CVE-2021-4044: Invalid handling of X509_verify_cert() internal errors in libssl
Affected: OpenSSL · Exploitation: likely to be exploited (10% or more)
Not in CyberSIXT coverage yet: no article names this CVE. This page shows the public record.
Higher than 98% of scored CVEs
Not scored yet. The CVE record carries no CVSS score.
DescriptionCVE.org
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).
Affected products1
From the CVE record. A product or version that is not listed is unknown, not unaffected.
- OpenSSL · OpenSSLFixed in OpenSSL 3.0.1 (Affected 3.0.0)
On the Atlas
Every published CVE is on the CyberSIXT Atlas, grouped by weakness, vendor and month.
- Exploitation
- Likely to be exploited (10% or more). EPSS gives it a 10% or higher chance of exploitation in the next 30 days.
- CISA KEV
- Not listed
- Public check
- No public nuclei template
- Vendor
- OpenSSL
- Published
- December 2021
CoverageNo articles yet
No CyberSIXT article names CVE-2021-4044 yet, so there is no coverage timeline, action brief or change log for it. Everything on this page comes from the public CVE record, CISA KEV, EPSS and the nuclei template index. Search the archive or see the CVEs in the news.