#4838: openssl-1.1.1k (CVE-2021-3450 CVE-2021-3449)
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Reporter: renodr | Owner: lfs-book
Type: task | Status: new
Priority: high | Milestone: 10.2
Component: Book | Version: SVN
Severity: normal | Resolution:
Keywords: |
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Comment (by renodr):
{{{
Changes between 1.1.1j and 1.1.1k [xx XXX xxxx]
Fixed a problem with verifying a certificate chain when using the
X509_V_FLAG_X509_STRICT flag. This flag enables additional security checks
of the certificates present in a certificate chain. It is not set by
default.
Starting from OpenSSL version 1.1.1h a check to disallow certificates
in the chain that have explicitly encoded elliptic curve parameters was
added as an additional strict check.
An error in the implementation of this check meant that the result of
a previous check to confirm that certificates in the chain are valid CA
certificates was overwritten. This effectively bypasses the check that
non-CA certificates must not be able to issue other certificates.
If a "purpose" has been configured then there is a subsequent
opportunity for checks that the certificate is a valid CA. All of the
named "purpose" values implemented in libcrypto perform this check.
Therefore, where a purpose is set the certificate chain will still be
rejected even when the strict flag has been used. A purpose is set by
default in libssl client and server certificate verification routines, but
it can be overridden or removed by an application.
In order to be affected, an application must explicitly set the
X509_V_FLAG_X509_STRICT verification flag and either not set a purpose for
the certificate verification or, in the case of TLS client or server
applications, override the default purpose. ([CVE-2021-3450])
Tomáš Mráz
Fixed an issue where 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. ([CVE-2021-3449])
Peter Kästle and Samuel Sapalski
}}}
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