Critical
undertow — security advisory
A flaw was found in Undertow. A remote attacker can exploit this vulnerability by sending `\r\r\r` as a header block terminator. This can be used for request smuggling with certain proxy servers, such as older versions of Apache Traffic Server and Google Cloud Classic Application Load Balancer, potentially leading to unauthorized access or manipulation of web requests.
- Products
- undertow
- Affected versions
- 1.3.11-1, 1.3.16-1, 1.3.16-1ubuntu0.1~esm1, 1.3.4-1, 1.3.5-1, 1.3.7-1, 1.4.20-1, 1.4.21-1, 1.4.22-1, 1.4.23-1, 1.4.23-2build1, 1.4.23-3, 1.4.23-3ubuntu0.1~esm1, 2.0.23-1, 2.0.27-1, 2.0.28-1, 2.0.29-1, 2.0.29-1ubuntu0.1~esm1, 2.2.12-1, 2.2.13-1, 2.2.14-1, 2.2.16-1, 2.2.16-1ubuntu0.1~esm1, 2.2.8-1, 2.3.18-1, 2.3.18-2, 2.3.20-1, 2.3.20-1ubuntu1, 2.3.8-2, 2.3.8-2ubuntu0.1~esm1
- Fixed versions
- Not specified
- CVEs
- CVE-2026-28367
- Confirmed fixed CVEs
- Not specified
- Updated in this feed
- 31 Oct 2026, 02:06 UTC · Revision 1
Source evidence
A flaw was found in Undertow. A remote attacker can exploit this vulnerability by sending `\r\r\r` as a header block terminator. This can be used for request smuggling with certain proxy servers, such as older versions of Apache Traffic Server and Google Cloud Classic Application Load Balancer, potentially leading to unauthorized access or manipulation of web requests.
osv:UBUNTU-CVE-2026-28367
undertow
Fixed versions: Not specified
undertow
Fixed versions: Not specified
undertow
Fixed versions: Not specified
undertow
Fixed versions: Not specified
undertow
Fixed versions: Not specified
undertow
Fixed versions: Not specified
undertow
Fixed versions: Not specified
undertow
Fixed versions: Not specified
Complete source record
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"modified": "2026-10-17T12:58:08.094652746Z",
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"references": [
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"https://www.cve.org/CVERecord?id=CVE-2026-28367",
"https://bugzilla.redhat.com/show_bug.cgi?id=2443260",
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"published_at": "2026-03-27T17:16:00+00:00"
}