cbcvebase.
CVE-2021-3712
published 2021-08-24

CVE-2021-3712: 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…

PriorityP262high7.4CVSS 3.1
AVNACHPRNUINSUCHINAH
EPSS
50.44%
98.8th percentile
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

Affected

69 ranges· showing 25
VendorProductVersion rangeFixed in
debiandebian_linux
debiandebian_linux
debiandebian_linux
debianopenssl< openssl 1.1.1l-1 (bookworm)openssl 1.1.1l-1 (bookworm)
mcafeeepolicy_orchestrator< 5.10.05.10.0
mcafeeepolicy_orchestrator
msrcazl3_edk2_20230301gitf80f052277c8-37_on_azure_linux_3.0
msrcazl3_edk2_20240223gitedc6681206c1-1_on_azure_linux_3.0
msrcazl3_shim-unsigned-aarch64_15.8-5_on_azure_linux_3.0
msrcazure_linux_3.0_arm
msrcazure_linux_3.0_x64
msrccbl2_openssl_1.1.1k-11_on_cbl_mariner_2.0
msrccbl_mariner_1.0_arm
msrccbl_mariner_1.0_x64
msrccbl_mariner_2.0_arm
msrccbl_mariner_2.0_x64
msrccm1_openssl_1.1.1k-8_on_cbl_mariner_1.0
netappe-series_santricity_os_controller11.0 – 11.50.2
opensslopenssl
opensslopenssl
opensslopenssl>= 0 < 1.1.1k-1+deb11u11.1.1k-1+deb11u1
opensslopenssl>= 0 < 1.1.1l-11.1.1l-1
opensslopenssl>= 0 < 1.1.1l-11.1.1l-1
opensslopenssl>= 0 < 1.1.1l-11.1.1l-1
opensslopenssl>= 0 < 1.1.1-1ubuntu2.1~18.04.131.1.1-1ubuntu2.1~18.04.13

Detection & IOCsextracted from sources · hover to see the quote

  • Trigger condition: application directly constructs ASN1_STRING structures without NUL-terminating the 'data' field (e.g., by directly setting 'data' and 'length' fields or using ASN1_STRING_set0()), then passes them through OpenSSL print or name-constraints processing functions — this causes a read buffer overrun
  • Monitor calls to X509_get1_email(), X509_REQ_get1_email(), and X509_get1_ocsp() with certificates containing non-NUL-terminated ASN1_STRING fields as these are confirmed vulnerable code paths
  • Watch for exploitation via name constraints processing in certificate handling — specially crafted certificates with non-NUL-terminated ASN1_STRING structures in name constraints fields can trigger the overread
  • Outcome of successful exploitation includes crash (DoS) or disclosure of private memory contents such as private keys or sensitive plaintext — monitor for unexpected OpenSSL process crashes or anomalous memory reads following certificate/ASN.1 processing
  • ·Affected OpenSSL versions are 1.1.1 through 1.1.1k (fixed in 1.1.1l) and 1.0.2 through 1.0.2y (fixed in 1.0.2za); detection rules and scanning should target these version ranges
  • ·The vulnerability requires the application to directly construct ASN1_STRING without using OpenSSL's own d2i parsing functions or ASN1_STRING_set(); strings parsed via standard OpenSSL APIs are NUL-terminated and not directly vulnerable
  • ·No known public exploits specifically targeting this vulnerability were identified at time of ICS advisory publication

CVSS provenance

nvdv3.17.4HIGHCVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:N/A:H
nvdv2.05.8MEDIUMAV:N/AC:M/Au:N/C:P/I:N/A:P
osv9.8CRITICAL
vendor_ubuntu9.8CRITICAL
vendor_debian7.4HIGH
vendor_msrc7.4HIGH
vendor_oracle7.4HIGH
vendor_redhat7.4HIGH
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