# CVE-2026-58012: GNOME GLib buffer over-read in g_regex_replace

Source: https://junglewise.ai/threats/cve-2026-58012-gnome-glib-buffer-over-read-in-g-regex-replace  
Publisher: Junglewise Threat Intelligence, https://junglewise.ai/threats  
Published: 2026-06-30. Updated: 2026-06-30  
License: CC BY 4.0 with a link back

CVE-2026-58012 · Severity: medium · CVSS 6.5 · Published 2026-06-30

GLib is a fundamental software library used by many Linux applications to handle core data structures and utilities. A flaw in its regular expression processing allows an attacker to trigger a memory error when the library processes specially crafted text. This can lead to a program crash (denial of service) or the accidental exposure of small amounts of sensitive information from the computer's memory.

Technologies: [Gnome Glib](https://junglewise.ai/threats/technologies/glib). Vendors: [Gnome](https://junglewise.ai/threats/vendors/gnome).

## Quick answers

**Is CVE-2026-58012 exploited in the wild?** No. Junglewise Threat Intelligence has no report of CVE-2026-58012 being exploited in the wild.

**How severe is CVE-2026-58012?** Medium severity, with a CVSS score of 6.5, published 30 June 2026.

**Which products and versions are affected?** Gnome Glib All versions since introduction of G_REGEX_RAW with case-change replacement escapes.

**Is there a fix for CVE-2026-58012?** No fixed version is recorded yet. Check the vendor's advisory in the references below. If you run it, Junglewise drafts a mitigation that fits your setup and applies it once you approve, with senior security engineers behind it.

**How is CVE-2026-58012 attacked?** It is attacked over the network, in a software library.

**Am I affected by CVE-2026-58012?** Check whether you run Gnome Glib at an affected version. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.

## Technical details

A heap-buffer-overflow READ vulnerability exists in GLib's g_regex_replace() function. When the G_REGEX_RAW flag is used, the underlying PCRE2 engine treats strings as raw bytes, which may include invalid UTF-8 sequences. However, if the replacement string contains case-change escapes (such as \U, \L, \u, or \l), the internal string_append() function incorrectly uses UTF-8 functions (g_utf8_get_char and g_utf8_next_char) to process these bytes. If a byte indicates a multi-byte UTF-8 sequence that exceeds the actual allocated buffer size, the library reads 1-5 bytes out-of-bounds. This can result in a crash if the read crosses a page boundary or if AddressSanitizer is active, and it can leak adjacent heap memory into the resulting output string.

## Affected products

- GNOME GLib All versions since introduction of G_REGEX_RAW with case-change replacement escapes
- Red Hat Red Hat Enterprise Linux 6
- Red Hat Red Hat Enterprise Linux 7
- Red Hat Red Hat Enterprise Linux 8
- Red Hat Red Hat Enterprise Linux 9
- Red Hat Red Hat Enterprise Linux 10

## Timeline

- 2026-01-30: disclosed: Reported via YesWeHack
- 2026-06-24: other: Bug reported to Red Hat Bugzilla
- 2026-06-30: advisory: CVE published by Red Hat

## References

- [https://access.redhat.com/downloads/content/package-browser/](https://access.redhat.com/downloads/content/package-browser/)
- [https://access.redhat.com/security/cve/CVE-2026-58012](https://access.redhat.com/security/cve/CVE-2026-58012)
- [https://bugzilla.redhat.com/show_bug.cgi?id=2492247](https://bugzilla.redhat.com/show_bug.cgi?id=2492247)
- [https://gitlab.gnome.org/GNOME/glib/-/issues/3918](https://gitlab.gnome.org/GNOME/glib/-/issues/3918)

## Related threats

- [GNOME GLib denial of service in GDBus authentication](https://junglewise.ai/threats/cve-2026-15588-gnome-glib-denial-of-service-in-gdbus-authentication)
- [GNOME GLib out-of-bounds read in D-Bus introspection XML parsing](https://junglewise.ai/threats/cve-2026-58016-gnome-glib-out-of-bounds-read-in-d-bus-introspection-xml-parsing)
- [GLib path traversal in GDBus DBUS_COOKIE_SHA1 authentication](https://junglewise.ai/threats/cve-2026-58015-glib-path-traversal-in-gdbus-dbus-cookie-sha1-authentication)
- [GNOME GLib off-by-one error in g_key_file_get_locale_string_list](https://junglewise.ai/threats/cve-2026-58014-gnome-glib-off-by-one-error-in-g-key-file-get-locale-string-list)
- [GNOME GLib buffer over-read in g_io_channel_read_line_backend](https://junglewise.ai/threats/cve-2026-58013-gnome-glib-buffer-over-read-in-g-io-channel-read-line-backend)