CVE-2024-2961
Description
An out-of-bounds write flaw was found in the ISO-2022-CN-EXT plugin for glibc's iconv library. When converting from UCS4 charset, adding certain escape charterers is required to indicate where the charset was changed to the library. During this process, iconv improperly checks the boundaries of internal buffers, leading to a buffer overflow, which allows writing up to 3 bytes outside the desired memory location. This issue may allow an attacker to craft a malicious characters sequence that will trigger the out-of-bounds write and perform remote code execution, presenting a high impact to the Integrity, Confidentiality, and Availability triad.
Statement
The described vulnerability in the iconv() function of GNU C Library, particularly affecting ISO-2022-CN-EXT character set conversions, poses a important severity issue due to its potential for out-of-bound writes. Such buffer overflows can lead to arbitrary memory corruption, which can be exploited by attackers to execute arbitrary code, crash applications, or overwrite critical data structures, including neighboring variables. Given that the overflow can occur with specific, predictable values through SS2designation and SS3designation escape sequences, an attacker could craft malicious input to specifically trigger these overflows. Exploitation of this vulnerability could result in denial of service, privilege escalation, or even remote code execution, posing a significant threat to the security and integrity of affected systems.
Mitigation
This issue can be mitigated by removing the ISO-2022-CN-EXT from glibc-gconv-extra's modules configuration. This can be done by:
1) Verify if the module is loaded by running:
$ iconv -l | grep -E 'CN-?EXT'
ISO-2022-CN-EXT//
ISO2022CNEXT//
If the grep output looks like the above, ISO-2022-CN-EXT module is enabled.
2) Disabled the module by editing the file located at /usr/lib64/gconv/gconv-modules.d/gconv-modules-extra.conf and comment the following lines. For RHEL 7 the file that needs to be edited is /usr/lib64/gconv/gconv-modules. This step requires to be executed by a privileged user:
# from to module cost
alias ISO2022CNEXT// ISO-2022-CN-EXT//
module ISO-2022-CN-EXT// INTERNAL ISO-2022-CN-EXT 1
module INTERNAL ISO-2022-CN-EXT// ISO-2022-CN-EXT 1
For commenting those lines just add the '#' character at the beginning of mentioned lines:
# from to module cost
#alias ISO2022CNEXT// ISO-2022-CN-EXT//
#module ISO-2022-CN-EXT// INTERNAL ISO-2022-CN-EXT 1
#module INTERNAL ISO-2022-CN-EXT// ISO-2022-CN-EXT 1
3) Update the iconv cache by running:
sudo iconvconfig
4) Check if the module was disabled by running the first step again. This time ISO-2022-CN-EXT should not appear in the output.
Please notice that disabling the mentioned gconv module may lead applications relying in the affected module to fail in converting characters and should be used as a temporary mitigation before being able to fully update the affected package.
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 | 8.8 | N/A | 7.3 |
| Attack Vector | Network | N/A | Local |
| Attack Complexity | Low | N/A | Low |
| Privileges Required | Low | N/A | None |
| User Interaction | None | N/A | None |
| Scope | Unchanged | N/A | Unchanged |
| Confidentiality | High | N/A | Low |
| Integrity Impact | High | N/A | Low |
| Availability Impact | High | N/A | High |
Vector
Red Hat: CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
cve.org: CVSS:3.1/AV:L/AC:L/PR:N/UI:N/S:U/C:L/I:L/A:H
Understanding the Weakness (CWE)
Integrity
Technical Impact: Modify Memory; Execute Unauthorized Code or Commands
Write operations could cause memory corruption. In some cases, an adversary can modify control data such as return addresses in order to execute unexpected code.
Availability
Technical Impact: DoS: Crash, Exit, or Restart
Attempting to access out-of-range, invalid, or unauthorized memory could cause the product to crash.
Other
Technical Impact: Unexpected State
Subsequent write operations can produce undefined or unexpected results.
Acknowledgements
Red Hat would like to thank Charles Fol for reporting this issue.
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