CVE-2026-21435 json
webtransport-go CloseWithError can block indefinitely
published 2026-02-12 8 mo ago modified 2026-09-10 1 mo ago also GHSA-px4r-g4p3-hhqv , GO-2026-4488 , EUVD-2026-6717
- cvss
- 5.3
- version 3.1, CNA
- cisa kev
- Not listed
- not in CISA's catalog
- epss
- 0.5%
- EPSS 0.5% chance of exploitation in 30 days, percentile 39%
- public exploits
- 0
- none known
Summary
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.
Patch / fix
- go github.com/quic-go/webtransport-go 0.10.0
- quic-go webtransport-go 0.10.0
- govulncheck-vulndb openSUSE Leap 15.6 0.0.20260226T182644-150000.1.149.1
suse advisories SUSE-SU-2026:0757-1
- govulncheck-vulndb openSUSE Leap 16.0 0.0.20260723T184607-160000.1.1
opensuse advisories openSUSE-SU-2026:21483-1
CISA SSVC
- Exploitation
- none
- Automatable
- yes
- Technical impact
- partial
- Assessed
- 8 mo ago
Exploit prediction
0.46% chance of exploitation in the next 30 days, higher than 39% of all scored CVEs (FIRST EPSS, 2026-11-08).
CVSS scores
| assigned by | version | score | vector |
|---|---|---|---|
| CNA | 3.1 | 5.3 | CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L |
| NVD | 3.1 | 7.5 | CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H |
| GitHub | 3.1 | 5.3 | CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L |
Affected packages
| ecosystem | package | affected | fixed in |
|---|---|---|---|
| go | github.com/quic-go/webtransport-go | <0.10.0 |
0.10.0 |
Affected products
- quic-go webtransport-go
Classification
- Weakness
-
- CWE-400 Uncontrolled Resource Consumption
References
-
github.com
/quic-go/webtransport-go/security/advisories/GHSA-px4r-g4p3-hhqv
web, vendor-advisory, advisory
-
github.com
/quic-go/webtransport-go/releases/tag/v0.10.0
web, product, release-notes
-
nvd.nist.gov
/vuln/detail/CVE-2026-21435
advisory
-
github.com
/quic-go/webtransport-go
package
Sources
- CVE List CVE-2026-21435
- GitHub Advisory GHSA-px4r-g4p3-hhqv
- NVD CVE-2026-21435
- OSV GO-2026-4488
Fencer Vulns keeps one entry per vulnerability: the CVE id wins, then GHSA, and records that alias each other are merged, except that two CVEs always keep separate entries. The same data is available as JSON.