CVE-2026-76756: Gammu SMS Daemon Buffer Overflow Flaw

CVE-2026-76756 Overview

CVE-2026-76756 is a memory corruption vulnerability [CWE-119] affecting the Drupal Gammu SMS Daemon contributed module. The flaw involves improper restriction of operations within the bounds of a memory buffer. Exploitation requires network access and high privileges, and successful attacks compromise both confidentiality and integrity of the affected system.

The vulnerability affects Gammu SMS Daemon versions distributed through the Drupal contributed module ecosystem. Attack complexity is high, which reduces the likelihood of opportunistic exploitation but does not eliminate targeted risk.

Critical Impact
Authenticated attackers with elevated privileges can trigger memory corruption over the network, resulting in disclosure and modification of sensitive data handled by the Gammu SMS Daemon module.

Affected Products

Drupal Gammu SMS Daemon module
Drupal sites using the Gammu SMS Daemon contributed module
Refer to the Drupal Security Advisory for exact version ranges

Discovery Timeline

2026-09-02 - CVE CVE-2026-76756 published to NVD
2026-09-02 - Last updated in NVD database

Technical Details for CVE-2026-76756

Vulnerability Analysis

The vulnerability is classified under [CWE-119], Improper Restriction of Operations within the Bounds of a Memory Buffer. This category covers buffer overflows and related conditions where code reads or writes outside the intended memory region. In the Gammu SMS Daemon module, memory boundary handling fails under specific conditions that an authenticated attacker can reach over the network.

Successful exploitation can corrupt adjacent memory structures. This corruption can expose sensitive data processed by the daemon, including SMS content, credentials, or session data. Attackers can also modify data in transit or in memory, breaking the integrity of message handling.

The attack requires high privileges on the target Drupal site, which limits exposure to accounts already trusted with administrative or module-level access. Availability is not affected according to the published metrics.

Root Cause

The root cause lies in memory buffer handling within the Gammu SMS Daemon module code paths. Input processed by the module is not properly bounded against the destination buffer size. Detailed technical analysis is provided in the vendor advisory rather than in this article, since no verified proof-of-concept code is available.

Attack Vector

Exploitation occurs over the network against a Drupal site running the vulnerable module. The attacker must already hold high-privilege credentials on the target application. No user interaction is required. Because attack complexity is high, exploitation depends on specific conditions in the target environment such as module configuration, message queue state, or input format.

No public proof-of-concept, exploit code, or CISA KEV listing exists for this issue at the time of publication. See the Drupal Security Advisory for authoritative technical details.

Detection Methods for CVE-2026-76756

Indicators of Compromise

Unexpected crashes, restarts, or abnormal termination of the Gammu SMS Daemon process
Anomalous SMS queue entries or message content inconsistent with normal application behavior
Administrative or module-management actions from accounts that do not typically perform them

Detection Strategies

Monitor Drupal audit logs for high-privilege account activity interacting with the Gammu SMS Daemon module endpoints
Inspect web server access logs for repeated or malformed requests targeting SMS daemon module routes
Correlate process crash telemetry on the Drupal host with authenticated administrative sessions

Monitoring Recommendations

Enable verbose logging for the Gammu SMS Daemon module and forward logs to a centralized SIEM
Alert on segmentation faults or abnormal exits of the gammu-smsd process
Track privilege changes and role assignments in Drupal to detect misuse of high-privilege accounts

How to Mitigate CVE-2026-76756

Immediate Actions Required

Apply the fixed version of the Gammu SMS Daemon module as published in the Drupal Security Advisory
Audit accounts with high privileges on affected Drupal sites and revoke access that is not required
Rotate credentials for administrative accounts on hosts running the vulnerable module

Patch Information

Drupal has published a security advisory for this issue. Site administrators should update the Gammu SMS Daemon contributed module to the version identified in the Drupal Security Advisory. Verify module version alignment across all Drupal environments including staging and disaster-recovery instances.

Workarounds

Temporarily disable the Gammu SMS Daemon module on Drupal sites where patching cannot be applied immediately
Restrict network access to Drupal administrative endpoints using firewall rules or a web application firewall
Enforce multi-factor authentication for all high-privilege Drupal accounts to reduce the risk of credential-based exploitation

bash

# Configuration example
# Disable the Gammu SMS Daemon module via Drush until the patched version is deployed
drush pm:uninstall gammu_smsd
drush cache:rebuild