CVE-2026-9675
published 2026-06-17CVE-2026-9675: Impact: The undici WebSocket client enforces maxPayloadSize per-frame but does not enforce the cumulative size of fragmented uncompressed messages. A malicious…
PriorityP345high7.5CVSS 3.1
AVNACLPRNUINSUCNINAH
EPSS
0.43%
34.1th percentile
Impact:
The undici WebSocket client enforces maxPayloadSize per-frame but does not enforce the cumulative size of fragmented uncompressed messages. A malicious WebSocket server can stream many small fragments that each pass per-frame validation but collectively exceed the configured limit, causing unbounded memory growth in the client process. The result is memory exhaustion and a denial of service.
Affected applications are those using the undici WebSocket client (new WebSocket(...)) that can be induced to connect to an attacker-controlled or compromised WebSocket endpoint.
This is a regression specific to undici 8.1.0. The 6.25.0 line shipped the equivalent cumulative check from the start and is unaffected. The 7.x line never had the maxPayloadSize feature and is also unaffected.
Patches:
Upgrade to undici >= 8.5.0.
Workarounds:
No workaround is available. The fix must be applied through an upgrade.
Affected
4 ranges
| Vendor | Product | Version range | Fixed in |
|---|---|---|---|
| ansible-automation-platform | bootc-automation-portal-rhel9 | — | — |
| nodejs | undici | >= 8.0.0 < 8.5.0 | 8.5.0 |
| undici | undici | >= 8.0.0 < 8.5.0 | 8.5.0 |
| undici | undici | >= 8.0.0 < 8.5.0 | 8.5.0 |
CVSS provenance
nvdv3.17.5HIGHCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
cvelistv5v3.17.5HIGHCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
vendor_redhat5.9HIGH
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GHSA
undici WebSocket client vulnerable to denial of service via cumulative fragment bypass
ghsa·2026-06-18
CVE-2026-9675 [HIGH] CWE-400 undici WebSocket client vulnerable to denial of service via cumulative fragment bypass
undici WebSocket client vulnerable to denial of service via cumulative fragment bypass
## Impact
The undici WebSocket client enforces `maxPayloadSize` per-frame but does not enforce the cumulative size of fragmented uncompressed messages. A malicious WebSocket server can stream many small fragments that each pass per-frame validation but collectively exceed the configured limit, causing unbounded memory growth in the client process. The result is memory exhaustion and a denial of service.
Affected applications are those using the undici WebSocket client (`new WebSocket(...)`) that can be induced to connect to an attacker-controlled or compromised WebSocket endpoint.
This is a regression specific to undici 8.1.0. The 6.25.0 line shipped the equivalent cumulative check from the start and
CVEList
undici WebSocket client vulnerable to denial of service via cumulative fragment bypass
cvelistv5·2026-06-17·CVSS 7.5
CVE-2026-9675 [HIGH] CWE-400 undici WebSocket client vulnerable to denial of service via cumulative fragment bypass
undici WebSocket client vulnerable to denial of service via cumulative fragment bypass
Impact:
The undici WebSocket client enforces maxPayloadSize per-frame but does not enforce the cumulative size of fragmented uncompressed messages. A malicious WebSocket server can stream many small fragments that each pass per-frame validation but collectively exceed the configured limit, causing unbounded memory growth in the client process. The result is memory exhaustion and a denial of service.
Affected applications are those using the undici WebSocket client (new WebSocket(...)) that can be induced to connect to an attacker-controlled or compromised WebSocket endpoint.
This is a regression specific to undici 8.1.0. The 6.25.0 line shipped the equivalent cumulative check from the start and is una
VulDB
undici up to 8.4.x maxPayloadSize Feature resource consumption (EUVD-2026-37752)
vuldb·2026-06-17
CVE-2026-9675 [LOW] undici up to 8.4.x maxPayloadSize Feature resource consumption (EUVD-2026-37752)
A vulnerability identified as problematic has been detected in undici up to 8.4.x. This impacts an unknown function of the component maxPayloadSize Feature. This manipulation causes resource consumption.
This vulnerability appears as CVE-2026-9675. The attack may be initiated remotely. There is no available exploit.
You should upgrade the affected component.
Red Hat
undici: undici WebSocket client vulnerable to denial of service via cumulative fragment bypass
vendor_redhat·2026-06-17·CVSS 5.9
CVE-2026-9675 [HIGH] CWE-400 undici: undici WebSocket client vulnerable to denial of service via cumulative fragment bypass
undici: undici WebSocket client vulnerable to denial of service via cumulative fragment bypass
Impact:
The undici WebSocket client enforces maxPayloadSize per-frame but does not enforce the cumulative size of fragmented uncompressed messages. A malicious WebSocket server can stream many small fragments that each pass per-frame validation but collectively exceed the configured limit, causing unbounded memory growth in the client process. The result is memory exhaustion and a denial of service.
Affected applications are those using the undici WebSocket client (new WebSocket(...)) that can be induced to connect to an attacker-controlled or compromised WebSocket endpoint.
This is a regression specific to undici 8.1.0. The 6.25.0 line shipped the equivalent cumulative check from the start and
No detection rules found.
No public exploits indexed.
2026-06-17
Published