Eclipse Vert.x: Request smuggling via canonicalized HTTP/1.x headers
Summary
Eclipse Vert.x, the vertx-core library used for HTTP/1.x processing, misinterprets crafted header names because of a canonicalization step. For example, Content-Xength can be read as Content-Length. A remote attacker can use this to smuggle requests, which can lead to integrity impacts such as manipulated requests or responses. No user interaction or authentication is required, but the attack requires a deployment where a front-end proxy and the Vert.x backend parse headers differently. The CVSS v4.0 base score is 8.7 (High).
Affected
- Eclipse Vert.x 5.0.0 to 5.0.12
- Eclipse Vert.x 5.1.0 to 5.1.9 (GitHub advisory lists 5.1.0 to 5.1.8)
- Eclipse Vert.x 5.2.0 (per CNA record; GitHub advisory lists 5.2.0 as affected)
- Component: io.vertx:vertx-core
Fixed in
- Eclipse Vert.x 5.1.10 (per GitHub advisory)
- Eclipse Vert.x 5.2.1 (per GitHub advisory)
- Fixed version for the 5.0.x line: Unknown.
Workaround
Unknown.
Exploitation
- CISA SSVC: exploitation none, automatable yes, technical impact partial
- Not listed in the CISA KEV catalogue (per OpenCVE)
- EPSS score 0.00274 (per Vulners)
- JFrog has published a technical write-up on desynchronisation and session fixation behind reverse proxies
- Public proof-of-concept code: Unknown.
Our recommendation
- Check whether Eclipse Vert.x versions 5.0.0 to 5.0.12, 5.1.x or 5.2.0 are in use, including as transitive dependencies of io.vertx:vertx-core.
- Upgrade to 5.1.10 or 5.2.1 or later. For the 5.0.x line, check the vendor advisory for a fixed version.
- Until patched, make sure the Vert.x service is reachable only through the front-end proxy and that proxy and backend parse framing headers consistently.
- Monitor for signs of request smuggling, such as unexpected responses or responses intended for other users.
Public exploits
PoC-in-GitHub, Metasploit and Exploit-DB list nothing for this CVE.
Research sources
- GitHub Security Advisory GHSA-ch7p-g5pm-3gqx github.com
- Eclipse Foundation CVE assignment work item #352 gitlab.eclipse.org
- oss-security mailing list post www.openwall.com
- JFrog research: header typo session fixation research.jfrog.com
- OpenCVE CVE-2026-102479 app.opencve.io
- Vulners CVE-2026-102479 vulners.com
Researched and written up in English and German by an AI (Claude by Anthropic) based on NVD, CISA, EPSS and the sources listed. The vendor information is authoritative. Researched on 1 Nov 2026, 02:47.
Original description (NVD)
In Eclipse Vert.x versions [5.0.0,5.0.12] or [5.1.0,5.1.9] or [5.2.0, 5.2.0], the Vert.x HTTP/1.x decoder uses a canonicalization for well known HTTP headers, the canonicalization process interprets well crafted headers as headers of this list, allowing for instance Content-Xength to be interpeted as Content-Length. This can be exploited for request smuggling purpose. The impacted component is io.vertx:vertx-core.
Sources
The tracker combines official, freely usable data sources – updated continuously:
- NVD (NIST) – CVEs, rating (CVSS), affected products
- CISA KEV – vulnerabilities confirmed by CISA as actively exploited
- CISA Vulnrichment – CISA assessment (SSVC) in the official CVE record
- FIRST EPSS – probability of exploitation
- Microsoft MSRC – Patch Tuesday: vulnerabilities, severity, updates
- PoC-in-GitHub – public proof-of-concept repositories
- Metasploit (Rapid7) – modules of the Metasploit Framework
- Exploit-DB (OffSec) – archive of public exploits (links only)
- Patch days: official vendor pages (linked per vendor) (Vendor patch days)
This product uses data from the NVD API but is not endorsed or certified by the NVD. EPSS data © FIRST.org.
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