CVE-2026-20341: Deserialization of Untrusted Data
Source GCVE Database
Not known to be exploited · CVSS 9.1 Critical.
Data as of 31 Oct 2026, 20:20 UTC
- EPSS
- 0.6% chance of exploitation in 30 days – higher than 49% of CVEsExploit Prediction Scoring System: the likelihood attackers will use this flaw soon.
CVSS:3.1/AV:N/AC:L/PR:H/UI:N/S:C/C:H/I:H/A:HExploitation evidence
Disclosed: evidence found.
CVE published 16 Sep 2026
Detectable: no evidence on record.
No public nuclei template indexed
Weaponized: no evidence on record.
No public exploit code indexed in Metasploit or Exploit-DB
Exploited in the wildExploited: no evidence on record.
Not in CISA KEV and no source reports exploitation
Observed by OffSeq MirageSeen by Mirage: no evidence on record.
No attack traffic recorded by OffSeq Mirage sensors
A missing step is not evidence of safety. Sources: cve.org (opens in a new tab), the Metasploit, Exploit-DB and nuclei-templates index as of 31 Oct 2026.
What to do
Affected software
| Product | Affected | Fixed in |
|---|---|---|
| CiscoCisco Secure Firewall Management Center (FMC) | Affected
| Fixed in– |
AI-suggested
Since exploitation requires valid administrative credentials, limiting administrative access and monitoring for suspicious activity on managed Cisco FTD devices is advisable until an official fix is available.
Description
A critical vulnerability in the sftunnel inter-device communication protocol of Cisco Secure FMC Software allows an authenticated remote attacker with administrative credentials to gain root privileges. The flaw arises from unsecured deserialization of untrusted data over the sftunnel management connection. Exploitation requires sending crafted remote procedure calls (RPCs) via sftunnel. This vulnerability affects devices running Cisco Secure FMC Software and its high-availability peers.