---
title: "CVE-2021-4044: Invalid handling of X509_verify_cert()… | CubePath"
description: "Internally libssl in OpenSSL calls X509_verify_cert() on the client side to verify a certificate supplied by a server. That function may return…"
language: en
source: https://cubepath.com/security/cve/CVE-2021-4044
---

# CVE-2021-4044: Invalid handling of X509_verify_cert()… | CubePath

## Description

Internally libssl in OpenSSL calls X509\_verify\_cert() on the client side to verify a certificate supplied by a server. That function may return a negative return value to indicate an internal error (for example out of memory). Such a negative return value is mishandled by OpenSSL and will cause an IO function (such as SSL\_connect() or SSL\_do\_handshake()) to not indicate success and a subsequent call to SSL\_get\_error() to return the value SSL\_ERROR\_WANT\_RETRY\_VERIFY. This return value is only supposed to be returned by OpenSSL if the application has previously called SSL\_CTX\_set\_cert\_verify\_callback(). Since most applications do not do this the SSL\_ERROR\_WANT\_RETRY\_VERIFY return value from SSL\_get\_error() will be totally unexpected and applications may not behave correctly as a result. The exact behaviour will depend on the application but it could result in crashes, infinite loops or other similar incorrect responses. This issue is made more serious in combination with a separate bug in OpenSSL 3.0 that will cause X509\_verify\_cert() to indicate an internal error when processing a certificate chain. This will occur where a certificate does not include the Subject Alternative Name extension but where a Certificate Authority has enforced name constraints. This issue can occur even with valid chains. By combining the two issues an attacker could induce incorrect, application dependent behaviour. Fixed in OpenSSL 3.0.1 (Affected 3.0.0).

Official description from the CVE record, published by openssl. Copyright © 1999-2026 The MITRE Corporation. See [/security/cve/legal](https://cubepath.com/security/cve/legal) for the CVE license. [View the record on cve.org](https://www.cve.org/CVERecord?id=CVE-2021-4044)

## Key data

### EPSS

Exploit Prediction Scoring System by FIRST: an estimate of the probability that exploitation activity will be observed in the next 30 days.

Score

0.50099 (50.1% probability)

Percentile

98.9%

Scores of

Nov 10, 2026

Model

v2026.06.15

## Affected products

Products listed in the CVE record, as the CNA published them.

- OpenSSL

  - affected: Fixed in OpenSSL 3.0.1 (Affected 3.0.0)

## References

Links listed in the CVE record. They lead to other sites, which CubePath does not control.

- [openssl.org/news/secadv/20211214.txt](https://www.openssl.org/news/secadv/20211214.txt)
- [git.openssl.org/gitweb/?p=openssl.git%3Ba=commitdiff%3Bh=75…](https://git.openssl.org/gitweb/?p=openssl.git%3Ba=commitdiff%3Bh=758754966791c537ea95241438454aa86f91f256)
- [security.netapp.com/advisory/ntap-20211229-0003](https://security.netapp.com/advisory/ntap-20211229-0003/)

## Timeline

1. ID reserved Dec 2, 2021
2. Record published Dec 14, 2021
3. Record last updated Sep 17, 2024

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Data from the CVE Program (MITRE), CISA KEV and FIRST EPSS. CVSS is owned by FIRST and used by permission. Not affiliated with or endorsed by MITRE, CISA or FIRST. Data as of Nov 10, 2026, 20:02 UTC. [Sources and licenses](https://cubepath.com/security/cve/legal)