CVE-2018-18751
Description
From CVE.org
An issue was discovered in GNU gettext 0.19.8. There is a double free in default_add_message in read-catalog.c, related to an invalid free in po_gram_parse in po-gram-gen.y, as demonstrated by lt-msgfmt.
Statement
This issue affects the versions of gettext as shipped with Red Hat Enterprise Linux 7.
This issue did not affect the versions of gettext as shipped with Red Hat Enterprise Linux 5 and 6.
Common Vulnerability Scoring System (CVSS) Score Details
Info alert:Important note
CVSS scores for open source components depend on vendor-specific factors (e.g. version or build chain). Therefore, Red Hat's score and impact rating can be different from NVD and other vendors. Red Hat remains the authoritative CVE Naming Authority (CNA) source for its products and services (see Red Hat classifications).
CVSS v3 Score Breakdown
| Red Hat | NVD | cve.org | |
|---|---|---|---|
| Base Score | 4 | 9.8 | N/A |
| Attack Vector | Local | Network | N/A |
| Attack Complexity | Low | Low | N/A |
| Privileges Required | None | None | N/A |
| User Interaction | None | None | N/A |
| Scope | Unchanged | Unchanged | N/A |
| Confidentiality | None | High | N/A |
| Integrity Impact | None | High | N/A |
| Availability Impact | Low | High | N/A |
Vector
Red Hat: CVSS:3.0/AV:L/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L
NVD: CVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
Red Hat CVSS v3 Score Explanation
The access vector has been set to local, as gettext is not bound to the network stack and usually operates on local files. Considering how this tool is generally used, combined with the mitigations Red Hat Enterprise Linux provides, the most likely impact would be a mere crash and the availability impact has been set to low. It's worth adding that translation files should come from a trusted source, otherwise the correct operation/translation of an application using gettext can't be guaranteed and could even introduce problems more severe than the vulnerability described here.
Understanding the Weakness (CWE)
Integrity
Technical Impact: Modify Memory
The use of previously freed memory may corrupt valid data, if the memory area in question has been allocated and used properly elsewhere.
Availability
Technical Impact: DoS: Crash, Exit, or Restart
If chunk consolidation occurs after the use of previously freed data, the process may crash when invalid data is used as chunk information.
Confidentiality
Technical Impact: Read Memory
Read operations on freed memory can sometimes leak sensitive information instead of causing a crash
Integrity,Confidentiality,Availability
Technical Impact: Execute Unauthorized Code or Commands
If malicious data is entered before chunk consolidation can take place, it may be possible to take advantage of a write-what-where primitive to execute arbitrary code. If the newly allocated data happens to hold a class, in C++ for example, various function pointers may be scattered within the heap data. If one of these function pointers is overwritten with an address to valid shellcode, execution of arbitrary code can be achieved.
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