CVE-2021-23840

HIGHNVD 7.58.1▲
EchelonGraph scoreHIGH confidence

Score elevated to 8.1 because EPSS predicts 51% probability of exploitation within the next 30 days (98th percentile of EPSS-scored CVEs). NVD baseline CVSS 7.5 retained for reference. Confidence: see factors.

Triggered by: EPSS exploit prediction (continuous uplift above 30%)
Sources: epss, nvd
Elevated
8.1EG
EchelonGraph verdictPatch this weekExploitation is likely or a public exploit exists.
  • High exploitation likelihood — EPSS 51%
CISA-KEV: Not listedEPSS PROB: 51%CVSS: 7.5Exploit: Elevated riskExposed services: Not assessed

A fix is available — apply it.

Calls to EVP_CipherUpdate, EVP_EncryptUpdate and EVP_DecryptUpdate may overflow the output length argument in some cases where the input length is close to the maximum permissable length for an integer on the platform. In such cases the return value from the function call will be 1 (indicating success), but the output length value will be negative. This could cause applications to behave incorrectly or crash. OpenSSL versions 1.1.1i and below are affected by this issue. Users of these versions should upgrade to OpenSSL 1.1.1j. OpenSSL versions 1.0.2x and below are affected by this issue. However OpenSSL 1.0.2 is out of support and no longer receiving public updates. Premium support customers of OpenSSL 1.0.2 should upgrade to 1.0.2y. Other users should upgrade to 1.1.1j. Fixed in OpenSSL 1.1.1j (Affected 1.1.1-1.1.1i). Fixed in OpenSSL 1.0.2y (Affected 1.0.2-1.0.2x).

CVSS v3
7.5
EG Score
8.1HIGHhigh confidence
EG Risk
72
EG Risk 72/100CISA SSVC

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
Severity81% × 45%
Exploitation51% × 40%
Automatability100% × 15%
CISA SSVC: Track at low or medium mission impact; Attend at high (mission-essential systems).
Action: A fix is available. Apply it within your standard update timelines at low or medium mission impact and sooner than that at high.
EPSS PROB
51%
EPSS %ILE
98th
KEV
Not listed

CISA SSVCTrack at low or medium mission impact; Attend at high (mission-essential systems).

A fix is available. Apply it within your standard update timelines at low or medium mission impact and sooner than that at high.

Exploitation none (CISA Vulnrichment) · Automatable yes (CISA Vulnrichment) · Technical impact partial (CISA Vulnrichment). Mission impact is CISA's Mission & Well-being decision point, and only you can judge it: high means the affected system is essential to your organisation's mission, or its compromise could cause irreversible harm to people. CISA's decision table

Published

February 16, 2021

Last Modified

April 16, 2026

References (40)

Vendor Advisories for CVE-2021-23840(7)

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

Patch Availability(10)

Vendor / EcosystemFix (by version range) / PatchReleasedSource
ubuntuopenssl (1.0.2g-1ubuntu4.19) @ xenial2026-05-22ubuntu
ubuntuopenssl (1.0.1f-1ubuntu2.27+esm10) @ trusty2026-05-22ubuntu
ubuntuovmf (2020.11-4ubuntu0.1) @ hirsute2026-05-22ubuntu
redhatpatch2021-11-30redhat
redhatjws5-tomcat-vault-0:1.1.8-4.Final_redhat_00004.1.el8jws2021-11-30redhat
redhatopenssl2021-11-10redhat
redhatjbcs-httpd24-openssl-pkcs11-0:0.4.10-22.jbcs.el72021-11-10redhat
redhatopenssl-1:1.1.1k-4.el82021-11-09redhat
redhatedk2-0:20210527gite1999b264f1f-3.el82021-11-09redhat
redhatopenssl-1:1.0.2k-22.el7_92021-10-12redhat

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

(26 across 23 ecosystems)
Alpine:v3.15(2)
PackageVulnerable rangeFix by version rangeDependents
openssl—
  • 1.0.2 up to 1.1.1j-r0: fixed in 1.1.1j-r0
—
openssl3—
  • every version up to 1.1.1j-r0: fixed in 1.1.1j-r0
—
Alpine:v3.16(2)
PackageVulnerable rangeFix by version rangeDependents
openssl—
  • 1.0.2 up to 1.1.1j-r0: fixed in 1.1.1j-r0
—
openssl3—
  • every version up to 1.1.1j-r0: fixed in 1.1.1j-r0
—
Debian:9(2)
PackageVulnerable rangeFix by version rangeDependents
openssl1.1.0f-3 ... 1.1.0l-1~deb9u2 (16 versions)
  • every version up to 1.1.0l-1~deb9u3: fixed in 1.1.0l-1~deb9u3
—
openssl1.01.0.2l-2 ... 1.0.2u-1~deb9u3 (20 versions)
  • every version up to 1.0.2u-1~deb9u4: fixed in 1.0.2u-1~deb9u4
—
Alpine:v3.10(1)
PackageVulnerable rangeFix by version rangeDependents
openssl—
  • 1.0.2 up to 1.1.1j-r0: fixed in 1.1.1j-r0
—
Alpine:v3.11(1)
PackageVulnerable rangeFix by version rangeDependents
openssl—
  • 1.0.2 up to 1.1.1j-r0: fixed in 1.1.1j-r0
—
Alpine:v3.12(1)
PackageVulnerable rangeFix by version rangeDependents
openssl—
  • 1.0.2 up to 1.1.1j-r0: fixed in 1.1.1j-r0
—
Alpine:v3.13(1)
PackageVulnerable rangeFix by version rangeDependents
openssl—
  • 1.0.2 up to 1.1.1j-r0: fixed in 1.1.1j-r0
—
Alpine:v3.14(1)
PackageVulnerable rangeFix by version rangeDependents
openssl—
  • 1.0.2 up to 1.1.1j-r0: fixed in 1.1.1j-r0
—
Alpine:v3.17(1)
PackageVulnerable rangeFix by version rangeDependents
openssl—
  • 1.0.2 up to 1.1.1j-r0: fixed in 1.1.1j-r0
—
Alpine:v3.18(1)
PackageVulnerable rangeFix by version rangeDependents
openssl—
  • 1.0.2 up to 1.1.1j-r0: fixed in 1.1.1j-r0
—
Alpine:v3.19(1)
PackageVulnerable rangeFix by version rangeDependents
openssl—
  • 1.0.2 up to 1.1.1j-r0: fixed in 1.1.1j-r0
—
Alpine:v3.20(1)
PackageVulnerable rangeFix by version rangeDependents
openssl—
  • 1.0.2 up to 1.1.1j-r0: fixed in 1.1.1j-r0
—
Alpine:v3.21(1)
PackageVulnerable rangeFix by version rangeDependents
openssl—
  • 1.0.2 up to 1.1.1j-r0: fixed in 1.1.1j-r0
—
Alpine:v3.22(1)
PackageVulnerable rangeFix by version rangeDependents
openssl—
  • 1.0.2 up to 1.1.1j-r0: fixed in 1.1.1j-r0
—
Alpine:v3.23(1)
PackageVulnerable rangeFix by version rangeDependents
openssl—
  • 1.0.2 up to 1.1.1j-r0: fixed in 1.1.1j-r0
—
Alpine:v3.24(1)
PackageVulnerable rangeFix by version rangeDependents
openssl—
  • 1.0.2 up to 1.1.1j-r0: fixed in 1.1.1j-r0
—
Alpine:v3.9(1)
PackageVulnerable rangeFix by version rangeDependents
openssl—
  • 1.0.2 up to 1.1.1j-r0: fixed in 1.1.1j-r0
—
crates.io(1)
PackageVulnerable rangeFix by version rangeDependents
openssl-src—
  • every version up to 111.14.0: fixed in 111.14.0
  • 0.0.0-0 up to 111.14.0: fixed in 111.14.0
—
Debian:10(1)
PackageVulnerable rangeFix by version rangeDependents
openssl1.1.1c-1, 1.1.1d-0+deb10u1, 1.1.1d-0+deb10u2, 1.1.1d-0+deb10u3, 1.1.1d-0+deb10u4
  • every version up to 1.1.1d-0+deb10u5: fixed in 1.1.1d-0+deb10u5
—
Debian:11(1)
PackageVulnerable rangeFix by version rangeDependents
openssl—
  • every version up to 1.1.1j-1: fixed in 1.1.1j-1
—
Debian:12(1)
PackageVulnerable rangeFix by version rangeDependents
openssl—
  • every version up to 1.1.1j-1: fixed in 1.1.1j-1
—
Debian:13(1)
PackageVulnerable rangeFix by version rangeDependents
openssl—
  • every version up to 1.1.1j-1: fixed in 1.1.1j-1
—
Debian:14(1)
PackageVulnerable rangeFix by version rangeDependents
openssl—
  • every version up to 1.1.1j-1: fixed in 1.1.1j-1
—

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 5× in last 7d / 27× 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 188 total refreshes for this CVE.

  1. 2026-10-09 20:04 UTCEPSS rescore
  2. 2026-10-08 16:39 UTCEPSS rescore
  3. 2026-10-07 23:44 UTCEPSS rescore
  4. 2026-10-07 19:54 UTCOSV refresh
  5. 2026-10-06 15:13 UTCEPSS rescore
  6. 2026-10-03 14:22 UTCEPSS rescore
  7. 2026-10-03 14:22 UTCEPSS rescore
  8. 2026-10-02 16:22 UTCEPSS rescore
  9. 2026-10-01 19:46 UTCEPSS rescore
  10. 2026-09-30 15:31 UTCEG score recompute
  11. 2026-09-27 13:41 UTCEPSS rescore
  12. 2026-09-26 15:54 UTCEPSS rescore
  13. 2026-09-26 15:54 UTCEPSS rescore
  14. 2026-09-24 14:00 UTCEPSS rescore
  15. 2026-09-24 14:00 UTCEPSS rescore
  16. 2026-09-23 13:44 UTCEPSS rescore
  17. 2026-09-22 14:44 UTCEPSS rescore
  18. 2026-09-21 20:28 UTCEPSS rescore
  19. 2026-09-19 15:37 UTCEPSS rescore
  20. 2026-09-18 19:23 UTCEPSS rescore
  21. 2026-09-18 01:50 UTCOSV refresh
  22. 2026-09-17 19:23 UTCEPSS rescore
  23. 2026-09-16 14:05 UTCEPSS rescore
  24. 2026-09-16 14:04 UTCEPSS rescore
  25. 2026-09-15 03:06 UTCEPSS rescore
Show 75 more
  1. 2026-09-12 14:57 UTCEPSS rescore
  2. 2026-09-11 09:33 UTCEPSS rescore
  3. 2026-09-10 09:29 UTCEPSS rescore
  4. 2026-09-08 21:56 UTCEPSS rescore
  5. 2026-09-06 13:44 UTCEPSS rescore
  6. 2026-09-06 13:44 UTCEPSS rescore
  7. 2026-09-05 15:25 UTCEPSS rescore
  8. 2026-09-04 13:57 UTCEPSS rescore
  9. 2026-09-02 14:08 UTCEPSS rescore
  10. 2026-09-01 13:50 UTCEPSS rescore
  11. 2026-09-01 03:32 UTCEPSS rescore
  12. 2026-08-30 19:14 UTCEPSS rescore
  13. 2026-08-30 02:43 UTCOSV refresh
  14. 2026-08-30 01:19 UTCEPSS rescore
  15. 2026-08-28 21:37 UTCEPSS rescore
  16. 2026-08-26 14:42 UTCEPSS rescore
  17. 2026-08-25 13:45 UTCEPSS rescore
  18. 2026-08-21 23:46 UTCEPSS rescore
  19. 2026-08-20 22:52 UTCEPSS rescore
  20. 2026-08-19 17:01 UTCEPSS rescore
  21. 2026-08-18 13:45 UTCEPSS rescore
  22. 2026-08-17 13:43 UTCEPSS rescore
  23. 2026-08-16 14:52 UTCEPSS rescore
  24. 2026-08-16 02:11 UTCEPSS rescore
  25. 2026-08-15 01:27 UTCEPSS rescore
  26. 2026-08-13 13:51 UTCOSV refresh
  27. 2026-08-12 13:47 UTCEPSS rescore
  28. 2026-08-11 13:38 UTCEPSS rescore
  29. 2026-08-08 16:33 UTCEPSS rescore
  30. 2026-08-07 16:23 UTCEPSS rescore
  31. 2026-08-06 13:43 UTCEPSS rescore
  32. 2026-07-30 16:25 UTCEPSS rescore
  33. 2026-07-30 01:27 UTCEPSS rescore
  34. 2026-07-30 01:27 UTCEPSS rescore
  35. 2026-07-28 20:47 UTCOSV refresh
  36. 2026-07-26 14:52 UTCEPSS rescore
  37. 2026-07-25 14:15 UTCEPSS rescore
  38. 2026-07-24 14:15 UTCEPSS rescore
  39. 2026-07-23 14:15 UTCEPSS rescore
  40. 2026-07-23 01:57 UTCEG score recompute▲ 0.60
  41. 2026-07-22 22:44 UTCEG score recompute
  42. 2026-07-22 14:05 UTCEPSS rescore
  43. 2026-07-21 15:22 UTCEPSS rescore
  44. 2026-07-21 15:22 UTCEPSS rescore
  45. 2026-07-20 17:04 UTCEPSS rescore
  46. 2026-07-19 14:28 UTCEPSS rescore
  47. 2026-07-19 02:26 UTCEPSS rescore
  48. 2026-07-16 17:00 UTCEPSS rescore
  49. 2026-07-15 16:55 UTCEPSS rescore
  50. 2026-07-15 16:55 UTCEPSS rescore
  51. 2026-07-15 01:57 UTCEPSS rescore
  52. 2026-07-13 06:10 UTCEPSS rescore
  53. 2026-07-13 06:10 UTCEPSS rescore
  54. 2026-07-12 05:44 UTCEPSS rescore
  55. 2026-07-12 05:44 UTCEPSS rescore
  56. 2026-07-11 13:22 UTCOSV refresh
  57. 2026-07-11 08:25 UTCEPSS rescore
  58. 2026-07-09 19:07 UTCEPSS rescore
  59. 2026-07-08 15:12 UTCEPSS rescore
  60. 2026-07-04 06:29 UTCEPSS rescore
  61. 2026-07-04 06:29 UTCEPSS rescore
  62. 2026-07-02 16:57 UTCEPSS rescore
  63. 2026-07-01 15:03 UTCEPSS rescore
  64. 2026-06-28 04:54 UTCEPSS rescore
  65. 2026-06-28 04:54 UTCEPSS rescore
  66. 2026-06-27 03:06 UTCEPSS rescore
  67. 2026-06-27 03:06 UTCEPSS rescore
  68. 2026-06-25 13:48 UTCEPSS rescore
  69. 2026-06-25 13:48 UTCEPSS rescore
  70. 2026-06-24 14:03 UTCEPSS rescore
  71. 2026-06-24 14:03 UTCEPSS rescore
  72. 2026-06-23 21:31 UTCEPSS rescore
  73. 2026-06-23 21:31 UTCEPSS rescore
  74. 2026-06-22 19:35 UTCOSV refresh
  75. 2026-06-21 01:58 UTCEPSS rescore

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Frequently asked(5)

What is CVE-2021-23840?
CVE-2021-23840 is a high vulnerability published on February 16, 2021. Calls to EVPCipherUpdate, EVPEncryptUpdate and EVP_DecryptUpdate may overflow the output length argument in some cases where the input length is close to the maximum permissable length for an integer on the platform. In such cases the return value from the function call will be 1 (indicating…
When was CVE-2021-23840 disclosed?
CVE-2021-23840 was first published on February 16, 2021, with the most recent update on April 16, 2026. EchelonGraph re-ingests CVE updates from NVD on a 2-hour cycle, so this page reflects the latest published state.
Is CVE-2021-23840 actively exploited?
CVE-2021-23840 is not currently on CISA's Known Exploited Vulnerabilities catalog. FIRST EPSS estimates a 51% probability of exploitation in the next 30 days (98th percentile of EPSS-scored CVEs).
What is the CVSS score of CVE-2021-23840?
CVE-2021-23840 has a CVSS v3 base score of 7.5 (NVD). EchelonGraph synthesises NVD + CISA KEV + FIRST EPSS + GHSA into a combined EG score of 8.1 (HIGH).
How do I remediate CVE-2021-23840?
A fix for CVE-2021-23840 is available: update to the fixed version the vendor names in its advisory. The vendor advisories EchelonGraph has for CVE-2021-23840 are linked in the Vendor Advisories panel on this page.

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