A buffer overflow was discovered in libxml2 20904-GITv2.9.4-16-g0741801. The function xmlSnprintfElementContent in valid.c is supposed to recursively dump the element content definition into a char buffer 'buf' of size 'size'. The variable len is assigned strlen(buf). If the content->type is XML_ELEMENT_CONTENT_ELEMENT, then (i) the content->prefix is appended to buf (if it actually fits) whereupon (ii) content->name is written to the buffer. However, the check for whether the content->name actually fits also uses 'len' rather than the updated buffer length strlen(buf). This allows us to write about "size" many bytes beyond the allocated memory. This vulnerability causes programs that use libxml2, such as PHP, to crash.
The MITRE CVE dictionary describes this issue as:
Find out more about CVE-2017-9047 from the MITRE CVE dictionary dictionary and NIST NVD.
This vulnerability exists in the DTD validation functionality of libxml2. Applications that do not attempt to validate untrusted documents are not impacted.
| CVSS3 Base Score | 7.5 |
|---|---|
| CVSS3 Base Metrics | CVSS:3.0/AV:N/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:H |
| Attack Vector | Network |
| Attack Complexity | High |
| Privileges Required | Low |
| User Interaction | None |
| Scope | Unchanged |
| Confidentiality | High |
| Integrity Impact | High |
| Availability Impact | High |
| Platform | Errata | Release Date |
|---|---|---|
| Red Hat JBoss Core Services 1 | RHSA-2018:2486 | 2018-08-16 |
| Platform | Package | State |
|---|---|---|
| Red Hat JBoss Web Server 3.0 | libxml2 | Will not fix |
| Red Hat Enterprise Linux 7 | libxml2 | Will not fix |
| Red Hat Enterprise Linux 6 | libxml2 | Will not fix |
| Red Hat Enterprise Linux 5 | libxml2 | Will not fix |
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