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
Elevated
8.6EG
EchelonGraph verdictPatch this weekExploitation is likely or a public exploit exists.
  • High exploitation likelihood — EPSS 60%
CISA-KEV: Not listedEPSS PROB: 60%CVSS: 8.1Exploit: Elevated riskExposed: 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 PROB
60%
EPSS %ILE
99%
KEV
Not listed

Published

June 11, 2021

Last Modified

November 21, 2024

Advisory Details (7)

Auto-updated Sep 16, 2026
Upstream fix merged — awaiting tagged release. Sources: github_commit.
generic

NetApp Product Security

https://security.netapp.com/advisory/ntap-20210727-0007/
generic

NetApp Product Security

https://security.netapp.com/advisory/ntap-20210723-0001/
generic

HackerOne

https://hackerone.com/reports/1180380
github_commit

commit 7f4a9a9b2a49 (curl/curl)

Fix landed in curl/curl commit 7f4a9a9b2a49 — awaiting tagged release

https://github.com/curl/curl/commit/7f4a9a9b2a49547eae24d2e19bc5c346e9026479
generic

curl - TLS session caching disaster - CVE-2021-22901

https://curl.se/docs/CVE-2021-22901.html
generic
https://cert-portal.siemens.com/productcert/pdf/ssa-732250.pdf
generic
https://cert-portal.siemens.com/productcert/pdf/ssa-389290.pdf

Vendor Advisories for CVE-2021-22901(2)

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

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.

Affected Packages

(13 across 13 ecosystems)
Alpine:v3.12(1)
PackageVulnerable rangeFixed inDependents
curl—7.77.0-r0—
Alpine:v3.13(1)
PackageVulnerable rangeFixed inDependents
curl—7.77.0-r0—
Alpine:v3.14(1)
PackageVulnerable rangeFixed inDependents
curl—7.77.0-r0—
Alpine:v3.15(1)
PackageVulnerable rangeFixed inDependents
curl—7.77.0-r0—
Alpine:v3.16(1)
PackageVulnerable rangeFixed inDependents
curl—7.77.0-r0—
Alpine:v3.17(1)
PackageVulnerable rangeFixed inDependents
curl—7.77.0-r0—
Alpine:v3.18(1)
PackageVulnerable rangeFixed inDependents
curl—7.77.0-r0—
Alpine:v3.19(1)
PackageVulnerable rangeFixed inDependents
curl—7.77.0-r0—
Alpine:v3.20(1)
PackageVulnerable rangeFixed inDependents
curl—7.77.0-r0—
Alpine:v3.21(1)
PackageVulnerable rangeFixed inDependents
curl—7.77.0-r0—
Alpine:v3.22(1)
PackageVulnerable rangeFixed inDependents
curl—7.77.0-r0—
Alpine:v3.23(1)
PackageVulnerable rangeFixed inDependents
curl—7.77.0-r0—
Alpine:v3.24(1)
PackageVulnerable rangeFixed inDependents
curl—7.77.0-r0—

Weakness Classification(1)

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

Additional Vendor Advisories

(1)

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 6× in last 7d / 25× 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 129 total refreshes for this CVE.

  1. 2026-09-18 19:23 UTCEPSS rescore
  2. 2026-09-17 19:23 UTCEPSS rescore
  3. 2026-09-16 14:05 UTCEPSS rescore
  4. 2026-09-16 14:04 UTCEPSS rescore
  5. 2026-09-15 03:06 UTCEPSS rescore
  6. 2026-09-12 14:57 UTCEPSS rescore
  7. 2026-09-11 09:33 UTCEPSS rescore
  8. 2026-09-10 09:29 UTCEPSS rescore
  9. 2026-09-08 21:56 UTCEPSS rescore
  10. 2026-09-06 15:31 UTCOSV refresh
  11. 2026-09-06 13:44 UTCEPSS rescore
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  13. 2026-09-05 15:25 UTCEPSS rescore
  14. 2026-09-04 13:57 UTCEPSS rescore
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  20. 2026-08-28 21:37 UTCEPSS rescore
  21. 2026-08-27 14:22 UTCEPSS rescore
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  24. 2026-08-21 23:46 UTCEPSS rescore
  25. 2026-08-20 22:52 UTCEPSS rescore
Show 75 more
  1. 2026-08-20 01:34 UTCOSV refresh
  2. 2026-08-19 17:01 UTCEPSS rescore
  3. 2026-08-18 13:45 UTCEPSS rescore
  4. 2026-08-17 13:43 UTCEPSS rescore
  5. 2026-08-16 02:11 UTCEPSS rescore
  6. 2026-08-15 01:27 UTCEPSS rescore
  7. 2026-08-13 21:57 UTCEPSS rescore
  8. 2026-08-12 13:47 UTCEPSS rescore
  9. 2026-08-11 13:38 UTCEPSS rescore
  10. 2026-08-08 16:33 UTCEPSS rescore
  11. 2026-08-07 16:23 UTCEPSS rescore
  12. 2026-08-06 13:43 UTCEPSS rescore
  13. 2026-08-04 20:27 UTCOSV refresh
  14. 2026-08-04 15:06 UTCEPSS rescore
  15. 2026-08-04 10:34 UTCEPSS rescore
  16. 2026-07-30 16:25 UTCEPSS rescore
  17. 2026-07-30 01:27 UTCEPSS rescore
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  19. 2026-07-26 14:52 UTCEPSS rescore
  20. 2026-07-25 14:15 UTCEPSS rescore
  21. 2026-07-24 14:15 UTCEPSS rescore
  22. 2026-07-23 14:15 UTCEPSS rescore
  23. 2026-07-23 01:57 UTCEG score recompute▲ 0.50
  24. 2026-07-22 22:44 UTCEG score recompute
  25. 2026-07-22 14:05 UTCEPSS rescore
  26. 2026-07-20 17:04 UTCEPSS rescore
  27. 2026-07-19 14:28 UTCEPSS rescore
  28. 2026-07-18 18:29 UTCOSV refresh
  29. 2026-07-18 10:02 UTCEPSS rescore
  30. 2026-07-16 17:00 UTCEPSS rescore
  31. 2026-07-15 16:55 UTCEPSS rescore
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  33. 2026-07-15 01:57 UTCEPSS rescore
  34. 2026-07-13 22:27 UTCEPSS rescore
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  36. 2026-07-12 05:44 UTCEPSS rescore
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  38. 2026-07-11 08:25 UTCEPSS rescore
  39. 2026-07-09 19:07 UTCEPSS rescore
  40. 2026-07-06 16:25 UTCEPSS rescore
  41. 2026-07-05 02:28 UTCEPSS rescore
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  43. 2026-07-04 06:29 UTCEPSS rescore
  44. 2026-07-04 06:29 UTCEPSS rescore
  45. 2026-07-02 16:57 UTCEPSS rescore
  46. 2026-07-01 15:03 UTCEPSS rescore
  47. 2026-07-01 01:18 UTCOSV refresh
  48. 2026-06-28 04:54 UTCEPSS rescore
  49. 2026-06-28 04:54 UTCEPSS rescore
  50. 2026-06-27 03:06 UTCEPSS rescore
  51. 2026-06-27 03:06 UTCEPSS rescore
  52. 2026-06-25 13:48 UTCEPSS rescore
  53. 2026-06-25 13:48 UTCEPSS rescore
  54. 2026-06-23 21:31 UTCEPSS rescore
  55. 2026-06-23 21:31 UTCEPSS rescore
  56. 2026-06-21 01:58 UTCEPSS rescore
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  58. 2026-06-18 17:51 UTCEPSS rescore
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  60. 2026-06-17 17:51 UTCEPSS rescore
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  62. 2026-06-15 17:46 UTCEPSS rescore
  63. 2026-06-14 23:15 UTCEPSS rescore
  64. 2026-06-13 22:58 UTCEPSS rescore
  65. 2026-06-13 03:43 UTCOSV refresh
  66. 2026-06-12 23:10 UTCEPSS rescore
  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 22:16 UTCEPSS rescore
  71. 2026-06-10 13:20 UTCEPSS rescore
  72. 2026-06-08 14:15 UTCEPSS rescore
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  74. 2026-06-07 15:23 UTCEPSS rescore
  75. 2026-06-07 15:23 UTCEPSS rescore

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 60% probability of exploitation in the next 30 days, which ranks it in the top 0.9% of all scored CVEs.
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

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