CVE-2021-22901

HIGHNVD 8.18.6▲
EchelonGraph scoreHIGH confidence

Score elevated to 8.6 because EPSS predicts 60% probability of exploitation within the next 30 days (top 1.0% of all CVEs). NVD baseline CVSS 8.1 retained for reference. Confidence: see factors.

Triggered by: EPSS exploit prediction ≥85%
Sources: epss, ghsa, nvd
Trending — 3 sources updated this weekElevated
8.1
EchelonGraph verdictPatch this weekExploitation is likely or a public exploit exists.
  • High exploitation likelihood — EPSS 60%
CISA-KEV: Not listedEPSS: 60%CVSS: 8.1Exploit: NoneExposed: 0

A fix is available — apply it.

curl 7.75.0 through 7.76.1 suffers from a use-after-free vulnerability resulting in already freed memory being used when a TLS 1.3 session ticket arrives over a connection. A malicious server can use this in rare unfortunate circumstances to potentially reach remote code execution in the client. When libcurl at run-time sets up support for TLS 1.3 session tickets on a connection using OpenSSL, it stores pointers to the transfer in-memory object for later retrieval when a session ticket arrives. If the connection is used by multiple transfers (like with a reused HTTP/1.1 connection or multiplexed HTTP/2 connection) that first transfer object might be freed before the new session is established on that connection and then the function will access a memory buffer that might be freed. When using that memory, libcurl might even call a function pointer in the object, making it possible for a remote code execution if the server could somehow manage to get crafted memory content into the correct place in memory.

CVSS v3
8.1
EG Score
8.6(high)
EG Risk
67(Track)
EG Risk 67/100SSVC: 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
Severity86% × 45%
Exploitation60% × 40%
Automatability30% × 15%
Action: Routine — remediate on your standard cadence.
EPSS
99.0%
KEV
Not listed

Published

June 11, 2021

Last Modified

November 21, 2024

References (20)

Patch Availability(2)

Vendor / EcosystemFixed in / PatchReleasedSource
redhatjbcs-httpd24-curl2021-06-17redhat
redhatjbcs-httpd24-mod_security-0:2.9.2-63.GA.jbcs.el72021-06-17redhat

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

(3)

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 9× in last 7d / 32× 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.

  1. 2026-07-25 14:15 UTCEPSS rescore
  2. 2026-07-24 14:15 UTCEPSS rescore
  3. 2026-07-23 14:15 UTCEPSS rescore
  4. 2026-07-23 01:57 UTCEG score recompute▲ 0.50
  5. 2026-07-22 22:44 UTCEG score recompute
  6. 2026-07-22 14:05 UTCEPSS rescore
  7. 2026-07-20 17:04 UTCEPSS rescore
  8. 2026-07-19 14:28 UTCEPSS rescore
  9. 2026-07-18 18:29 UTCOSV refresh
  10. 2026-07-18 10:02 UTCEPSS rescore
  11. 2026-07-16 17:00 UTCEPSS rescore
  12. 2026-07-15 16:55 UTCEPSS rescore
  13. 2026-07-15 16:55 UTCEPSS rescore
  14. 2026-07-15 01:57 UTCEPSS rescore
  15. 2026-07-13 22:27 UTCEPSS rescore
  16. 2026-07-13 22:27 UTCEPSS rescore
  17. 2026-07-12 05:44 UTCEPSS rescore
  18. 2026-07-12 05:44 UTCEPSS rescore
  19. 2026-07-11 08:25 UTCEPSS rescore
  20. 2026-07-09 19:07 UTCEPSS rescore
  21. 2026-07-06 16:25 UTCEPSS rescore
  22. 2026-07-05 02:28 UTCEPSS rescore
  23. 2026-07-05 02:28 UTCEPSS rescore
  24. 2026-07-04 06:29 UTCEPSS rescore
  25. 2026-07-04 06:29 UTCEPSS rescore
Show 60 more
  1. 2026-07-02 16:57 UTCEPSS rescore
  2. 2026-07-01 15:03 UTCEPSS rescore
  3. 2026-07-01 01:18 UTCOSV refresh
  4. 2026-06-28 04:54 UTCEPSS rescore
  5. 2026-06-28 04:54 UTCEPSS rescore
  6. 2026-06-27 03:06 UTCEPSS rescore
  7. 2026-06-27 03:06 UTCEPSS rescore
  8. 2026-06-25 13:48 UTCEPSS rescore
  9. 2026-06-25 13:48 UTCEPSS rescore
  10. 2026-06-23 21:31 UTCEPSS rescore
  11. 2026-06-23 21:31 UTCEPSS rescore
  12. 2026-06-21 01:58 UTCEPSS rescore
  13. 2026-06-21 01:57 UTCEPSS rescore
  14. 2026-06-18 17:51 UTCEPSS rescore
  15. 2026-06-18 17:51 UTCEPSS rescore
  16. 2026-06-17 17:51 UTCEPSS rescore
  17. 2026-06-16 17:50 UTCEPSS rescore
  18. 2026-06-15 17:46 UTCEPSS rescore
  19. 2026-06-14 23:15 UTCEPSS rescore
  20. 2026-06-13 22:58 UTCEPSS rescore
  21. 2026-06-13 03:43 UTCOSV refresh
  22. 2026-06-12 23:10 UTCEPSS rescore
  23. 2026-06-12 23:10 UTCEPSS rescore
  24. 2026-06-11 13:58 UTCEPSS rescore
  25. 2026-06-10 22:16 UTCEPSS rescore
  26. 2026-06-10 22:16 UTCEPSS rescore
  27. 2026-06-10 13:20 UTCEPSS rescore
  28. 2026-06-08 14:15 UTCEPSS rescore
  29. 2026-06-08 14:15 UTCEPSS rescore
  30. 2026-06-07 15:23 UTCEPSS rescore
  31. 2026-06-07 15:23 UTCEPSS rescore
  32. 2026-06-06 13:46 UTCEPSS rescore
  33. 2026-06-06 13:46 UTCEPSS rescore
  34. 2026-06-06 13:46 UTCEPSS rescore
  35. 2026-06-05 22:45 UTCEPSS rescore
  36. 2026-06-05 22:45 UTCEPSS rescore
  37. 2026-06-05 06:09 UTCEPSS rescore
  38. 2026-06-05 06:09 UTCEPSS rescore
  39. 2026-06-05 06:08 UTCEPSS rescore
  40. 2026-06-04 13:10 UTCEPSS rescore
  41. 2026-06-02 20:11 UTCEPSS rescore
  42. 2026-06-02 20:11 UTCEPSS rescore
  43. 2026-06-01 13:50 UTCEPSS rescore
  44. 2026-06-01 13:50 UTCEPSS rescore
  45. 2026-05-31 22:29 UTCEPSS rescore
  46. 2026-05-31 22:29 UTCEPSS rescore
  47. 2026-05-31 00:15 UTCEPSS rescore
  48. 2026-05-31 00:15 UTCEPSS rescore
  49. 2026-05-29 13:42 UTCEPSS rescore
  50. 2026-05-28 13:43 UTCEPSS rescore
  51. 2026-05-28 13:43 UTCEPSS rescore
  52. 2026-05-27 13:39 UTCEPSS rescore
  53. 2026-05-26 15:00 UTCEG score recompute
  54. 2026-05-26 15:00 UTCVendor advisory
  55. 2026-05-26 15:00 UTCGHSA enrichment
  56. 2026-05-26 13:42 UTCEPSS rescore
  57. 2026-05-26 13:42 UTCEPSS rescore
  58. 2026-05-26 07:17 UTCEPSS rescore
  59. 2026-05-26 07:17 UTCEPSS rescore
  60. 2026-05-24 16:49 UTCEPSS rescore

Related CVEs(same vendor + same CWE)

Frequently asked(5)

What is CVE-2021-22901?
CVE-2021-22901 is a high vulnerability published on June 11, 2021. curl 7.75.0 through 7.76.1 suffers from a use-after-free vulnerability resulting in already freed memory being used when a TLS 1.3 session ticket arrives over a connection. A malicious server can use this in rare unfortunate circumstances to potentially reach remote code execution in the client.…
When was CVE-2021-22901 disclosed?
CVE-2021-22901 was first published in the National Vulnerability Database on June 11, 2021, with the most recent update on November 21, 2024. EchelonGraph re-ingests CVE updates from NVD on a 2-hour cycle, so this page reflects the latest published state.
Is CVE-2021-22901 actively exploited?
CVE-2021-22901 is not currently on CISA's Known Exploited Vulnerabilities catalog. FIRST EPSS estimates a 99.0% percentile likelihood of exploitation in the next 30 days — higher percentiles indicate greater predicted risk.
What is the CVSS score of CVE-2021-22901?
CVE-2021-22901 has a CVSS v3 base score of 8.1 (NVD). EchelonGraph synthesises NVD + CISA KEV + FIRST EPSS + GHSA into a combined EG score of 8.6.
How do I remediate CVE-2021-22901?
Patch to the fixed version published by the affected vendor. Where vendor advisories exist for CVE-2021-22901, 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-2021-22901

Explore →

Is Your Infrastructure Affected by CVE-2021-22901?

EchelonGraph automatically scans your cloud infrastructure and maps CVE exposure using blast radius analysis.

Start Free Scan →Browse All CVEs