CVE-2026-20004
A vulnerability in the TLS library of Cisco IOS XE Software could allow an unauthenticated, adjacent attacker to exhaust the available…
- 7.4HighCVSS base score
- 0.19%Exploitation in 30 daysEPSS · top 92% of all CVEs
- NoKnown exploitednot in CISA's KEV catalog
- NonePublic exploitsnone known yet
Description
A vulnerability in the TLS library of Cisco IOS XE Software could allow an unauthenticated, adjacent attacker to exhaust the available memory of an affected device. This vulnerability is due to improper management of memory resources during TLS connection setup. An attacker could exploit this vulnerability by repeatedly triggering the conditions that cause the memory increase. This could be done in a variety of ways, such as by repeatedly attempting Extensible Authentication Protocol (EAP) authentication when local EAP is enabled on an affected device or by using a machine-in-the-middle attack and resetting TLS connections between the affected device and other devices. A successful exploit could allow the attacker to exhaust the available memory on an affected device, resulting in an unexpected reload and a denial of service (DoS) condition.
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 | High7.4 | CVSS:3.1/AV:A/AC:L/PR:N/UI:N/S:C/C:N/I:N/A:H |
| NVDNVD · Analyzed | 3.1 | High7.4 | CVSS:3.1/AV:A/AC:L/PR:N/UI:N/S:C/C:N/I:N/A:H |
- EPSS (exploitation in 30 days)
- 0.19% · top 92% of all CVEs (9 Nov 2026)
- CISA SSVC
- Exploitation: none · Automatable: no · Technical impact: partial
The list uses the assigner's score when there is one, then CISA's, then NVD's: High 7.4.
Affected products
- affected 16.9.1
- affected 16.9.2
- affected 16.9.1a
- affected 16.9.1b
- affected 16.9.1s
- affected 16.9.3
- affected 16.9.4
- affected 16.9.3a
- affected 16.9.5
- affected 16.9.5f
- affected 16.9.6
- affected 16.9.7
- affected 16.9.8
- affected 16.10.1
- affected 16.10.1a
- affected 16.10.1b
- affected 16.10.1s
- affected 16.10.1c
- affected 16.10.1e
- affected 16.10.1d
- affected 16.10.2
- affected 16.10.1f
- affected 16.10.1g
- affected 16.10.3
- affected 16.11.1
- affected 16.11.1a
- affected 16.11.1b
- affected 16.11.2
- affected 16.11.1s
- affected 16.12.1
- affected 16.12.1s
- affected 16.12.1a
- affected 16.12.1c
- affected 16.12.1w
- affected 16.12.2
- affected 16.12.1y
- affected 16.12.2a
- affected 16.12.3
- affected 16.12.8
- affected 16.12.2s
- and 140 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.
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-2026-15426 (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-2026-20004)Record last updated .