# CVE-2026-76918: Wireshark SSH dissector heap buffer overflow in curve25519

Source: https://junglewise.ai/threats/cve-2026-76918-wireshark-ssh-dissector-heap-buffer-overflow-in-curve25519  
Publisher: Junglewise Threat Intelligence, https://junglewise.ai/threats  
Published: 2026-08-19. Updated: 2026-09-25  
License: CC BY 4.0 with a link back

CVE-2026-76918 · Severity: medium · CVSS 5.5 · Published 2026-08-19

Wireshark is a network protocol analyzer used to inspect and troubleshoot network traffic. The SSH protocol dissector contains a heap buffer overflow vulnerability when processing curve25519 key exchange, allowing an attacker to crash Wireshark by providing a malformed capture file or injecting a crafted network packet. This can disrupt incident response activities and network troubleshooting operations.

Technologies: [Wireshark](https://junglewise.ai/threats/technologies/wireshark). Vendors: [Wireshark](https://junglewise.ai/threats/vendors/wireshark).

## Quick answers

**Is CVE-2026-76918 exploited in the wild?** No. Junglewise Threat Intelligence has no report of CVE-2026-76918 being exploited in the wild.

**How severe is CVE-2026-76918?** Medium severity, with a CVSS score of 5.5, published 19 August 2026.

**Which products and versions are affected?** Wireshark 4.6.0 to 4.6.7, 4.4.0 to 4.4.17.

**Is there a fix for CVE-2026-76918?** A patch was published on 2026-08-12: Fixed in Wireshark 4.6.8 and 4.4.18 Junglewise finds every place you run it, drafts the upgrade and applies it once you approve.

**How is CVE-2026-76918 attacked?** It is attacked with local access, in a software library.

**Am I affected by CVE-2026-76918?** 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 heap buffer overflow in the SSH dissector's curve25519 key exchange handling. The root cause is in `ssh_kex_shared_secret()` which allocates a buffer sized from an attacker-controlled length value read from the wire (1–31 bytes), then passes it to `crypto_scalarmult_curve25519()` which unconditionally writes and reads exactly 32 bytes. This causes out-of-bounds heap read and write of up to 31 bytes. The vulnerability can be triggered by opening a capture file or processing a network packet with malformed curve25519 key material; no authentication or user interaction is required beyond opening the file. An attacker can crash Wireshark, causing denial of service. Patches are available in Wireshark 4.6.8 and 4.4.18.

## Affected products

- Wireshark Wireshark 4.6.0 to 4.6.7, 4.4.0 to 4.4.17

## Timeline

- 2026-08-12: disclosed
- 2026-08-12: patched: Fixed in Wireshark 4.6.8 and 4.4.18

## References

- [https://gitlab.com/wireshark/wireshark/-/work_items/21465](https://gitlab.com/wireshark/wireshark/-/work_items/21465)
- [https://www.wireshark.org/security/wnpa-sec-2026-85.html](https://www.wireshark.org/security/wnpa-sec-2026-85.html)

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