In this deep-dive, we will closely examine a vulnerability identified as CVE-2018-9383 that originates from an oversight in the implementation of the asn1_ber_decoder function located in asn1_decoder.c. We will cover the specifics of the vulnerability, showcase a relevant code snippet that demonstrates the issue, and provide links to original references. This vulnerability is associated with the possibility of an out-of-bounds read, which, if exploited successfully, could result in local information disclosure. System execution privileges are required for a potential attacker, and user interaction is not necessary.
Code Snippet
The root cause of the vulnerability can be traced back to a missing bounds check in the implementation of the asn1_ber_decoder function. Here is the code snippet that highlights the issue:
int asn1_ber_decoder(const asn1_node_st *functions,
void *mem_pool,
const unsigned char *ider,
const unsigned char *in, long len,
asn1_node *element)
{
long tag_len, elem_len;
asn1_node_st etmp;
while (1)
{
if (len == )
return ERR_ASN1_OUT_OF_DATA;
/* Check for end of constructed element */
if ((in[] == ) && (in[1] == ))
{
in += 2;
len -= 2;
return ERR_ASN1_ELEMENT_NOT_FOUND;
}
/* Should always be 2 */
tag_len = asn1_get_tag(in, len, &etmp.s_tag, &etmp.s_class, &elem_len);
...
}
}
Exploit Details
The specific flaw lies in the absence of a bounds check on the 'in' pointer utilized in this particular block of code:
if ((in[] == ) && (in[1] == ))
This missing bounds check may allow an attacker to perform an out-of-bounds read, leading to a potential information disclosure. One critical aspect of this vulnerability is that it does not necessitate user interaction, which significantly increases its impact. However, the attacker needs to have system execution privileges for the successful exploitation of this flaw, which mitigates the severity to some extent.
Original References
For further information and an in-depth exploration of the CVE-2018-9383 vulnerability, you can refer to the original resources listed below:
1. NVD - CVE-2018-9383
2. oss-security - CVE-2018-9383
3. Android Security Bulletin - August 2018
Conclusion
The CVE-2018-9383 vulnerability highlights the importance of proper bounds checking and its potential repercussions when overlooked. Although this specific vulnerability requires system execution privileges and does not necessitate user interaction, its discovery and disclosure underscore the vital role of responsible vulnerability handling and software development practices. By examining these flaws, developers can learn valuable lessons to enhance their future code quality and better protect users from malicious exploitation.
Timeline
Published on: 01/17/2025 23:15:12 UTC
Last modified on: 01/21/2025 17:15:12 UTC