Is CVE-2026-76921 exploited in the wild?

No. Junglewise Threat Intelligence has no report of CVE-2026-76921 being exploited in the wild.

How severe is CVE-2026-76921?

Medium severity, with a CVSS score of 5.5, published 19 August 2026.

Which products and versions are affected?

Wireshark 4.4.0 to 4.4.18, 4.6.0 to 4.6.7.

Is there a fix for CVE-2026-76921?

No fixed version is recorded yet. Check the vendor's advisory in the references below. If you run it, Junglewise drafts a mitigation that fits your setup and applies it once you approve, with senior security engineers behind it.

How is CVE-2026-76921 attacked?

It is attacked over the network or from the adjacent network, in a software library.

Am I affected by CVE-2026-76921?

Check whether you run Wireshark at an affected version. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.

CVE-2026-76921: Wireshark CMS protocol dissector heap-use-after-free

CVE-2026-76921 · Severity: medium · CVSS 5.5 · Published 2026-08-19

Wireshark is a network protocol analyzer widely used to capture and examine network traffic. The CMS (Cryptographic Message Syntax) dissector contains a use-after-free flaw that allows an attacker to crash Wireshark by sending specially crafted network packets. An attacker can exploit this vulnerability by opening a malicious packet capture file or by sending crafted LDAP packets over a network, causing the application to crash and denying service to legitimate users.

Technologies: Wireshark. Vendors: Wireshark.

Quick answers

Is CVE-2026-76921 exploited in the wild?: No. Junglewise Threat Intelligence has no report of CVE-2026-76921 being exploited in the wild.
How severe is CVE-2026-76921?: Medium severity, with a CVSS score of 5.5, published 19 August 2026.
Which products and versions are affected?: Wireshark 4.4.0 to 4.4.18, 4.6.0 to 4.6.7.
Is there a fix for CVE-2026-76921?: No fixed version is recorded yet. Check the vendor's advisory in the references below. If you run it, Junglewise drafts a mitigation that fits your setup and applies it once you approve, with senior security engineers behind it.
How is CVE-2026-76921 attacked?: It is attacked over the network or from the adjacent network, in a software library.
Am I affected by CVE-2026-76921?: Check whether you run Wireshark at an affected version. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.

Technical details

The vulnerability is a use-after-free bug (CWE-416) in Wireshark's CMS protocol dissector that stores packet-scoped tree pointers in file-static variables (cap_tree and top_tree). After a packet's memory pool is reset, these non-NULL pointers remain and are reused by subsequent packets, causing heap-use-after-free conditions when RC2 parameter decoding or eContent callbacks attempt to append text to or dispatch through freed proto_item structures. The flaw affects versions 4.6.0–4.6.7 and 4.4.0–4.4.18. Attack vectors include opening a crafted PCAP file (requires user interaction) or live packet dissection over LDAP/UDP (no interaction needed). The crash is deterministic and confirmed via ASan heap-use-after-free reports in proto_item_append_text() and call_dissector_work(). Patches moving these pointers into packet-scoped cms_private_data structures are available.

Affected products

Wireshark Wireshark 4.4.0 to 4.4.18, 4.6.0 to 4.6.7

Timeline

2026-08-19: disclosed

References

This page as Markdown. Free to reuse under CC BY 4.0 with a link back.