7.5

CVE-2026-21435: webtransport-go CloseWithError can block indefinitely

Analyzed
AliasesCGA-2467-r4w6-fvgjCGA-2hg7-hqxg-h8mvCGA-32j9-5jwf-w4c8
Published 12-02-2026Last modified 17-02-2026

Vulnerability summary

CVE-2026-21435 is a high (CVSS 7.5) Uncontrolled Resource Consumption vulnerability in quic-go webtransport-go. EPSS estimates a 0.46% chance of exploitation in the next 30 days, higher than 40.3% of scored vulnerabilities.

Priority
Routine

Not severe (CVSS 5.3, network access); no exploitation reported by the 5 checked sources

Source freshness unavailable

How is this decided?
CVSS score
7.5/10
010
High · v3.1 (NVD)
EPSS score
0.46%
0%100%
Low · +0.03 pp in 30 days
KEVNot listedNot listed by any tracked catalog.
RansomwareNot flaggedNo ransomware use recorded.
Public exploits0No public exploits recorded

Advisory lineage

Upstream 0 · Downstream 2 · Related 3
OPENSUSE-SU-2026:21483-1SUSE-SU-2026:0757-1CGA-CJ6M-9RXM-V36R

Timeline

  1. 12-02-2026
    PublishedVulnerability first disclosed.
  2. 17-02-2026
    Last modifiedVulnerability information updated.

Description

webtransport-go is an implementation of the WebTransport protocol. Prior to v0.10.0, an attacker can cause a denial of service in webtransport-go by preventing or indefinitely delaying WebTransport session closure. A malicious peer can withhold QUIC flow control credit on the CONNECT stream, blocking transmission of the WT_CLOSE_SESSION capsule and causing the close operation to hang. This vulnerability is fixed in v0.10.0.

CVSS metrics

5 scores · 5 sources · 1 version

EPSS trend

Probability

0.46%

Chance of exploitation in the next 30 days

Percentile

40%

Versus all other CVEs

30-day change

Increase +0.03 pp

From 0.44% on 04-10-2026

04-10-202603-11-2026

Known exploited

Compare KEV catalogs
CISA KEV

Not in the CISA KEV catalog.

ENISA CNW

Not in the ENISA CNW catalog.

CIRCL

Not in the CIRCL catalog.

Public exploits

0 found

No public exploits indexed.

Weaknesses

CWE · root cause

Affected systems

Version check

Known conditions: network-reachable, no authentication, no user interaction (CVSS vector). Other conditions: not stated in public data.

Chainguard18 products
  • ipfs-cluster< 1.1.5-r5
  • ipfs-cluster-fips< 1.1.5-r4
  • k3s< 1.35.1.1-r1
  • k3s-1.31< 1.31.6.1-r13
  • k3s-1.32< 1.32.13.1-r2
Wolfi9 products
  • ipfs-cluster< 1.1.5-r5
  • k3s< 1.35.1.1-r1
  • k3s-1.32< 1.32.13.1-r2
  • k3s-1.33< 1.33.9.1-r3
  • k3s-static< 1.35.1.1-r1
Github.com/quic-go1 product
  • webtransport-go< 0.10.0
Quic-go1 product

4 vendors · 29 products

References

5 links