Machine-written summary
Summary written by Claude Haiku from the source advisory. Not reviewed by a person.
Undertow (io.undertow:undertow-parent) versions up to and including 2.3.23.Final are vulnerable to HTTP request smuggling. A remote attacker can send a crafted header block terminator that some proxy servers interpret differently, which can lead to unauthorized access or manipulation of web requests. No fixed version is listed.
Not analysed yet
We haven’t published our analysis of this Advisory yet. Once a person has reviewed it, this page will say what’s vulnerable, what has to be true for your app to be affected, and how to check.
Severity and exploitation
| Score | Rating | CVSS | Vector | Source |
|---|---|---|---|---|
| 8.7 | High | 3.1 | CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:C/C:H/I:H/A:N | CNA (redhat) |
- CISA KEV Not listed.
- EPSS 0.0072, the 54th percentile, on 5 Nov 2026: FIRST’s estimate of the chance of exploitation in the next 30 days.
Timeline
- 27 Mar 2026, 16:13 UTC Confirmed by the CVE List
- 27 Mar 2026, 17:16 UTC Confirmed by NVD
- 27 Mar 2026, 18:31 UTC Confirmed by GitHub Advisory Database
- 31 Oct 2026, 14:17 UTC First seen by agentprime
- 31 Oct 2026, 14:17 UTC Confirmed by OSV
Sources
- GitHub Advisory Database: GHSA-3gv6-g396-9v4r
- OSV: GHSA-3gv6-g396-9v4r
- nvd.nist.gov/vuln/detail/CVE-2026-28367
- github.com/undertow-io/undertow/commit/3ece0bf2b2cf5e01db8ca25e41b831e66d3f5961
- github.com/undertow-io/undertow/commit/904e26f1be62fb00b440538608a9574839821878
- github.com/undertow-io/undertow/commit/c5dc41479e9c3576552d7e98e31bb1c237ae155e
- access.redhat.com/errata/RHSA-2026:25125
- access.redhat.com/errata/RHSA-2026:25126
- access.redhat.com/security/cve/CVE-2026-28367
- bugzilla.redhat.com/show_bug.cgi?id=2443260
- github.com/undertow-io/undertow