CVE-2025-11021: libsoup Information Disclosure Vulnerability

CVE-2025-11021 Overview

A flaw was found in the cookie date handling logic of the libsoup HTTP library, widely used by GNOME and other applications for web communication. When processing cookies with specially crafted expiration dates, the library may perform an out-of-bounds memory read. This flaw could result in unintended disclosure of memory contents, potentially exposing sensitive information from the process using libsoup.

Critical Impact

An attacker can exploit this out-of-bounds read vulnerability remotely over the network without authentication to potentially leak sensitive process memory, including credentials, session tokens, or other confidential data from applications using the libsoup library.

Affected Products

• libsoup HTTP library
• GNOME applications using libsoup
• Red Hat Enterprise Linux distributions (multiple versions addressed in security advisories)

Discovery Timeline

• 2025-09-26 - CVE-2025-11021 published to NVD
• 2026-03-19 - Last updated in NVD database

Technical Details for CVE-2025-11021

Vulnerability Analysis

This vulnerability is classified as CWE-125 (Out-of-Bounds Read), which occurs when the software reads data past the end or before the beginning of an intended buffer. In the context of libsoup, the flaw resides in the cookie date parsing functionality that handles HTTP cookie expiration timestamps.

When a malicious server sends an HTTP response containing a Set-Cookie header with a specially crafted expiration date value, the libsoup library's date parsing routine fails to properly validate the input boundaries before reading memory. This allows an attacker to trigger reads beyond the allocated buffer, potentially exposing adjacent memory contents.

The vulnerability can be exploited remotely over the network without requiring any user interaction or authentication. Since libsoup is a foundational library used by many GNOME desktop applications and other software for HTTP communication, the attack surface is considerable. Any application that connects to attacker-controlled servers and processes cookies could be affected.

Root Cause

The root cause of this vulnerability lies in insufficient boundary checking within libsoup's cookie date parsing logic. The parsing routine handles various date format components (day, month, year, time) but fails to properly validate string lengths and offsets before accessing memory. When processing malformed date strings with unexpected or truncated format specifiers, the parser continues reading beyond the intended buffer boundaries.

Attack Vector

An attacker can exploit this vulnerability by setting up a malicious web server that responds with HTTP cookies containing specially crafted expiration date values. When a victim application using libsoup connects to this server and processes the response, the vulnerable date parsing code is triggered.

The attack can be conducted in several scenarios:

• A user browsing to a malicious website using a libsoup-based browser or application
• An application making automated HTTP requests to attacker-controlled endpoints
• Man-in-the-middle scenarios where an attacker injects malicious cookie headers

The out-of-bounds read could expose sensitive data residing in adjacent memory regions, such as authentication tokens, session data, encryption keys, or other application secrets. The attacker receives this information through the resulting application behavior or through timing/side-channel analysis depending on how the leaked memory is subsequently used.

Detection Methods for CVE-2025-11021

Indicators of Compromise

• Unusual HTTP responses containing Set-Cookie headers with malformed or abnormally long date values
• Application crashes or unexpected behavior following HTTP communications
• Memory access violations logged in system journals from libsoup-dependent applications
• Network traffic to suspicious endpoints containing unusual cookie header patterns

Detection Strategies

• Monitor application logs for segmentation faults or memory access errors in processes using libsoup
• Deploy web application firewalls (WAF) to inspect and filter HTTP responses with malformed cookie headers
• Utilize endpoint detection and response (EDR) solutions to detect abnormal memory access patterns
• Implement network intrusion detection systems (NIDS) rules to flag suspicious Set-Cookie header formats

Monitoring Recommendations

• Enable verbose logging for applications using libsoup to capture HTTP header details
• Configure system auditing to alert on memory violations from GNOME and related applications
• Monitor package management logs for libsoup version changes to ensure patches are applied
• Use SentinelOne's behavioral AI to detect anomalous process memory access patterns indicative of exploitation

How to Mitigate CVE-2025-11021

Immediate Actions Required

• Update libsoup to the latest patched version provided by your distribution
• Apply Red Hat security advisories if running RHEL or compatible distributions
• Restrict network access for applications using libsoup until patches can be applied
• Consider using application sandboxing to limit potential information disclosure impact

Patch Information

Red Hat has released multiple security advisories addressing this vulnerability. Organizations running Red Hat Enterprise Linux or compatible distributions should apply the relevant updates:

• Red Hat Security Advisory RHSA-2025:18183
• Red Hat Security Advisory RHSA-2025:19713
• Red Hat Security Advisory RHSA-2025:19714
• Red Hat Security Advisory RHSA-2025:20959
• Red Hat Security Advisory RHSA-2025:21032

Additional details are available at the Red Hat CVE Description for CVE-2025-11021 and the upstream GNOME Issue #459.

Workarounds

• Implement network-level filtering to block or sanitize HTTP responses with malformed Set-Cookie headers
• Disable cookie processing in libsoup-based applications where cookies are not required for functionality
• Use a proxy or content inspection solution to validate HTTP responses before they reach vulnerable applications
• Deploy application-level sandboxing using technologies like Flatpak or containers to limit memory exposure

# Example: Update libsoup on Red Hat-based systems
sudo dnf update libsoup --refresh

# Verify the installed version includes the security fix
rpm -q libsoup

# Check system logs for any prior exploitation attempts
journalctl -u gdm --since "1 week ago" | grep -i "memory\|segfault\|libsoup"