CVE-2021-22555

HIGHNVD 8.39.0▲
EchelonGraph scoreHIGH confidence

Score elevated to 9.0 because this CVE is listed on the CISA Known Exploited Vulnerabilities catalog (added 2025-10-06), indicating real-world exploitation has been confirmed by US federal agencies. NVD baseline CVSS 8.3 retained for reference. Confidence: HIGH.

Triggered by: CISA KEV (actively exploited)
Sources: cisa_kev, epss, nvd
Trending — 4 sources updated this weekExploited in the wild
8.3
EchelonGraph verdictPatch nowTreat as an emergency — this is being exploited.
  • Actively exploited in the wild (CISA-KEV)
CISA-KEV: ExploitedEPSS: 79%CVSS: 8.3Exploit: NoneExposed: 0

A fix is available — apply it.

A heap out-of-bounds write affecting Linux since v2.6.19-rc1 was discovered in net/netfilter/x_tables.c. This allows an attacker to gain privileges or cause a DoS (via heap memory corruption) through user name space

CVSS v3
8.3
EG Score
9.0(high)
EG Risk
81(Attend)
EG Risk 81/100SSVC: Attend

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
Severity90% × 45%
Exploitation100% × 40%
Automatability0% × 15%
Action: Remediate soon — notable exploitation risk.
EPSS
99.5%
KEV
⚠ Exploited

Published

July 7, 2021

Last Modified

October 27, 2025

Advisory Details (9)

Auto-updated Jun 2, 2026
🔬 Proof of concept available. Patch available. Sources: github.
generic

Packet Storm

http://packetstormsecurity.com/files/163528/Linux-Kernel-Netfilter-Heap-Out-Of-Bounds-Write.html
generic

NetApp Product Security

https://security.netapp.com/advisory/ntap-20210805-0010/
github Patch Available🟡 PoC Available

Linux: Heap Out-Of-Bounds Write in xt_compat_target_from_user · Advisory · google/security-research · GitHub

https://github.com/google/security-research/security/advisories/GHSA-xxx5-8mvq-3528
generic

netfilter: x_tables: fix compat match/target pad out-of-bound write - kernel/git/torvalds/linux.git - Linux kernel source tree

https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/net/netfilter/x_tables.c?id=b29c457a6511435960115c0f548c4360d5f4801d
generic

[NETFILTER]: x_tables: simplify compat API - kernel/git/torvalds/linux.git - Linux kernel source tree

https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/net/netfilter/x_tables.c?id=9fa492cdc160cd27ce1046cb36f47d3b2b1efa21
generic

Packet Storm

http://packetstormsecurity.com/files/165477/Kernel-Live-Patch-Security-Notice-LSN-0083-1.html
generic

Packet Storm

http://packetstormsecurity.com/files/164437/Netfilter-x_tables-Heap-Out-Of-Bounds-Write-Privilege-Escalation.html
generic

Packet Storm

http://packetstormsecurity.com/files/164155/Kernel-Live-Patch-Security-Notice-LSN-0081-1.html
generic

Packet Storm

http://packetstormsecurity.com/files/163878/Kernel-Live-Patch-Security-Notice-LSN-0080-1.html

Vendor Advisories for CVE-2021-22555(20)

These vendors published their own advisory mentioning this CVE — often with vendor-specific remediation steps + affected product lists not in NVD.

Patch Availability(19)

Vendor / EcosystemFixed in / PatchReleasedSource
ubuntuoem (4.15.0-1063) @ bionic2026-07-21ubuntu
ubuntulowlatency-4.4 (4.4.0-168) @ xenial2026-07-21ubuntu
ubuntuvlan-modules-4.4.0-213-generic-di (4.4.0-213.245) @ xenial2026-07-21ubuntu
redhatkernel-0:2.6.32-754.58.1.el62025-10-10redhat
redhatkpatch-patch2021-10-12redhat
redhatkernel-0:3.10.0-957.84.1.el72021-10-12redhat
redhatkernel-0:3.10.0-693.94.1.el72021-10-05redhat
redhatkernel-0:3.10.0-1062.56.1.el72021-09-14redhat
redhatredhat-virtualization-host-0:4.3.18-20210903.0.el7_92021-09-09redhat
redhatkernel-0:3.10.0-1160.41.1.el72021-08-31redhat
redhatkernel-0:4.18.0-193.64.1.el8_22021-08-31redhat
redhatkernel-rt-0:4.18.0-193.64.1.rt13.115.el8_22021-08-31redhat
redhatkernel-0:3.10.0-514.92.1.el72021-08-31redhat
redhatkernel-0:3.10.0-327.100.1.el72021-08-31redhat
redhatkernel-rt-0:3.10.0-1160.41.1.rt56.1181.el72021-08-31redhat
redhatredhat-virtualization-host-0:4.4.7-20210804.0.el8_42021-08-19redhat
redhatkernel-0:4.18.0-147.52.1.el8_12021-08-17redhat
redhatkernel-rt-0:4.18.0-305.12.1.rt7.84.el8_42021-08-10redhat
redhatkernel-0:4.18.0-305.12.1.el8_42021-08-10redhat

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.

Additional Vendor Advisories

(5)

Vendors that published advisories for this CVE beyond the curated set above. Broader coverage but minimal per-row detail — click through for the original advisory.

Data Freshness Timeline

(refreshed 51× in last 7d / 209× 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 389 total refreshes for this CVE.

  1. 2026-07-23 01:57 UTCEG score recompute
  2. 2026-07-22 22:17 UTCEG score recompute
  3. 2026-07-22 22:17 UTCVendor advisory
  4. 2026-07-22 19:40 UTCCISA KEV update
  5. 2026-07-22 18:04 UTCEG score recompute
  6. 2026-07-22 18:04 UTCVendor advisory
  7. 2026-07-22 14:05 UTCEPSS rescore
  8. 2026-07-22 13:49 UTCVendor advisory
  9. 2026-07-22 09:35 UTCVendor advisory
  10. 2026-07-22 05:20 UTCVendor advisory
  11. 2026-07-22 01:06 UTCVendor advisory
  12. 2026-07-21 20:52 UTCVendor advisory
  13. 2026-07-21 16:36 UTCEG score recompute
  14. 2026-07-21 16:36 UTCVendor advisory
  15. 2026-07-21 15:22 UTCEPSS rescore
  16. 2026-07-21 15:22 UTCEPSS rescore
  17. 2026-07-21 14:37 UTCCISA KEV update
  18. 2026-07-21 12:22 UTCVendor advisory
  19. 2026-07-21 08:09 UTCVendor advisory
  20. 2026-07-21 03:56 UTCVendor advisory
  21. 2026-07-20 23:42 UTCVendor advisory
  22. 2026-07-20 19:28 UTCVendor advisory
  23. 2026-07-20 15:15 UTCVendor advisory
  24. 2026-07-20 11:01 UTCVendor advisory
  25. 2026-07-20 06:46 UTCVendor advisory
Show 75 more
  1. 2026-07-20 01:50 UTCVendor advisory
  2. 2026-07-19 21:36 UTCVendor advisory
  3. 2026-07-19 17:23 UTCVendor advisory
  4. 2026-07-19 13:08 UTCVendor advisory
  5. 2026-07-19 08:55 UTCVendor advisory
  6. 2026-07-19 04:41 UTCEG score recompute
  7. 2026-07-19 04:41 UTCVendor advisory
  8. 2026-07-19 02:26 UTCEPSS rescore
  9. 2026-07-19 00:28 UTCVendor advisory
  10. 2026-07-18 20:14 UTCVendor advisory
  11. 2026-07-18 16:00 UTCVendor advisory
  12. 2026-07-18 11:46 UTCVendor advisory
  13. 2026-07-18 07:31 UTCVendor advisory
  14. 2026-07-18 03:17 UTCVendor advisory
  15. 2026-07-17 23:03 UTCVendor advisory
  16. 2026-07-17 18:48 UTCVendor advisory
  17. 2026-07-17 14:35 UTCVendor advisory
  18. 2026-07-17 10:19 UTCEG score recompute
  19. 2026-07-17 10:19 UTCVendor advisory
  20. 2026-07-17 06:05 UTCVendor advisory
  21. 2026-07-17 01:51 UTCVendor advisory
  22. 2026-07-16 21:37 UTCVendor advisory
  23. 2026-07-16 17:23 UTCVendor advisory
  24. 2026-07-16 17:04 UTCCISA KEV update
  25. 2026-07-16 13:09 UTCVendor advisory
  26. 2026-07-16 08:55 UTCVendor advisory
  27. 2026-07-16 04:41 UTCVendor advisory
  28. 2026-07-16 00:27 UTCVendor advisory
  29. 2026-07-15 20:14 UTCVendor advisory
  30. 2026-07-15 16:55 UTCEPSS rescore
  31. 2026-07-15 16:55 UTCEPSS rescore
  32. 2026-07-15 16:49 UTCCISA KEV update
  33. 2026-07-15 16:00 UTCVendor advisory
  34. 2026-07-15 15:04 UTCCISA KEV update
  35. 2026-07-15 11:47 UTCVendor advisory
  36. 2026-07-15 07:33 UTCVendor advisory
  37. 2026-07-15 03:18 UTCVendor advisory
  38. 2026-07-14 23:03 UTCVendor advisory
  39. 2026-07-14 18:49 UTCVendor advisory
  40. 2026-07-14 18:05 UTCCISA KEV update
  41. 2026-07-14 14:33 UTCVendor advisory
  42. 2026-07-14 10:20 UTCVendor advisory
  43. 2026-07-14 06:05 UTCVendor advisory
  44. 2026-07-14 01:50 UTCVendor advisory
  45. 2026-07-13 22:27 UTCEPSS rescore
  46. 2026-07-13 22:27 UTCEPSS rescore
  47. 2026-07-13 21:37 UTCVendor advisory
  48. 2026-07-13 17:23 UTCVendor advisory
  49. 2026-07-13 17:07 UTCCISA KEV update
  50. 2026-07-13 13:09 UTCVendor advisory
  51. 2026-07-13 08:55 UTCVendor advisory
  52. 2026-07-13 04:41 UTCVendor advisory
  53. 2026-07-13 00:28 UTCVendor advisory
  54. 2026-07-12 20:14 UTCVendor advisory
  55. 2026-07-12 16:00 UTCVendor advisory
  56. 2026-07-12 11:46 UTCVendor advisory
  57. 2026-07-12 07:32 UTCVendor advisory
  58. 2026-07-12 03:18 UTCVendor advisory
  59. 2026-07-11 23:04 UTCVendor advisory
  60. 2026-07-11 18:51 UTCVendor advisory
  61. 2026-07-11 14:37 UTCVendor advisory
  62. 2026-07-11 10:23 UTCVendor advisory
  63. 2026-07-11 08:25 UTCEPSS rescore
  64. 2026-07-11 06:10 UTCVendor advisory
  65. 2026-07-11 01:55 UTCVendor advisory
  66. 2026-07-10 21:42 UTCVendor advisory
  67. 2026-07-10 17:52 UTCCISA KEV update
  68. 2026-07-10 17:29 UTCVendor advisory
  69. 2026-07-10 13:15 UTCVendor advisory
  70. 2026-07-10 08:59 UTCVendor advisory
  71. 2026-07-10 04:45 UTCVendor advisory
  72. 2026-07-10 00:32 UTCVendor advisory
  73. 2026-07-09 20:15 UTCVendor advisory
  74. 2026-07-09 16:02 UTCVendor advisory
  75. 2026-07-09 11:47 UTCVendor advisory

Publicly available exploits

(6 references)

Working exploit code is in the public domain (1 Metasploit module) (4 GitHub PoCs) (1 Exploit-DB entry). Defenders should treat patch urgency accordingly — public PoCs typically lead to mass-exploitation within 24-72 hours.

  • GitHub PoCtukru/CVE-2021-22555
    First seen Aug 5, 2023

    This repo hosts TUKRU's Linux Privilege Escalation exploit (CVE-2021-22555). It demonstrates gaining root privileges via a vulnerability. Tested on Ubuntu 5.8.0-48-generic and COS 5.4.89+. Use responsibly and ethically.

    Open source ↗
  • GitHub PoCveritas501/CVE-2021-22555-PipeVersion
    First seen Apr 5, 2022

    CVE-2021-22555 exploit rewritten with pipe primitive

    Open source ↗
  • GitHub PoCxyjl-ly/CVE-2021-22555-Exploit
    First seen Jul 16, 2021

    CVE-2021-22555 Exploit

    Open source ↗
  • GitHub PoCcgwalters/container-cve-2021-22555
    First seen Jul 16, 2021
    Open source ↗
  • Exploit-DBEDB-50135✓ verified
    First seen Jul 15, 2021

    Linux Kernel 2.6.19 < 5.9 - 'Netfilter Local Privilege Escalation

    Open source ↗
  • Metasploitexploit/linux/local/netfilter_xtables_heap_oob_write_priv_esc✓ verified
    First seen Jul 7, 2021

    Netfilter x_tables Heap OOB Write Privilege Escalation

    Open source ↗

Related CVEs(same vendor + same CWE)

Frequently asked(6)

What is CVE-2021-22555?
CVE-2021-22555 is a high vulnerability published on July 7, 2021. A heap out-of-bounds write affecting Linux since v2.6.19-rc1 was discovered in net/netfilter/x_tables.c. This allows an attacker to gain privileges or cause a DoS (via heap memory corruption) through user name space
When was CVE-2021-22555 disclosed?
CVE-2021-22555 was first published in the National Vulnerability Database on July 7, 2021, with the most recent update on October 27, 2025. EchelonGraph re-ingests CVE updates from NVD on a 2-hour cycle, so this page reflects the latest published state.
Is CVE-2021-22555 actively exploited?
Yes. CISA added CVE-2021-22555 to the Known Exploited Vulnerabilities catalog on October 6, 2025, affecting Linux Kernel. KEV listing indicates confirmed exploitation in the wild; this CVE warrants immediate patching attention.
What is the CVSS score of CVE-2021-22555?
CVE-2021-22555 has a CVSS v3 base score of 8.3 (NVD). EchelonGraph synthesises NVD + CISA KEV + FIRST EPSS + GHSA into a combined EG score of 9.0.
Which products are affected by CVE-2021-22555?
CVE-2021-22555 affects Linux Kernel. The full affected-products list, including version ranges and fixed versions, is shown in the Affected Packages section of this page.
How do I remediate CVE-2021-22555?
Patch to the fixed version published by the affected vendor. Where vendor advisories exist for CVE-2021-22555, 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.

Dependency Blast Radius

Explore the affected products and dependency analysis for CVE-2021-22555

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