CVE-2021-47245

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 — 4 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: 1%CVSS: 7.1Exploit: None knownExposed: 0

A fix is available — apply it.

In the Linux kernel, the following vulnerability has been resolved:

netfilter: synproxy: Fix out of bounds when parsing TCP options

The TCP option parser in synproxy (synproxy_parse_options) 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 an early return when length < 0 to avoid calling skb_header_pointer with negative length.

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%
Exploitation1% × 40%
Automatability0% × 15%
Action: Routine — remediate on your standard cadence.
EPSS PROB
1%
EPSS %ILE
52%
KEV
Not listed

Published

May 21, 2024

Last Modified

August 5, 2026

Advisory Details (8)

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

netfilter: synproxy: Fix out of bounds when parsing TCP options - kernel/git/stable/linux.git - Linux kernel stable tree

https://git.kernel.org/stable/c/5fc177ab759418c9537433e63301096e733fb915
generic

netfilter: synproxy: Fix out of bounds when parsing TCP options - kernel/git/stable/linux.git - Linux kernel stable tree

https://git.kernel.org/stable/c/f648089337cb8ed40b2bb96e244f72b9d97dc96b
generic

netfilter: synproxy: Fix out of bounds when parsing TCP options - kernel/git/stable/linux.git - Linux kernel stable tree

https://git.kernel.org/stable/c/9cdf299ba4e153b5e56187648420de22c6216f02
generic

netfilter: synproxy: Fix out of bounds when parsing TCP options - kernel/git/stable/linux.git - Linux kernel stable tree

https://git.kernel.org/stable/c/6defc77d48eff74075b80ad5925061b2fc010d98
generic

netfilter: synproxy: Fix out of bounds when parsing TCP options - kernel/git/stable/linux.git - Linux kernel stable tree

https://git.kernel.org/stable/c/7d9a9a1a88a3da574e019b4de756bc73337b3b0b
generic

netfilter: synproxy: Fix out of bounds when parsing TCP options - kernel/git/stable/linux.git - Linux kernel stable tree

https://git.kernel.org/stable/c/674b5f0c6a4fc5d3abce877048290cea6091fcb1
generic

netfilter: synproxy: Fix out of bounds when parsing TCP options - kernel/git/stable/linux.git - Linux kernel stable tree

https://git.kernel.org/stable/c/576c1526b4d83c44ad7b673cb841f36cbc6cb6c4
generic

netfilter: synproxy: Fix out of bounds when parsing TCP options - kernel/git/stable/linux.git - Linux kernel stable tree

https://git.kernel.org/stable/c/e1eb98cfeafdd85537e7e3cefe93ca9bfbcc3ea8

Patch Availability(4)

Vendor / EcosystemFixed in / PatchReleasedSource
ubuntulinux-tools-fips (4.4.0.1113.114) @ xenial2026-05-24ubuntu
ubuntulinux-tools-aws (4.4.0.1143.140) @ trusty2026-05-24ubuntu
ubuntulinux-virtual-lts-xenial (4.4.0.268.274) @ xenial2026-05-24ubuntu
ubuntulinux-virtual-lts-xenial (4.4.0.268.302~14.04.1) @ trusty2026-05-24ubuntu

Patches are aggregated from vendor advisories (Red Hat, Microsoft, Cisco, GitHub) and package ecosystems (OSV, GHSA). Multiple rows for the same upstream release have been deduplicated.

Weakness Classification(1)

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

All Vendor Advisories

(4)

Every vendor that published an advisory referencing this CVE — pulled from our cve_vendor_advisories aggregation. Click any row for the vendor's original advisory page.

Data Freshness Timeline

(refreshed 15× in last 7d / 48× 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 124 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 09:41 UTCEG score recompute
  5. 2026-08-05 09:41 UTCGHSA enrichment
  6. 2026-08-04 15:06 UTCEPSS rescore
  7. 2026-08-04 12:12 UTCEG score recompute
  8. 2026-08-04 12:12 UTCVendor advisory
  9. 2026-08-04 12:12 UTCGHSA enrichment
  10. 2026-08-04 10:34 UTCEPSS rescore
  11. 2026-08-04 09:52 UTCEG score recompute
  12. 2026-08-04 09:52 UTCVendor advisory
  13. 2026-08-04 09:52 UTCGHSA enrichment
  14. 2026-08-03 10:33 UTCEPSS rescore
  15. 2026-08-02 02:24 UTCEPSS rescore
  16. 2026-08-01 04:13 UTCEPSS rescore
  17. 2026-08-01 02:42 UTCOSV refresh
  18. 2026-07-30 16:25 UTCEPSS rescore
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  20. 2026-07-28 15:33 UTCEPSS rescore
  21. 2026-07-26 14:52 UTCEPSS rescore
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  1. 2026-07-23 02:06 UTCEG score recompute
  2. 2026-07-22 22:53 UTCEG score recompute
  3. 2026-07-22 14:06 UTCEPSS rescore
  4. 2026-07-21 15:22 UTCEPSS rescore
  5. 2026-07-21 15:22 UTCEPSS rescore
  6. 2026-07-20 17:05 UTCEPSS rescore
  7. 2026-07-19 14:29 UTCEPSS rescore
  8. 2026-07-19 02:27 UTCEPSS rescore
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  10. 2026-07-18 10:02 UTCEPSS rescore
  11. 2026-07-16 17:00 UTCEPSS rescore
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  13. 2026-07-15 16:55 UTCEPSS rescore
  14. 2026-07-15 01:58 UTCEPSS rescore
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  16. 2026-07-14 09:55 UTCOSV refresh
  17. 2026-07-13 22:27 UTCEPSS rescore
  18. 2026-07-13 06:11 UTCEPSS rescore
  19. 2026-07-13 06:11 UTCEPSS rescore
  20. 2026-07-12 05:44 UTCEPSS rescore
  21. 2026-07-11 08:25 UTCEPSS rescore
  22. 2026-07-09 19:07 UTCEPSS rescore
  23. 2026-07-09 19:07 UTCEPSS rescore
  24. 2026-07-08 15:12 UTCEPSS rescore
  25. 2026-07-08 15:12 UTCEPSS rescore
  26. 2026-07-07 13:43 UTCEPSS rescore
  27. 2026-07-06 16:25 UTCEPSS rescore
  28. 2026-07-06 16:25 UTCEPSS rescore
  29. 2026-07-06 02:21 UTCEPSS rescore
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  31. 2026-07-05 02:28 UTCEPSS rescore
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  36. 2026-06-30 23:20 UTCEPSS rescore
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  40. 2026-06-28 04:54 UTCEPSS rescore
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  42. 2026-06-27 03:07 UTCEPSS rescore
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  44. 2026-06-26 10:37 UTCOSV refresh
  45. 2026-06-25 13:48 UTCEPSS rescore
  46. 2026-06-25 13:48 UTCEPSS rescore
  47. 2026-06-24 14:03 UTCEPSS rescore
  48. 2026-06-24 14:03 UTCEPSS rescore
  49. 2026-06-23 21:31 UTCEPSS rescore
  50. 2026-06-23 21:31 UTCEPSS rescore
  51. 2026-06-22 14:24 UTCEPSS rescore
  52. 2026-06-21 14:55 UTCEPSS rescore
  53. 2026-06-21 01:58 UTCEPSS rescore
  54. 2026-06-21 01:58 UTCEPSS rescore
  55. 2026-06-19 19:24 UTCEPSS rescore
  56. 2026-06-19 19:24 UTCEPSS rescore
  57. 2026-06-18 17:51 UTCEPSS rescore
  58. 2026-06-18 17:51 UTCEPSS rescore
  59. 2026-06-17 17:51 UTCEPSS rescore
  60. 2026-06-17 17:51 UTCEPSS rescore
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  63. 2026-06-14 23:15 UTCEPSS rescore
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  65. 2026-06-13 22:58 UTCEPSS rescore
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  67. 2026-06-12 23:10 UTCEPSS rescore
  68. 2026-06-11 13:58 UTCEPSS rescore
  69. 2026-06-10 22:16 UTCEPSS rescore
  70. 2026-06-10 13:20 UTCEPSS rescore
  71. 2026-06-08 17:11 UTCOSV refresh
  72. 2026-06-08 14:15 UTCEPSS rescore
  73. 2026-06-08 14:15 UTCEPSS rescore
  74. 2026-06-08 14:15 UTCEPSS rescore
  75. 2026-06-07 15:23 UTCEPSS rescore

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Frequently asked(5)

What is CVE-2021-47245?
CVE-2021-47245 is a high vulnerability published on May 21, 2024. In the Linux kernel, the following vulnerability has been resolved: netfilter: synproxy: Fix out of bounds when parsing TCP options The TCP option parser in synproxy (synproxyparseoptions) could read one byte out of bounds. When the length is 1, the execution flow gets into the loop, reads one byte…
When was CVE-2021-47245 disclosed?
CVE-2021-47245 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-2021-47245 actively exploited?
CVE-2021-47245 is not currently on CISA's Known Exploited Vulnerabilities catalog. FIRST EPSS estimates a 1% probability of exploitation in the next 30 days, which ranks it in the top 47.6% of all scored CVEs.
What is the CVSS score of CVE-2021-47245?
CVE-2021-47245 has a CVSS v3 base score of 7.1 (NVD).
How do I remediate CVE-2021-47245?
Patch to the fixed version published by the affected vendor. Where vendor advisories exist for CVE-2021-47245, 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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