVE-2021-47243, EchelonGraph cross-links them in the Vendor Advisories panel below — those typically contain the canonical remediation steps, fixed version numbers, and any vendor-specific mitigations.

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