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© 2026 FAUCET Technologies LLC. All rights reserved.

CVE-2023-48230

28
FAUCET Score

CVE-2023-48230 is a critical buffer underrun vulnerability affecting Cap'n Proto versions 1.0 and 1.0.1 when using the KJ HTTP library with WebSocket compression enabled. A remote attacker can trigger a crash, leading to a denial-of-service, and potentially remote code execution, though the latter is considered less likely due to the non-attacker-controlled write. Rated with a CVSS score of 9.8 (CRITICAL), this vulnerability has a low attack complexity and requires no user interaction, making it easily exploitable over the network. The primary impact is denial-of-service, but the possibility of remote code execution cannot be entirely ruled out. Currently, there is no evidence of active exploitation, public exploit code (Metasploit, Nuclei, ExploitDB), or significant community discussion surrounding this vulnerability. The maintainers suspect only the Cloudflare Workers Runtime is affected, and the issue is resolved in Cap'n Proto 1.0.1.1.

Impacted Technologies

VendorProductVersion(s)CPE
1.0.0CPE matchmatch criteria
cpe:2.3:a:capnproto:capnproto:1.0.0:*:*:*:*:*:*:*
1.0.1CPE matchmatch criteria
cpe:2.3:a:capnproto:capnproto:1.0.1:*:*:*:*:*:*:*

CVSS Data

CVSS version used by this source: 3.1

5.9MEDIUM

CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:H

Attack Vector
NETWORK
Attack Complexity
HIGH
Privileges Required
NONE
User Interaction
NONE
Scope
UNCHANGED
Confidentiality Impact
NONE
Integrity Impact
NONE
Availability Impact
HIGH
Exploitability Score
2.2
Impact Score
3.6
CvssVersion
3.1

Exploit Intelligence

EPSS Score
1.89%
Probability of exploitation in next 30 days
EPSS Percentile
77.4%
Percentile rank of EPSS score among Peer Group
As of 2026-07-27
Model: v2026.06.15
This CVE's current EPSS score of 0.0189 is in the 66th percentile among its peer group of 36,862 CVEs.

Social Chatter

The average CVE in this peer group has 0.0 Twitter, 0.1 Reddit, 0.3 Bluesky, 0.3 Mastodon, and 2.4 GitHub mentions.

Media Mentions

No media coverage found for this CVE.

The average CVE in this peer group has 0.3 InfoSec Media, 0.0 Vendor Blog, and 0.0 Security Researcher mentions.

Remediation

Patch Available

Vendor Patches (1)

github_advisorypatch availablevia nvd_reference
View patch

References

github.com / capnproto/capnproto/commit/75c5c1499aa6e7690b741204ff9af91cce526c59
Patch
github.com / capnproto/capnproto/commit/e7f22da9c01286a2b0e1e5fbdf3ec9ab3aa128ff
Patch
github.com / capnproto/capnproto/security/advisories/GHSA-r89h-f468-62w3
ExploitPatchVendor Advisory