CVE-2021-37127.4HighCWE-125

CVE-2021-3712: Read buffer overruns processing ASN.1 strings

OpenSSL

Vendor fix available · 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.

48.1%probability of exploitation in the next 30 days

98th percentile

050100

Higher than 98% of scored CVEs

7.4HighCVSS 3.1

LowMediumHighCrit.

DescriptionCVE.org

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).

Affected products1

From the CVE record. A product or version that is not listed is unknown, not unaffected.

OpenSSL · OpenSSLFixed 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)

On the Atlas

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Open the Atlas

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
Weakness: Out-of-bounds Read · Memory Corruption
Vendor: OpenSSL
Published: August 2021
Band: Likely to be exploited (10% or more), August 2021

CoverageNo articles yet

No CyberSIXT article names CVE-2021-3712 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.

References

13 more references are in the CVE record.