CVE-2023-40167: Jetty accepts "+" prefixed value in Content-Length

Severity: medium (CVSS 5.3 v3.1)
Exploited in the wild: not listed in CISA KEV
EPSS: 1.3% probability of exploitation in the next 30 days
Public exploit or detection template: none known
Published: 2023-09-15 · updated 2026-06-17
Weakness: CWE-130

Description

Jetty is a Java based web server and servlet engine. Prior to versions 9.4.52, 10.0.16, 11.0.16, and 12.0.1, Jetty accepts the `+` character proceeding the content-length value in a HTTP/1 header field. This is more permissive than allowed by the RFC and other servers routinely reject such requests with 400 responses. There is no known exploit scenario, but it is conceivable that request smuggling could result if jetty is used in combination with a server that does not close the connection after sending such a 400 response. Versions 9.4.52, 10.0.16, 11.0.16, and 12.0.1 contain a patch for this issue. There is no workaround as there is no known exploit scenario.

Affected products

Debian Linux: 10.0, 11.0, 12.0
The Eclipse Foundation Eclipse Jetty: from 9.0.0 before 9.4.52; from 10.0.0 before 10.0.16; from 11.0.0 before 11.0.16; 12.0.0, 12.0.0-beta0, 12.0.0-beta1, 12.0.0-beta2, 12.0.0-beta3, 12.0.0-beta4 — fixed in 10.0.16, 11.0.16, 9.4.52

How to fix

Upgrade to a fixed version: The Eclipse Foundation Eclipse Jetty 10.0.16, 11.0.16, 9.4.52. Check the vendor advisory for mitigations.

References

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