CVE-2026-15565: undertow Classic Buffer Overflow
CVSS: 7.5v3.1HighAwaiting analysis
AliasesUBUNTU-CVE-2026-15565DEBIAN-CVE-2026-15565
Published 11-08-2026Last modified 15-10-2026
Vulnerability summary
CVE-2026-15565 is a high (CVSS 7.5) Classic Buffer Overflow vulnerability in undertow. EPSS estimates a 0.61% chance of exploitation in the next 30 days, higher than 48% of scored vulnerabilities.
CVSS score
7.5/10
010
High · v3.1 (CVE.org)EPSS score
0.61%
0%100%
Low · +0.10 pp in 30 daysKEVNot listedIn no KEV catalog
RansomwareNone recordedNo known use recorded
Public exploits0No public exploits recorded
Advisory lineage
Upstream 0 · Downstream 6Timeline
- 11-08-2026PublishedVulnerability first disclosed.
- 15-10-2026Last modifiedVulnerability information updated.
Description
A flaw was found in Undertow. A remote attacker can cause Out of Memory on websockets endpoint without authentication on any @ServerEndpoint class that has any @OnMessage method. This allows an attacker to cause Denial of Service attack without authentication and using only a standard WebSocket handshake.
CVSS metrics
4 scores · 4 sources · 1 versionHigh 7.5Preferred score · CVE.org (CNA)
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:HSourcesAll 4 agree
- OSV · UbuntuEcosystem advisory · calculated7.5HighCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
- OSV · DebianEcosystem advisory · calculated7.5HighCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
- NVDNIST7.5HighCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
EPSS trend
Probability
0.61%
Chance of exploitation in the next 30 days
Percentile
48%
Versus all other CVEs
30-day change
+0.10 pp
From 0.51% on 18-09-2026
18-09-202618-10-2026
EPSS score0.61%
Known exploited
Compare KEV catalogsNot in any of the 3 tracked catalogs.
Public exploits
0 foundNo public exploits indexed.
Weaknesses
CWE · root causeAffected systems
Debian1 product
- undertowAll versions (No fix recorded)
Ubuntu1 product
- undertowAll versions (No fix recorded)
2 vendors · 2 products
