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CVE-2026-21438

20
FAUCET Score

CVE-2026-21438 affects webtransport-go and quic-go, where an attacker can trigger unbounded memory consumption by repeatedly creating and closing WebTransport streams. This medium-severity vulnerability (CVSS 5.3) has a low attack complexity and requires no user interaction, potentially leading to denial of service due to resource exhaustion. There is currently no evidence of active exploitation, no public exploit code available, and minimal community discussion or media coverage beyond a single security update notice.

Impacted Technologies

VendorProductVersion(s)CPE
< 0.10.0CPE matchmatch criteria
cpe:2.3:a:quic-go:webtransport-go:*:*:*:*:*:go:*:*

CVSS Data

CVSS version used by this source: 3.1

5.3MEDIUM

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

Attack Vector
NETWORK
Attack Complexity
LOW
Privileges Required
NONE
User Interaction
NONE
Scope
UNCHANGED
Confidentiality Impact
NONE
Integrity Impact
NONE
Availability Impact
LOW
Exploitability Score
3.9
Impact Score
1.4
CvssVersion
3.1

Exploit Intelligence

EPSS Score
0.37%
Probability of exploitation in next 30 days
EPSS Percentile
29.2%
Percentile rank of EPSS score among Peer Group
As of 2026-07-27
Model: v2026.06.15
This CVE's current EPSS score of 0.0037 is in the 18th percentile among its peer group of 23,723 CVEs.

Social Chatter

The average CVE in this peer group has 0.0 Twitter, 0.0 Reddit, 0.1 Bluesky, 0.0 Mastodon, and 0.4 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 (2)

gopatch availablevia ghsa
Product: github.com/quic-go/webtransport-goFixed in: 0.10.0
github_advisoryvendor investigatingvia nvd_reference
View patch

Vendor Advisories (1)

goGHSA-2f2x-8mwp-p2gcmedium

webtransport-go: Memory Exhaustion Attack due to Missing Cleanup of Streams Map

Feb 12, 2026

References

github.com / quic-go/webtransport-go/releases/tag/v0.10.0
ProductRelease Notes
github.com / quic-go/webtransport-go/security/advisories/GHSA-2f2x-8mwp-p2gc
Vendor Advisory