CVE-2026-58012
Description
A flaw was found in GLib. A buffer over-read can occur in the g_regex_replace function when used with the G_REGEX_RAW compile flag and case-change replacement escapes because the string_append function processes matched substrings using UTF-8 functions that assume valid UTF-8 input, even when the string is treated as raw bytes. This vulnerability can cause a minor information disclosure of 1-5 bytes and a denial of service when the buffer over-read crosses a page boundary.
Statement
Any applications that use g_regex_replace() or g_regex_replace_eval() with the G_REGEX_RAW compile flag and allow user-controlled replacement strings containing case-change escapes (\u, \l, \U, \L) are vulnerable to this issue. This flaw can cause a buffer over-read of 1-5 bytes, leading to a minor information disclosure and a denial of service when the buffer over-read crosses a page boundary. Due to these reasons, this vulnerability has been rated with a moderate severity.
Mitigation
To mitigate this vulnerability, implement strict input validation to sanitize user-supplied replacement strings, specifically rejecting or escaping case-change modifiers (\u, \l, \U, \L) before calling g_regex_replace() or g_regex_replace_eval() when the G_REGEX_RAW compile flag is used. Removing the G_REGEX_RAW flag or hardcoding the replacement strings will completely neutralize this issue.
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 | 6.5 | 8.2 | 6.5 |
| Attack Vector | Network | Network | Network |
| Attack Complexity | Low | Low | Low |
| Privileges Required | None | None | None |
| User Interaction | None | None | None |
| Scope | Unchanged | Unchanged | Unchanged |
| Confidentiality | Low | Low | Low |
| Integrity Impact | None | None | None |
| Availability Impact | Low | High | Low |
Vector
Red Hat: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:N/A:L
NVD: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:N/A:H
cve.org: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:N/A:L
Red Hat CVSS v3 Score Explanation
A denial of service can occur due to an application crash when the buffer over-read crosses an unmapped page boundary. The crash can be reliably reproduced in ASan builds, but not in production environments. To reflect this condition, the availability metric is set to low.
Understanding the Weakness (CWE)
Confidentiality
Technical Impact: Read Memory
Confidentiality
Technical Impact: Bypass Protection Mechanism
By reading out-of-bounds memory, an attacker might be able to get secret values, such as memory addresses, which can bypass protection mechanisms such as ASLR in order to improve the reliability and likelihood of exploiting a separate weakness to achieve code execution instead of just denial of service.
Availability,Integrity
Technical Impact: DoS: Crash, Exit, or Restart
An attacker might be able to cause a crash or other denial of service by causing the product to read a memory location that is not allowed (such as a segmentation fault), or to cause other conditions in which the read operation returns more data than is expected.
Acknowledgements
Red Hat would like to thank linhlhq for reporting this issue.
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