CVE-2026-24881 – This vulnerability in GnuPG allows attackers to... (How to Fix)

Q: What is the severity of CVE-2026-24881?

CVE-2026-24881 has a CVSS score of 8.1 (HIGH). This vulnerability in GnuPG allows attackers to trigger a stack-based buffer overflow by sending specially crafted CMS/S-MIME messages with oversized wrapped session keys. This can lead to denial of service or potentially remote code execution. Systems running vulnerable versions of GnuPG that process CMS/S-MIME messages are affected.

📋 TL;DR

This vulnerability in GnuPG allows attackers to trigger a stack-based buffer overflow by sending specially crafted CMS/S-MIME messages with oversized wrapped session keys. This can lead to denial of service or potentially remote code execution. Systems running vulnerable versions of GnuPG that process CMS/S-MIME messages are affected.

💻 Affected Systems

Products:

GnuPG (gpg-agent)

Versions: All versions before 2.5.17

Operating Systems: Linux, Unix-like systems, Windows, macOS

Default Config Vulnerable: ⚠️ Yes

Notes: Only affects systems using CMS/S-MIME message processing via gpg-agent's PKDECRYPT--kem=CMS functionality.

📦 What is this software?

Gnupg by Gnupg

View all CVEs affecting Gnupg →

Gpg4win by Gpg4win

View all CVEs affecting Gpg4win →

⚠️ Risk & Real-World Impact

🔴

Worst Case

Remote code execution with the privileges of the gpg-agent process, potentially leading to full system compromise.

🟠

Likely Case

Denial of service through gpg-agent crashes, disrupting encryption/decryption operations.

🟢

If Mitigated

Limited impact if systems don't process untrusted CMS/S-MIME messages or have network filtering in place.

🌐 Internet-Facing: MEDIUM - Requires processing of crafted CMS messages, which typically come from email or network services.

🏢 Internal Only: LOW - Internal systems are less likely to receive malicious CMS messages unless targeted.

🎯 Exploit Status

Public PoC: ✅ No

Weaponized: UNKNOWN

Unauthenticated Exploit: ⚠️ Yes

Complexity: MEDIUM

Exploitation requires sending crafted CMS messages to trigger the buffer overflow. No public exploit code is currently available.

🛠️ Fix & Mitigation

✅ Official Fix

Patch Version: 2.5.17

Vendor Advisory: https://dev.gnupg.org/T8044

Restart Required: Yes

Instructions:

1. Download GnuPG 2.5.17 or later from https://gnupg.org/download. 2. Stop gpg-agent processes. 3. Install the updated version. 4. Restart gpg-agent and related services.

🔧 Temporary Workarounds

Disable CMS/S-MIME processing

all

Configure gpg-agent to reject CMS/S-MIME messages if not required

gpgconf --kill gpg-agent
Add 'disable-cms' to gpg-agent.conf

Network filtering

all

Block or filter incoming CMS/S-MIME messages at network boundaries

🧯 If You Can't Patch

Implement strict input validation for CMS/S-MIME messages
Monitor gpg-agent processes for crashes and restart automatically

🔍 How to Verify

Check if Vulnerable:

Check GnuPG version with 'gpg --version' and verify it's below 2.5.17

Check Version:

gpg --version | head -1

Verify Fix Applied:

Confirm version is 2.5.17 or higher with 'gpg --version'

📡 Detection & Monitoring

Log Indicators:

gpg-agent crash logs
segmentation fault errors in system logs
unexpected gpg-agent restarts

Network Indicators:

Unusually large CMS/S-MIME messages
Multiple failed decryption attempts

SIEM Query:

process:gpg-agent AND (event_id:1000 OR signal:SIGSEGV)

📊 Metadata

CVE ID: CVE-2026-24881

CVSS v3 Score: 8.1 (HIGH)

CVSS Vector: CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:H

CWE: CWE-121

EPSS Score: 0.13% exploit probability (33th percentile)

Published: January 27, 2026

Last Updated: February 12, 2026

🔗 References

https://dev.gnupg.org/T8044 Exploit,Product
https://www.openwall.com/lists/oss-security/2026/01/27/8 Mailing List,Third Party Advisory

📤 Share & Export

📄 Export Markdown 📋 Export JSON

🔗 Related Vulnerabilities

If you're affected by CVE-2026-24881, you might also want to check these: