CVE-2026-54466: websocket-driver: Message corruption via abuse of protocol length headers

Should you act?

Critical and remotely reachable

No known exploitation yet, but it is network-reachable without credentials. This signal is computed from CISA KEV, EPSS and CVSS data; it is not an editorial verdict.

• No confirmed exploitation. It is not in CISA’s KEV catalog and CISA’s SSVC assessment records no known exploitation. That can change quickly after a public write-up; re-check if you are affected.
• EPSS 0.4%, percentile 31: FIRST’s model estimates a 0.4% chance of exploitation activity in the next 30 days, higher than 31% of all scored CVEs (low). EPSS is a probability, not a verdict.
• Remotely reachable with no login and no user interaction. If the vulnerable service is exposed to the internet, prioritize it.
• Only applies if your dependency tree includes websocket-driver (npm) < 0.7.5, fixed in 0.7.5. Check your lockfile, including transitive dependencies.

What it is

websocket-driver is a WebSocket protocol handler with pluggable I/O. Prior to 0.7.5, the frame format in draft versions of the WebSocket protocol includes a length header that allows an arbitrarily large integer to be encoded as a sequence of bytes with the high bit set. By sending an indefinite sequence of bytes with values 0x80 or above, a client can make the server parse these bytes into an ever-growing integer in lib/websocket/driver/draft75.js; because JavaScript numbers are 64-bit floating point values, this number will eventually lose precision and lead to the subsequent payload being parsed incorrectly. This issue is fixed in version 0.7.5.

From the GitHub advisory

Impact

The frame format in draft versions of the WebSocket protocol includes a length header that allows an arbitrarily large integer to be encoded as a sequence of bytes with the high bit set. By sending an indefinite sequence of bytes with values 0x80 or above, a client can make the server parse these bytes into an ever-growing integer. Since JavaScript numbers are 64-bit floating point values, this number will eventually lose precision and lead to the subsequent payload being parsed incorrectly.

Patches

The issue has been patched in version 0.7.5 by rejecting the message if the length header exceeds the configured maximum message length. All users should upgrade to this version.

Workarounds

Weakness type: CWE-130.

Product: websocket-driver (npm) · Assigned by: GitHub_M · Published: 2026-07-17

Affected and fixed versions

Severity scores

• Attack vector: network (remotely reachable)
• Attack complexity: low
• Attack requirements: none
• Privileges required: none (no login)
• User interaction: none

CVSS measures how bad a flaw is if exploited, not how likely exploitation is. Read it next to the exploitation data below.

Exploitation and urgency

• CISA KEV: not listed (no confirmed in-the-wild exploitation known to CISA).
• CISA SSVC assessment: exploitation none, automatable yes, technical impact partial.
• FIRST EPSS (model of 2026-10-21): 0.38% probability of exploitation activity in the next 30 days; percentile 31.

Timeline

• 2026-07-15 — GitHub-reviewed advisory GHSA-xv26-6w52-cph6 published (critical)
• 2026-07-17 — CVE record published by GitHub_M
• 2026-07-20 — CVE record last updated

Sources and references

Original sources first. Version and fix details should always be confirmed against the vendor or project advisory.

Vulnerability records

1. GitHub Advisory GHSA-xv26-6w52-cph6 github.com
2. CVE.org record CVE-2026-54466 cve.org
3. NVD entry CVE-2026-54466 nvd.nist.gov

Other references from the CVE record and advisory

1. github.com github.com
2. github.com github.com
3. github.com github.com

Critical npm advisories · Today’s Security Digest