CVE-2021-3449

MEDIUMNVD 5.95.9—
EchelonGraph scoreMEDIUM confidence

This medium-severity CVE scores 5.9 under NVD CVSS v3. EPSS exploit probability: 9.9%, top 7% 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
Elevated
5.9
EchelonGraph verdictPatch this weekExploitation is likely or a public exploit exists.
  • High exploitation likelihood — EPSS 63%
CISA-KEV: Not listedEPSS: 63%CVSS: 5.9Exploit: NoneExposed: 0

A fix is available — apply it.

An OpenSSL TLS server may crash if sent a maliciously crafted renegotiation ClientHello message from a client. If a TLSv1.2 renegotiation ClientHello omits the signature_algorithms extension (where it was present in the initial ClientHello), but includes a signature_algorithms_cert extension then a NULL pointer dereference will result, leading to a crash and a denial of service attack. A server is only vulnerable if it has TLSv1.2 and renegotiation enabled (which is the default configuration). OpenSSL TLS clients are not impacted by this issue. All OpenSSL 1.1.1 versions are affected by this issue. Users of these versions should upgrade to OpenSSL 1.1.1k. OpenSSL 1.0.2 is not impacted by this issue. Fixed in OpenSSL 1.1.1k (Affected 1.1.1-1.1.1j).

CVSS v3
5.9
EG Score
5.9(medium)
EPSS
99.1%
KEV
Not listed

Published

March 25, 2021

Last Modified

November 21, 2024

References (58)

Patch Availability(11)

Vendor / EcosystemFixed in / PatchReleasedSource
ubuntuopenssl (1.1.1f-1ubuntu2.3) @ focal2026-05-26ubuntu
ubuntulibecpg-compat3 (12.8-0ubuntu0.20.04.1) @ focal2026-05-26ubuntu
redhatjws5-tomcat-native-0:1.2.25-4.redhat_4.el8jws2021-04-14redhat
redhatopenssl2021-04-14redhat
redhattomcat-native-0:1.2.23-24.redhat_24.ep7.el72021-04-14redhat
redhatpatch2021-04-14redhat
redhatredhat-virtualization-host-0:4.4.5-20210330.0.el8_32021-04-14redhat
redhatjbcs-httpd24-openssl-pkcs11-0:0.4.10-20.jbcs.el72021-04-14redhat
redhatopenssl-1:1.1.1c-5.el8_12021-04-07redhat
redhatopenssl-1:1.1.1c-18.el8_22021-04-05redhat
redhatopenssl-1:1.1.1g-15.el8_32021-03-30redhat

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—111.15.0—

Weakness Classification(1)

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

All Vendor Advisories

(13)

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

Publicly available exploits

(1 reference)

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

  • GitHub PoCriptl/cve-2021-3449
    First seen Mar 26, 2021

    CVE-2021-3449 OpenSSL denial-of-service exploit 👨🏻‍💻

    Open source ↗

Frequently asked(5)

What is CVE-2021-3449?
CVE-2021-3449 is a medium vulnerability published on March 25, 2021. An OpenSSL TLS server may crash if sent a maliciously crafted renegotiation ClientHello message from a client. If a TLSv1.2 renegotiation ClientHello omits the signaturealgorithms extension (where it was present in the initial ClientHello), but includes a signaturealgorithms_cert extension then a…
When was CVE-2021-3449 disclosed?
CVE-2021-3449 was first published in the National Vulnerability Database on March 25, 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-2021-3449 actively exploited?
CVE-2021-3449 is not currently on CISA's Known Exploited Vulnerabilities catalog. FIRST EPSS estimates a 99.1% percentile likelihood of exploitation in the next 30 days — higher percentiles indicate greater predicted risk.
What is the CVSS score of CVE-2021-3449?
CVE-2021-3449 has a CVSS v3 base score of 5.9 (NVD).
How do I remediate CVE-2021-3449?
Patch to the fixed version published by the affected vendor. Where vendor advisories exist for CVE-2021-3449, 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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