CVE-2025-60018: glib-networking Buffer Overflow Flaw

CVE-2025-60018 Overview

CVE-2025-60018 affects the glib-networking library, specifically its OpenSSL backend. The flaw stems from the backend failing to properly check the return value of a call to BIO_write(). This missing validation leads to an out-of-bounds read [CWE-125] during TLS data handling. The issue is tracked under Red Hat Bugzilla #2398135 and GNOME issue #226. Applications that rely on glib-networking compiled against OpenSSL — rather than the default GnuTLS backend — inherit the exposure when they process attacker-influenced TLS traffic.

Critical Impact
A remote attacker can trigger an out-of-bounds read in the OpenSSL backend of glib-networking, leading to limited information disclosure and potential process disruption during TLS operations.

Affected Products

glib-networking when built with the OpenSSL backend
Red Hat Enterprise Linux distributions shipping affected glib-networking packages
GNOME platform components relying on glib-networking for TLS transport

Discovery Timeline

2025-09-25 - CVE CVE-2025-60018 published to NVD
2026-06-30 - Last updated in NVD database

Technical Details for CVE-2025-60018

Vulnerability Analysis

The defect lives in the OpenSSL TLS backend of glib-networking, the library that provides TLS and DNS support to GLib-based applications. The backend calls BIO_write() to feed data into an OpenSSL memory BIO but does not verify the return value. BIO_write() can return values less than the requested length, zero, or a negative value on error. Downstream code treats the write as if the full buffer had been consumed. Subsequent processing then reads past the end of the tracked buffer, producing an out-of-bounds read classified as [CWE-125].

The read can leak adjacent process memory contents into TLS state or trigger abnormal termination of the consuming application. Exploitation requires network-adjacent conditions where the attacker can influence TLS frame sizing or timing. Attack complexity is high, and no user interaction is required.

Root Cause

The root cause is missing return-value validation on BIO_write(). OpenSSL API contracts require callers to inspect the return code before advancing internal offsets. The affected code path assumes success and continues to reference bytes beyond the write boundary.

Attack Vector

An attacker delivers crafted TLS records to an application using the OpenSSL-backed glib-networking. The malformed record shape causes BIO_write() to short-write or fail. The unchecked path then reads out of bounds. Impacts are limited to confidentiality of small memory regions and availability of the affected process.

No verified proof-of-concept code is publicly available. See the Red Hat CVE-2025-60018 Advisory and the GNOME Issue #226 Discussion for technical details.

Detection Methods for CVE-2025-60018

Indicators of Compromise

Unexpected crashes or SIGSEGV signals in processes linked against glib-networking with OpenSSL support
Repeated TLS handshake failures originating from a narrow set of remote endpoints
AddressSanitizer or Valgrind reports flagging out-of-bounds reads inside gtlsconnection-openssl code paths

Detection Strategies

Inventory installed glib-networking packages and identify builds compiled with the OpenSSL backend rather than GnuTLS
Enable core dump collection on applications using GLib TLS to capture faults referencing BIO_write call sites
Correlate TLS error logs with process termination events to identify repeatable triggers

Monitoring Recommendations

Track distribution security feeds from Red Hat and GNOME for patched glib-networking versions
Alert on abnormal exit codes for long-running services that depend on GLib TLS, such as GNOME Online Accounts or libsoup consumers
Monitor for anomalous inbound TLS traffic patterns targeting services known to use the OpenSSL backend

How to Mitigate CVE-2025-60018

Immediate Actions Required

Apply updated glib-networking packages from your Linux distribution once available
Identify applications built against the OpenSSL backend and prioritize their remediation
Restrict exposure of affected services to untrusted networks until patches are deployed

Patch Information

Refer to the Red Hat CVE-2025-60018 Advisory and the Red Hat Bug Report #2398135 for package fix status. Upstream progress is tracked in the GNOME Issue #226 Discussion. The fix adds proper return-value handling for BIO_write() in the OpenSSL backend.

Workarounds

Where feasible, switch to the GnuTLS backend of glib-networking, which is the upstream default and is not affected by this specific defect
Place vulnerable services behind a reverse proxy that terminates TLS using an unaffected stack
Apply network segmentation to limit which peers can initiate TLS sessions to affected processes

bash

# Example: verify installed glib-networking version and TLS backend on Red Hat systems
rpm -q glib-networking
GIO_MODULE_DIR=$(pkg-config --variable=giomoduledir gio-2.0)
ls "$GIO_MODULE_DIR" | grep -i tls