CVE-2025-9784
Medium
Elevated severity or exploit probability.
CVSS base
7.5
HIGH
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
EPSS — probability of exploitation (30 days)
2.3%
82.7th percentile
CISA KEV
Not listed
Weakness / dates
CWE-404
Published 2025-09-02 · modified 2026-09-04
CVSS breakdown
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
| Attack Vector | N | Network |
| Attack Complexity | L | Low |
| Privileges Required | N | None |
| User Interaction | N | None |
| Scope | U | Unchanged |
| Confidentiality | N | None |
| Integrity | N | None |
| Availability | H | High |
Timeline
- 2025-09-02 — Published (NVD)
- 2026-09-04 — Last modified (NVD)
Description
A flaw was found in Undertow where malformed client requests can trigger server-side stream resets without triggering abuse counters. This issue, referred to as the "MadeYouReset" attack, allows malicious clients to induce excessive server workload by repeatedly causing server-side stream aborts. While not a protocol bug, this highlights a common implementation weakness that can be exploited to cause a denial of service (DoS).
Affected
References
- https://access.redhat.com/errata/RHSA-2025:23143
- https://access.redhat.com/errata/RHSA-2026:0383
- https://access.redhat.com/errata/RHSA-2026:0384
- https://access.redhat.com/errata/RHSA-2026:0386
- https://access.redhat.com/errata/RHSA-2026:33371
- https://access.redhat.com/errata/RHSA-2026:33372
- https://access.redhat.com/errata/RHSA-2026:3889
- https://access.redhat.com/errata/RHSA-2026:3891
- https://access.redhat.com/errata/RHSA-2026:3892
- https://access.redhat.com/errata/RHSA-2026:4915
- https://access.redhat.com/errata/RHSA-2026:4916
- https://access.redhat.com/errata/RHSA-2026:4917
- https://access.redhat.com/errata/RHSA-2026:4924
- https://access.redhat.com/security/cve/CVE-2025-9784
- https://bugzilla.redhat.com/show_bug.cgi?id=2392306
- https://github.com/undertow-io/undertow/pull/1778
- https://github.com/undertow-io/undertow/releases/tag/2.2.38.Final
- https://issues.redhat.com/browse/UNDERTOW-2598
- https://kb.cert.org/vuls/id/767506
- https://www.kb.cert.org/vuls/id/767506