Swati KhandelwalJun 04, 2026Vulnerability / Network Security
Cisco has patched a bug in Unified Communications Manager that lets an unauthenticated attacker on the network write files to the box and, from there, climb to root.
It is tracked as CVE-2026-20230, and proof-of-concept exploit code is already public. Cisco's PSIRT says it has not seen the flaw used in attacks yet. The PoC shortens that runway.
The flaw is a server-side request forgery. Unified CM and its Session Management Edition fail to validate certain HTTP requests properly, so a crafted request can push the server into writing arbitrary files onto the underlying OS. Those files are the foothold. Cisco says they can be used later to escalate to root, the top privilege on the system.
That two-step is why the score and the rating disagree. The CVSS base is 8.6: it scores the file write (an integrity-only impact, no confidentiality or availability loss) but not the root escalation that follows. Cisco rated the advisory Critical anyway, since the end state is full root.
