CVE-2021-23841

MEDIUMNVD 5.95.9—
EchelonGraph scoreMEDIUM confidence

This medium-severity CVE scores 5.9 under NVD CVSS v3. EPSS exploit probability: 1.0%, top 23% of all CVEs by exploit prediction. GitHub Security Advisory data not yet ingested — confidence will rise once GHSA publishes (typical lag: hours to days for open-source ecosystem CVEs; never for infrastructure-only CVEs).

Triggered by: NVD CVSS baseline
Sources: epss, nvd
5.9
EchelonGraph verdictMonitorLow exploitation likelihood right now — keep watching.
  • Lower severity and no public exploit yet
CISA-KEV: Not listedEPSS: 7%CVSS: 5.9Exploit: NoneExposed: 0

A fix is available — apply it.

The OpenSSL public API function X509_issuer_and_serial_hash() attempts to create a unique hash value based on the issuer and serial number data contained within an X509 certificate. However it fails to correctly handle any errors that may occur while parsing the issuer field (which might occur if the issuer field is maliciously constructed). This may subsequently result in a NULL pointer deref and a crash leading to a potential denial of service attack. The function X509_issuer_and_serial_hash() is never directly called by OpenSSL itself so applications are only vulnerable if they use this function directly and they use it on certificates that may have been obtained from untrusted sources. 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
5.9
EG Score
5.9(medium)
EPSS
93.7%
KEV
Not listed

Published

February 16, 2021

Last Modified

November 21, 2024

References (44)

Vendor Advisories for CVE-2021-23841(4)

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

Patch Availability(9)

Vendor / EcosystemFixed in / PatchReleasedSource
ubuntuopenssl1.0 (1.0.2n-1ubuntu5.6) @ bionic2026-05-26ubuntu
ubuntulibssl1.0.0-udeb (1.0.1f-1ubuntu2.27+esm2) @ trusty2026-05-26ubuntu
redhatpatch2021-11-30redhat
redhatjws5-tomcat-vault-0:1.1.8-4.Final_redhat_00004.1.el8jws2021-11-30redhat
redhatjbcs-httpd24-openssl2021-11-10redhat
redhatjbcs-httpd24-openssl-pkcs11-0:0.4.10-22.jbcs.el72021-11-10redhat
redhatedk2-0:20210527gite1999b264f1f-3.el82021-11-09redhat
redhatopenssl-1:1.1.1k-4.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

(1 across 1 ecosystem)
crates.io(1)
PackageVulnerable rangeFixed inDependents
openssl-src—111.14.0—

Weakness Classification(1)

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

Additional Vendor Advisories

(7)

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

Frequently asked(5)

What is CVE-2021-23841?
CVE-2021-23841 is a medium vulnerability published on February 16, 2021. The OpenSSL public API function X509issuerandserialhash() attempts to create a unique hash value based on the issuer and serial number data contained within an X509 certificate. However it fails to correctly handle any errors that may occur while parsing the issuer field (which might occur if the…
When was CVE-2021-23841 disclosed?
CVE-2021-23841 was first published in the National Vulnerability Database on February 16, 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-2021-23841 actively exploited?
CVE-2021-23841 is not currently on CISA's Known Exploited Vulnerabilities catalog. FIRST EPSS estimates a 93.7% percentile likelihood of exploitation in the next 30 days — higher percentiles indicate greater predicted risk.
What is the CVSS score of CVE-2021-23841?
CVE-2021-23841 has a CVSS v3 base score of 5.9 (NVD).
How do I remediate CVE-2021-23841?
Patch to the fixed version published by the affected vendor. Where vendor advisories exist for CVE-2021-23841, 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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