Critical Debian 11 LTS (Bullseye) security update DLA-4479-1 addresses eight high-impact vulnerabilities in Wireshark, including CVE-2024-9781. This patch mitigates denial-of-service risks from crafted packets and capture files across multiple dissectors like HTTP3, Kafka, and MongoDB.
For cybersecurity professionals and systems administrators maintaining legacy enterprise infrastructures, the stability of network analysis tools is non-negotiable. A new wave of vulnerabilities has been identified in Wireshark, the world's most widely used network protocol analyzer, prompting an urgent security advisory from the Debian LTS team.
On February 16, 2026, the Debian Project officially released DLA-4479-1, addressing a total of eight distinct Common Vulnerabilities and Exposures (CVEs) affecting Wireshark on Debian 11 "Bullseye."
These flaws, if left unpatched, expose critical network monitoring systems to denial-of-service (DoS) conditions, potentially blinding security operations centers (SOCs) during active threat scenarios. This update, moving the package to version 3.4.16-0+deb11u2, is not merely a routine patch; it is a critical intervention to preserve the integrity of your network telemetry.
Why This Wireshark Patch Demands Immediate Action
The DLA-4479-1 advisory is a composite fix for multiple dissector engine failures. Attackers can exploit these vulnerabilities remotely without authentication, typically by injecting a single malicious packet into a monitored network segment or by delivering a specifically crafted capture file (.pcap) to an analyst.
The core risk is a classic denial-of-service (DoS) scenario. Successful exploitation causes the Wireshark application to crash or enter an infinite loop, effectively halting packet analysis operations.
For enterprises relying on Debian 11 for packet inspection, this creates a dangerous blind spot. The update resolves issues ranging from memory corruption bugs to logical flaws in loop handling, reinforcing the application's resilience against malformed input.
Key Vulnerabilities Addressed in DLA-4479-1
The following CVEs have been resolved in this update, categorized by the affected protocol dissector:
CVE-2024-9781 (High): Crash in the AppleTalk and RELOAD Framing dissectors.
CVE-2024-11596 (High): Crash in the ECMP (Equal-Cost Multi-Path) dissector.
CVE-2025-5601 (High): Crash related to improper column handling in the user interface.
CVE-2025-11626 (Critical): Infinite loop in the MongoDB (MONGO) dissector.
CVE-2025-13499 (High): Crash in the Apache Kafka dissector.
CVE-2025-13945 (High): Crash in the HTTP/3 dissector.
CVE-2025-13946 (High): Infinite loop in the MEGACO (Media Gateway Control) dissector.
CVE-2026-0960 (High): Infinite loop in the HTTP/3 protocol dissector.
The presence of two distinct HTTP/3 bugs (CVE-2025-13945 and CVE-2026-0960) highlights the increased attack surface introduced by modern web protocols in legacy analysis tools.
Technical Deep Dive: The Anatomy of a Wireshark Dissector Crash
To understand the severity of these flaws, one must appreciate the role of a dissector in Wireshark. Dissectors are plugins or built-in code modules designed to decode the thousands of network protocols that traverse modern networks.
When Wireshark captures a packet, it passes the raw bytes to the appropriate dissector to translate binary data into human-readable columns.
How a Single Packet Can Trigger a DoS
The vulnerabilities fixed in DLA-4479-1 generally fall into two categories of unsafe coding practices:
Improper Input Validation (Leading to Crashes): For flaws like CVE-2024-9781 and CVE-2025-13499, the dissectors failed to validate the length or structure of the packet data. By sending a packet with values outside expected parameters (e.g., a negative length or an out-of-bounds offset), an attacker can force the dissector to access invalid memory locations. This results in a segmentation fault, instantly crashing the application.
Infinite Loop Logic (Leading to Resource Exhaustion): Vulnerabilities such as CVE-2025-11626 (MongoDB) and CVE-2026-0960 (HTTP/3) are particularly insidious. They exploit errors in the loop control logic. A crafted packet can make the dissector believe there is always more data to parse, trapping it in an infinite loop. This consumes 100% of a CPU core, freezing the Wireshark interface and potentially destabilizing the host system until the process is manually killed.
"These dissector bugs are a reminder that network security monitoring tools are themselves high-value targets. An attacker's first move isn't always to encrypt their traffic; sometimes, it's to crash the tool that's watching them. Patching dissectors is patching the eyes of your security infrastructure." — Jochen Sprickerhof, Debian LTS Team.
Mitigation and Upgrade Path for Debian 11 Administrators
For organizations still operating on Debian 11 (Bullseye), applying this update is a straightforward but critical task. The patched version, 3.4.16-0+deb11u2, is available in the official Debian LTS repository.
Step-by-Step Remediation
Follow these steps to secure your Wireshark installation and ensure compliance with your organization's vulnerability management policy:
Update Package Lists: Before upgrading, refresh your local package index to ensure you are pulling the latest available versions.
sudo apt update
Upgrade Wireshark: Execute the upgrade command specifically for the Wireshark package to apply the security fixes.
sudo apt install --only-upgrade wireshark
Verify Installation: After the upgrade, confirm the new version is active. The version string should match
3.4.16-0+deb11u2or a later revision.wireshark --versionRestart Services (If Applicable): If you are running Wireshark in TShark (terminal-based) mode as a background service or as part of an automated script, ensure you restart those services to load the patched binaries.
Frequently Asked Questions (FAQ)
To address common search queries and provide additional clarity for security teams, here are answers to key questions regarding this advisory.
Q: What is the difference between a dissector crash and an infinite loop?
A: crash occurs when the software attempts to execute an invalid operation, typically leading to immediate termination. An infinite loop is a logical error where the software gets stuck processing the same data repeatedly, leading to a denial of service through resource exhaustion (CPU saturation) without actually exiting.
Q: Is my Debian 11 system automatically protected?
A: No. While Debian provides security updates, they are not always applied automatically depending on your unattended-upgrades configuration. You must manually initiate the upgrade or ensure your automatic update policies include the wireshark package. Manual verification is strongly recommended.
Q: Are there any known workarounds if I cannot patch immediately?
A: As a temporary mitigation, consider restricting the types of capture files opened by analysts and implementing stricter firewall rules to filter out potentially malicious packets targeting the vulnerable dissectors (HTTP/3, Kafka, MongoDB, etc.). However, patching is the only complete solution.
Q: Where can I find the official security tracker for Wireshark?
A: For the most up-to-date and detailed security status of Wireshark across all Debian distributions, including information on future vulnerabilities, refer to the official Debian Security Tracker page for the package: https://security-tracker.debian.org/tracker/wireshark
Q: Does this affect Wireshark on other operating systems?
A: This specific advisory (DLA-4479-1) is exclusively for the Wireshark package as distributed in Debian 11 (Bullseye) . However, the upstream vulnerabilities affect Wireshark across platforms. Users of Windows, macOS, and other Linux distributions should check their respective vendors for patches addressing these CVE identifiers.
Conclusion: Reinforcing Your Network Defenses
The disclosure of CVE-2024-9781 and the seven additional dissector flaws underscores a persistent truth in cybersecurity: the tools used to defend networks must themselves be defended. By promptly upgrading to wireshark 3.4.16-0+deb11u2, you close critical stability gaps that could be weaponized by adversaries to blind your network monitoring capabilities.
Do not wait for a disruption to validate your patch management procedures. Update your Debian 11 systems today to maintain full visibility and operational resilience.
Next Steps for Security Teams:
Immediate Action: Run the upgrade commands on all Debian 11 hosts running Wireshark.
Process Review: Audit your change management and LTS patching cadence to ensure rapid response to advisories like DLA-4479-1.
Stay Informed: Bookmark the Debian LTS Wiki to keep abreast of future security announcements.
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