How severe is CVE-2023-38697?

CVE-2023-38697 has a CVSS score of 5.8/10, rated MEDIUM. Review your exposure and patch according to your risk tolerance.

Which packages are affected by CVE-2023-38697?

CVE-2023-38697 affects the following packages: protocol-http1 (RubyGems). Ecosystems affected: RubyGems.

How do I fix CVE-2023-38697?

Update protocol-http1 to 0.15.1 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2023-38697 is resolved across your whole dependency graph.

How do I detect CVE-2023-38697 in my RubyGems dependencies?

Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for protocol-http1, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.

How do I mitigate CVE-2023-38697 if there is no patch (or I can't update yet)?

If you can't upgrade right away: gate or disable the affected feature, validate untrusted input at the boundary, and avoid passing attacker-controlled data into the vulnerable path. O3's runtime protection blocks exploitation in production as an interim safeguard until the upgrade lands.

Is CVE-2023-38697 actively exploited in the wild?

No public exploit code has been indexed for CVE-2023-38697 yet. This does not mean the vulnerability cannot be exploited — absence of public exploits does not imply safety. Apply the recommended fix and use O3 Security to monitor your exposure.

What is the EPSS score for CVE-2023-38697?

CVE-2023-38697 has an EPSS (Exploit Prediction Scoring System) score of 0.8%, placing it in the 55th percentile of all CVEs. EPSS is maintained by FIRST.org and estimates the probability that a vulnerability will be exploited in the wild within the next 30 days. This score indicates relatively lower exploitation probability, though the CVSS severity should still guide your patching priority.

What type of vulnerability is CVE-2023-38697?

CVE-2023-38697 is classified as CWE-444 (CWE-444). This weakness type describe the underlying flaw category, which helps determine the potential impact and the right class of mitigation.

When was CVE-2023-38697 published, and has it been updated?

CVE-2023-38697 was published on August 4, 2023 and was last updated on October 28, 2026. Advisory data evolves as severity scores, affected ranges, and exploit intelligence are revised — always check the latest version of the advisory before acting.

💎

💎 RubyGems

Not in CISA KEV

MEDIUM severity

CVE-2023-38697 — protocol-http1

MEDIUMFix: socketry/protocol-http1@e11fc16

CVE-2023-38697 is a medium-severity (CVSS 5.8) CWE-444 vulnerability in protocol-http1. A fix is available for protocol-http1 — see the affected versions and patch details below.

protocol-http1 HTTP Request/Response Smuggling vulnerability

Also known asGHSA-6jwc-qr2q-7xwj

Published

Aug 4, 2023

Updated

Oct 28, 2026

Affected

1 pkg

Patched

1 / 1

Exploits

None indexed

Exploitation data as of Nov 8, 2026 · OSV.dev, NVD, FIRST.org (EPSS)

Exploitation Status

No confirmed exploitation observed yet

CISA assesses this as automatable — exploitation doesn’t require manual, per-target effort, which raises the odds of mass scanning and opportunistic attacks.
CISA’s own triage has not observed active exploitation or public proof-of-concept code for this CVE as of its last assessment.

Exploitation and automatability from CISA’s SSVC triage for CVE-2023-38697.

EPSS Exploitation Probability

via FIRST.org ↗

0.8%probability of exploitation in next 30 days

Lower Risk0.00%

Lower risk than most CVEs55th percentile — riskier than 55% of all scored CVEsHighest risk

Probability of exploitation in the next 30 days, from FIRST.org EPSS.

How urgent is this, really

Where this sits among everything scored

Real-World Exposure

1 pkg affected

💎protocol-http1

Real-time download stats are indexed for npm and PyPI packages. This vulnerability affects RubyGems packages — download data is not available via public APIs for these ecosystems.

Description

Impact

RFC 9112 Section 7.1 defined the format of chunk size, chunk data and chunk extension (detailed ABNF is in Appendix section).

In summary:

The value of Content-Length header should be a string of 0-9 digits.
The chunk size should be a string of hex digits and should split from chunk data using CRLF.
The chunk extension shouldn't contain any invisible character.

However, we found that Falcon has following behaviors while disobey the corresponding RFCs.

Falcon accepts Content-Length header values that have "+" prefix.
Falcon accepts Content-Length header values that written in hexadecimal with "0x" prefix.
Falcon accepts "0x" and "+" prefixed chunk size.
Falcon accepts LF in chunk extension.

This behavior can lead to desync when forwarding through multiple HTTP parsers, potentially results in HTTP request smuggling and firewall bypassing. Note that while these issues were reproduced in Falcon (the server), the issue is with protocol-http1 which implements the HTTP/1 protocol parser. We have not yet been advised of any real world exploit or practical attack.

Patches

Fixed in protocol-http1 v0.15.1+.

Workarounds

None.

References

https://github.com/socketry/protocol-http1/pull/20

Affected Packages

1 total 1 fixed

Ecosystem	Package	Vulnerable range	Fix
💎RubyGems	`protocol-http1`	all versions	0.15.1`bundle update protocol-http1 --conservative`

Affected Products

1 product · 1 configurations

Application

protocol-http1socketry

< 0.15.1

range

Detection & mitigation playbook

Open-source dependency

Detect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for protocol-http1, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.
Fix
Update protocol-http1 to 0.15.1 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2023-38697 is resolved across your whole dependency graph.
Workarounds
If you can't upgrade right away: gate or disable the affected feature, validate untrusted input at the boundary, and avoid passing attacker-controlled data into the vulnerable path. O3's runtime protection blocks exploitation in production as an interim safeguard until the upgrade lands.

Frequently Asked Questions

### Impact [RFC 9112 Section 7.1](https://www.rfc-editor.org/rfc/rfc9112#name-chunked-transfer-coding) defined the format of chunk size, chunk data and chunk extension (detailed ABNF is in Appendix section). In summary: - The value of Content-Length header should be a string of 0-9 digits. - The chunk size should be a string of hex digits and should split from chunk data using CRLF. - The chunk extension shouldn't contain any invisible character. However, we found that Falcon has following behaviors while disobey the corresponding RFCs. - Falcon accepts Content-Length header values that h