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Published: 24 August 2021

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).


in 1.0.2, this bug is in X509_CERT_AUX_print()
list of commits below is incomplete



Cvss 3 Severity Score


Score breakdown


Package Release Status
Launchpad, Ubuntu, Debian
bionic Needs triage

Released (0~20191122.bd85bf54-2ubuntu3.3)
Released (2020.11-4ubuntu0.1)
impish Ignored
(reached end-of-life)
jammy Needs triage

kinetic Needs triage

trusty Does not exist

upstream Needs triage

xenial Needs triage

Launchpad, Ubuntu, Debian
bionic Not vulnerable
(uses system openssl1.0)
focal Not vulnerable
(uses system openssl1.1)
hirsute Not vulnerable
(uses system openssl1.1)
impish Not vulnerable
(uses system openssl1.1)
jammy Needed

kinetic Not vulnerable
(uses system openssl1.1)
trusty Not vulnerable
(uses system openssl)
upstream Needs triage

xenial Not vulnerable
(uses system openssl)
Launchpad, Ubuntu, Debian
Released (1.1.1-1ubuntu2.1~18.04.13)
Released (1.1.1f-1ubuntu2.8)
Released (1.1.1j-1ubuntu3.5)
Released (1.1.1l-1ubuntu1)
Released (1.1.1l-1ubuntu1)
Released (1.1.1l-1ubuntu1)
Released (1.0.1f-1ubuntu2.27+esm4)
upstream Needs triage

Released (1.0.2g-1ubuntu4.20+esm1)
Launchpad, Ubuntu, Debian
Released (1.0.2n-1ubuntu5.7)
focal Does not exist

hirsute Does not exist

impish Does not exist

jammy Does not exist

kinetic Does not exist

trusty Does not exist

upstream Needs triage

xenial Does not exist

Severity score breakdown

Parameter Value
Base score 7.4
Attack vector Network
Attack complexity High
Privileges required None
User interaction None
Scope Unchanged
Confidentiality High
Integrity impact None
Availability impact High
Vector CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:N/A:H