CVE-2025-4373 | Glib: buffer underflow on glib through glib/gstring.c via function g_string_insert_unichar

A flaw was found in GLib, which is vulnerable to an integer overflow in the g_string_insert_unichar() function. When the position at which to insert the character is large, the position will overflow, leading to a buffer underwrite.

Published: 2025-05-06 Last update: 2026-05-12 Assigner: [email protected] Source: [email protected]

Conclusion & alert: CVE-2025-4373 is rated Moderate Risk (44.8/100): CVSS Medium severity, with medium exploitation likelihood (EPSS 0.74%). Mandatory action: Review affected assets and schedule remediation.

Risk is dynamic; we continuously reassess and refresh what is shown on this page as upstream context changes.

Exploit prediction scoring system (EPSS) score for CVE-2025-4373

EPSS lead: Daily EPSS estimates relative likelihood of exploitation; percentile ranks this CVE among scored vulnerabilities (higher = more severe relative rank).

# Date Old EPSS score New EPSS score Delta (New - Old)
1 2026-04-23 0.76% 0.74% -0.01%
2 2026-04-21 0.74% 0.76% +0.01%
3 2026-03-02 0.74%

Full EPSS history (10 records total)

Common vulnerability scoring system (CVSS) metrics for CVE-2025-4373

CVSS metrics for this CVE.

Base score Version Severity Vector Exploitability Impact Score source
4.8 3.1 MEDIUM
CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:L/A:L Click to expand
Attack vector (AV:N)
Could be attacked over the internet or any normal routed network—not just someone sitting at the machine.
Attack complexity (AC:H)
Even with access, the exploit needs extra luck, timing, or a fussy environment to actually work.
Privileges required (PR:N)
No account or special rights needed—anonymous or random user is enough.
User interaction (UI:N)
Nobody has to click “OK” or open a trap file; it can work without a victim helping.
Scope (S:U)
Damage stays in the same “trust bubble” as the broken component—no big spill into unrelated systems.
Confidentiality (C:N)
Doesn’t really leak secrets in a meaningful way.
Integrity (I:L)
Attackers could change some data, but it’s limited—not everything goes.
Availability (A:L)
Might cause slowdowns, glitches, or partial disruption—not a full brick.
2.2 2.5 [email protected]

Weakness enumeration for CVE-2025-4373

GitHub Security Advisory for CVE-2025-4373

GHSA-cfv9-2rgf-f55c · Severity: medium — A flaw was found in GLib, which is vulnerable to an integer overflow in the...

OS Trackers for CVE-2025-4373

vendor priority summary link
debian not yet assigned CVE-2025-4373 not yet assigned priority: Debian including 1 source packages (glib2.0), 5 status rows across 5 suites (bookworm, bullseye, forky, sid, trixie): resolved 5. https://security-tracker.debian.org/tracker/CVE-2025-4373
redhat medium https://access.redhat.com/security/cve/CVE-2025-4373
suse medium CVE-2025-4373 severity moderate: SUSE including 466 source package names (0.23.1-11.6:glib2-tools-2.78.6-150600.4.16.1, 0.23.1-11.6:libgio-2_0-0-2.78.6-150600.4.16.1, …), 1965 product×package rows across 340 product lines (Container bci/kiwi, Container bci/spack, … (340 product lines)): Fixed 1744, Known Affected 221. https://www.suse.com/security/cve/CVE-2025-4373/
ubuntu medium CVE-2025-4373 medium priority: Ubuntu including 1 source packages (glib2.0), 10 status rows across 10 suites (bionic, focal, jammy, noble, oracular, plucky, questing, trusty, upstream, xenial): released 6, needs-triage 3, not-affected 1. https://ubuntu.com/security/CVE-2025-4373

Affected software / configurations for CVE-2025-4373

Vendor Product Version Raw CPE
No affected products in dataset.

References for CVE-2025-4373

URL Tags
https://access.redhat.com/errata/RHSA-2025:10855
https://access.redhat.com/errata/RHSA-2025:11140
https://access.redhat.com/errata/RHSA-2025:11327
https://access.redhat.com/errata/RHSA-2025:11373
https://access.redhat.com/errata/RHSA-2025:11374
https://access.redhat.com/errata/RHSA-2025:11662
https://access.redhat.com/errata/RHSA-2025:12275
https://access.redhat.com/errata/RHSA-2025:13335
https://access.redhat.com/errata/RHSA-2025:14988
https://access.redhat.com/errata/RHSA-2025:14989
https://access.redhat.com/errata/RHSA-2025:14990
https://access.redhat.com/errata/RHSA-2025:14991
https://access.redhat.com/security/cve/CVE-2025-4373
https://bugzilla.redhat.com/show_bug.cgi?id=2364265
https://gitlab.gnome.org/GNOME/glib/-/issues/3677
https://cert-portal.siemens.com/productcert/html/ssa-082556.html
https://cert-portal.siemens.com/productcert/html/ssa-089022.html
cvelogic Threat Intelligence