CVE-2026-20104
A vulnerability in the bootloader of Cisco IOS XE Software for Cisco Catalyst 9200 Series Switches, Cisco Catalyst ESS9300 Embedded Series…
- 6.1MediumCVSS base score
- 0.16%Exploitation in 30 daysEPSS · top 94% of all CVEs
- NoKnown exploitednot in CISA's KEV catalog
- NonePublic exploitsnone known yet
Description
A vulnerability in the bootloader of Cisco IOS XE Software for Cisco Catalyst 9200 Series Switches, Cisco Catalyst ESS9300 Embedded Series Switches, Cisco Catalyst IE9310 and IE9320 Rugged Series Switches, and Cisco IE3500 and IE3505 Rugged Series Switches could allow an authenticated, local attacker with level-15 privileges or an unauthenticated attacker with physical access to an affected device to execute arbitrary code at boot time and break the chain of trust. This vulnerability is due to insufficient validation of software at boot time. An attacker could exploit this vulnerability by manipulating the loaded binaries on an affected device to bypass some of the integrity checks that are performed during the boot process. A successful exploit could allow the attacker to execute code that bypasses the requirement to run Cisco-signed images. Cisco has assigned this security advisory a Security Impact Rating (SIR) of High rather than Medium as the score indicates because this vulnerability allows an attacker to bypass a major security feature of a device.
Timeline
ID reserved
By cisco
- 6 months later
· 6 months later
Published
- 1 day later
· 1 day later
Record updated
Changes after publication (a new score, a public exploit, EPSS crossing 1, 10 or 50 %, leaving KEV) are kept since November 2026; earlier ones are not known.
Scores
| Scored by | CVSS | Score | Vector |
|---|---|---|---|
| ciscoCNA (assigner) | 3.1 | Medium6.1 | CVSS:3.1/AV:P/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N |
| NVDNVD · Analyzed | 3.1 | Medium6.1 | CVSS:3.1/AV:P/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N |
- EPSS (exploitation in 30 days)
- 0.16% · top 94% of all CVEs (12 Nov 2026)
- CISA SSVC
- Exploitation: none · Automatable: no · Technical impact: total
The list uses the assigner's score when there is one, then CISA's, then NVD's: Medium 6.1.
Affected products
- affected 16.12.8
- affected 16.12.6
- affected 16.12.6a
- affected 16.12.7
- affected 17.3.3
- affected 17.3.4
- affected 17.3.5
- affected 17.3.6
- affected 17.3.4b
- affected 17.3.7
- affected 17.3.8
- affected 17.3.8a
- affected 17.4.1
- affected 17.5.1
- affected 17.6.1
- affected 17.6.2
- affected 17.6.3
- affected 17.6.1y
- affected 17.6.4
- affected 17.6.5
- affected 17.6.6
- affected 17.6.6a
- affected 17.6.5a
- affected 17.6.7
- affected 17.6.8
- affected 17.7.1
- affected 17.7.1a
- affected 17.10.1
- affected 17.8.1
- affected 17.8.1a
- affected 17.9.1
- affected 17.9.2
- affected 17.9.1a
- affected 17.9.3
- affected 17.9.4
- affected 17.9.5
- affected 17.9.4a
- affected 17.9.5b
- affected 17.9.6
- affected 17.9.6a
- and 19 more
What to do
Exploitation: The Cisco Product Security Incident Response Team (PSIRT) is not aware of any public announcements or malicious use of the vulnerability that is described in this advisory.
References
Sources
The same CVE in the primary databases and aggregators, to check against.
- CVE.org record (opens in a new tab)
- CVE List JSON (GitHub) (opens in a new tab)
- NVD (opens in a new tab)
- FIRST EPSS (opens in a new tab)
- EUVD EUVD-2026-15435 (opens in a new tab)
- OSV.dev (opens in a new tab)
- GitHub Advisories (opens in a new tab)
- CIRCL Vulnerability-Lookup (opens in a new tab)
Badge for a README or a ticket
[](https://cveledger.app/cve/CVE-2026-20104)Record last updated .