Cisco Catalyst SD-WAN Manager: security flaw used in attacks
OFFICIAL NAME: Cisco Catalyst SD-WAN Manager Hex Encoding Vulnerability
WHAT IT IS · VPN, FIREWALL OR GATEWAYIt sits at the edge of your network and faces the internet, so attackers can reach it directly.
DO THIS FIRSTIf you have it, patch it today. If you cannot, block access to it from the internet until you can. Not sure if you use it? Send this page to your IT provider or security lead and ask.
TECHNICAL SUMMARY Cisco Catalyst SD-WAN Manager contains a hex encoding vulnerability that could allow an unauthenticated, remote attacker to access an affected system with privileges of the admin user due to improper handling of URI encoding in an HTTP request.
WHY THIS VERDICT Attacks are confirmed. The vulnerability is 41 days old, so many systems are likely still unpatched. It affects a product that faces the internet or gives remote access. The severity score is critical (9.8).
WHY IT RANKS HERE Exploitation is confirmed by an authoritative source. The product faces the internet or gives remote access.
- HIGHEST CONFIRMED RUNG
- EXPLOITED
- CISA KEV
- LISTED
- EXPLOIT CODE
- PROOF OF CONCEPT
How far has it climbed?
01 TALK
▨ REPORTED, NOT CONFIRMEDNEWEST EVIDENCE · 1 SOURCECVE-2026-76504 discussed publicly (CIRCL sighting). CVE-2026-76504 discussed publicly (CIRCL sighting).
02 EXPOSED
□ NOT TRACKED YETNO SOURCE FOR THIS STEP YETWe have no source that counts exposed systems yet. Internet scan data needs a partnership we do not have. No evidence here does not mean nothing is exposed.
03 TRIED
■ CONFIRMEDNEWEST EVIDENCE · 2 INDEPENDENT SOURCESAttacks that worked are confirmed (step 4), so attempts count as confirmed too.
04 EXPLOITED
■ CONFIRMEDNEWEST EVIDENCE · 2 INDEPENDENT SOURCESCISA Vulnrichment marks CVE-2026-76504 as actively exploited. Cisco Catalyst SD-WAN Manager contains a hex encoding vulnerability that could allow an unauthenticated, remote attacker to access an affected system with privileges of the admin user due to improper handling of URI encoding in an HTTP request.
05 DAMAGE
□ NOT TRACKED YETNO SOURCE FOR THIS STEP YETBreach notices and filings rarely name the flaw that was used, so we cannot link them to this event yet. No evidence here does not mean no harm.
When each thing happened
- DISCLOSED
- EXPLOIT CODE PUBLIC
- FIRST ATTACK REPORT
- CISA KEV LISTING
- US FEDERAL DEADLINE
THE FIX
CISA's instruction: apply the vendor's fix, or stop using the product if no fix exists. The deadline CISA set for US federal agencies, Oct 3, 2026, has passed. It is a US government deadline; use it as a guide.
Questions to ask this week
- Do we run Cisco Catalyst SD-WAN Manager? If yes, is it patched or cut off from the internet?
- Who owns fixing it, and by what date?
- Have we checked for signs of attack since the first report, not just since the patch?
How it unfolded
- Attack activity. SEP 29, 2026Cisco Catalyst SD-WAN Manager Hex Encoding Vulnerability
- Attack activity. SEP 30, 2026CISA Vulnrichment marks CVE-2026-76504 as actively exploited
- SEP 30, 20263 public GitHub repositories claim a proof of concept for CVE-2026-76504
- OCT 22, 2026Public proof of concept for CVE-2026-76504 (CIRCL sighting) (2 reports, latest NOV 4)
- OCT 28, 2026CVE-2026-76504 discussed publicly (CIRCL sighting) (9 reports, latest NOV 8)
SOURCES
- [1] CIRCL Vulnerability-Lookup sightings: CVE-2026-76504 discussed publicly (CIRCL sighting), NOV 8
- [2] CIRCL Vulnerability-Lookup sightings: Public proof of concept for CVE-2026-76504 (CIRCL sighting), NOV 4
- [3] PoC-in-GitHub: 3 public GitHub repositories claim a proof of concept for CVE-2026-76504, SEP 30
- [4] CVE List V5 and CISA Vulnrichment: CISA Vulnrichment marks CVE-2026-76504 as actively exploited, SEP 30
- [5] CISA Known Exploited Vulnerabilities: Cisco Catalyst SD-WAN Manager Hex Encoding Vulnerability, SEP 29
- [6] CIRCL Vulnerability-Lookup sightings: 9 more reports