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© 2026 FAUCET Technologies LLC. All rights reserved.

CVE-2026-58055

29
FAUCET Score

nghttp2's nghttpx proxy through 1.69.0 forwards an HTTP/1.1 Upgrade request that also carries a Content-Length header and body onto reusable keep-alive backend connections, re-adding the Upgrade and Connection headers while passing Content-Length verbatim. A backend that resolves the resulting ambiguous message in the attacker's favor enables HTTP request/response smuggling and cross-client response-queue poisoning.

First published: Jun 28, 2026Last modified: Jun 29, 2026

Impacted Technologies

VendorProductVersion(s)CPE
<= 1.69.0CPE matchmatch criteria
cpe:2.3:a:nghttp2:nghttp2:*:*:*:*:*:*:*:*
>= 0, <= 1.69.0CPE match
cpe:2.3:a:nghttp2:nghttp2:*:*:*:*:*:*:*:*

CVSS Data

CVSS version used by this source: 4.0

6.3MEDIUM

CVSS:4.0/AV:N/AC:H/AT:N/PR:N/UI:N/VC:L/VI:L/VA:N/SC:N/SI:L/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X

Attack Vector
NETWORK
Attack Complexity
HIGH
Attack Requirements
NONE
Privileges Required
NONE
User Interaction
NONE
VS Confidentiality
LOW
VS Integrity
LOW
VS Availability
NONE
SS Confidentiality
NONE
SS Integrity
LOW
SS Availability
NONE
Exploit Maturity
NOT_DEFINED
CvssVersion
4.0

Exploit Intelligence

EPSS Score
0.20%
Probability of exploitation in next 30 days
EPSS Percentile
10.4%
Percentile rank of EPSS score among Peer Group
As of 2026-07-27
Model: v2026.06.15
This CVE's current EPSS score of 0.0020 is in the 1st percentile among its peer group of 19,958 CVEs.

Social Chatter

The average CVE in this peer group has 0.0 Twitter, 0.0 Reddit, 0.0 Bluesky, 0.0 Mastodon, and 0.2 GitHub mentions.

Media Mentions

The average CVE in this peer group has 0.0 InfoSec Media, 0.0 Vendor Blog, and 0.0 Security Researcher mentions.

Remediation

Patch Available

Vendor Patches (4)

ubuntupatch availablevia ubuntu_usn
Product: nghttp2 (jammy)Fixed in: 1.43.0-1ubuntu0.4
ubuntupatch availablevia ubuntu_usn
Product: nghttp2 (noble)Fixed in: 1.59.0-1ubuntu0.4
ubuntupatch availablevia ubuntu_usn
Product: nghttp2 (questing)Fixed in: 1.64.0-1.1ubuntu1.2
ubuntupatch availablevia ubuntu_usn
Product: nghttp2 (resolute)Fixed in: 1.68.0-2ubuntu0.2

Vendor Advisories (2)

ubuntuUSN-8495-1

nghttp2 vulnerability

Jul 2, 2026
microsoft2026-Jun/CVE-2026-58055Moderate

nghttp2 nghttpx - HTTP Request/Response Smuggling via Upgrade Request with Content-Length

Jun 9, 2026

References

github.com / bikini/exploitarium/tree/main/nghttp2-nghttpx-upgrade-queue-poison-poc
Broken Link
github.com / nghttp2/nghttp2/commit/ab28105c4a0197da24f8bfc414bc116055249e1e
Patch
vulncheck.com / advisories/nghttp2-nghttpx-http-request-response-smuggling-via-upgrade-request-with-content-length
PatchThird Party Advisory