CVE-2021-3712 - Out-of-bounds Read

Severity

74%

Complexity

22%

Confidentiality

86%

ASN.1 strings are represented internally within OpenSSL as an ASN1_STRING structure which contains a buffer holding the string data and a field holding the buffer length. This contrasts with normal C strings which are repesented as a buffer for the string data which is terminated with a NUL (0) byte. Although not a strict requirement, ASN.1 strings that are parsed using OpenSSL's own "d2i" functions (and other similar parsing functions) as well as any string whose value has been set with the ASN1_STRING_set() function will additionally NUL terminate the byte array in the ASN1_STRING structure. However, it is possible for applications to directly construct valid ASN1_STRING structures which do not NUL terminate the byte array by directly setting the "data" and "length" fields in the ASN1_STRING array. This can also happen by using the ASN1_STRING_set0() function. Numerous OpenSSL functions that print ASN.1 data have been found to assume that the ASN1_STRING byte array will be NUL terminated, even though this is not guaranteed for strings that have been directly constructed. Where an application requests an ASN.1 structure to be printed, and where that ASN.1 structure contains ASN1_STRINGs that have been directly constructed by the application without NUL terminating the "data" field, then a read buffer overrun can occur. The same thing can also occur during name constraints processing of certificates (for example if a certificate has been directly constructed by the application instead of loading it via the OpenSSL parsing functions, and the certificate contains non NUL terminated ASN1_STRING structures). It can also occur in the X509_get1_email(), X509_REQ_get1_email() and X509_get1_ocsp() functions. If a malicious actor can cause an application to directly construct an ASN1_STRING and then process it through one of the affected OpenSSL functions then this issue could be hit. This might result in a crash (causing a Denial of Service attack). It could also result in the disclosure of private memory contents (such as private keys, or sensitive plaintext). Fixed in OpenSSL 1.1.1l (Affected 1.1.1-1.1.1k). Fixed in OpenSSL 1.0.2za (Affected 1.0.2-1.0.2y).

CVSS 3.1 Base Score 7.4. CVSS Attack Vector: network. CVSS Attack Complexity: high. CVSS Vector: (CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:N/A:H).

CVSS 2.0 Base Score 5.8. CVSS Attack Vector: network. CVSS Attack Complexity: medium. CVSS Vector: (AV:N/AC:M/Au:N/C:P/I:N/A:P).

Demo Examples

Out-of-bounds Read

CWE-125

In the following code, the method retrieves a value from an array at a specific array index location that is given as an input parameter to the method


               
}
return value;// check that the array index is less than the maximum// length of the array
value = array[index];// get the value at the specified index of the array
// if array index is invalid then output error message// and return value indicating error
value = -1;

However, this method only verifies that the given array index is less than the maximum length of the array but does not check for the minimum value (CWE-839). This will allow a negative value to be accepted as the input array index, which will result in a out of bounds read (CWE-125) and may allow access to sensitive memory. The input array index should be checked to verify that is within the maximum and minimum range required for the array (CWE-129). In this example the if statement should be modified to include a minimum range check, as shown below.


               
...// check that the array index is within the correct// range of values for the array

Overview

First reported 2 months ago

2021-08-24 15:15:00

Last updated 3 days ago

2021-10-22 08:15:00

Affected Software

OpenSSL Project OpenSSL

NetApp E-Series SANtricity OS Controller

References

https://www.openssl.org/news/secadv/20210824.txt

https://git.openssl.org/gitweb/?p=openssl.git;a=commitdiff;h=94d23fcff9b2a7a8368dfe52214d5c2569882c11

https://git.openssl.org/gitweb/?p=openssl.git;a=commitdiff;h=ccb0a11145ee72b042d10593a64eaf9e8a55ec12

DSA-4963

[tomcat-dev] 20210825 OpenSSL security announcement - do we need a Tomcat Native release?

[oss-security] 20210825 OpenSSL SM2 Decryption Buffer Overflow (CVE-2021-3711), Read buffer overruns processing ASN.1 strings (CVE-2021-3712)

[tomcat-dev] 20210826 Re: OpenSSL security announcement - do we need a Tomcat Native release?

https://security.netapp.com/advisory/ntap-20210827-0010/

https://www.openssl.org/news/secadv/20210824.txt

Vendor Advisory

https://git.openssl.org/gitweb/?p=openssl.git;a=commitdiff;h=94d23fcff9b2a7a8368dfe52214d5c2569882c11

Mailing List, Patch, Vendor Advisory

https://git.openssl.org/gitweb/?p=openssl.git;a=commitdiff;h=ccb0a11145ee72b042d10593a64eaf9e8a55ec12

Mailing List, Patch, Vendor Advisory

DSA-4963

Third Party Advisory

[tomcat-dev] 20210825 OpenSSL security announcement - do we need a Tomcat Native release?

Mailing List, Third Party Advisory

[oss-security] 20210825 OpenSSL SM2 Decryption Buffer Overflow (CVE-2021-3711), Read buffer overruns processing ASN.1 strings (CVE-2021-3712)

Mailing List, Third Party Advisory

[tomcat-dev] 20210826 Re: OpenSSL security announcement - do we need a Tomcat Native release?

Mailing List, Third Party Advisory

https://security.netapp.com/advisory/ntap-20210827-0010/

Third Party Advisory

https://www.tenable.com/security/tns-2021-16

[debian-lts-announce] 20210926 [SECURITY] [DLA 2766-1] openssl security update

[debian-lts-announce] 20210930 [SECURITY] [DLA 2774-1] openssl1.0 security update

https://www.oracle.com/security-alerts/cpuoct2021.html

https://kc.mcafee.com/corporate/index?page=content&id=SB10366

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