CVE-2026-1526 is a high-severity security vulnerability in undici (npm), affecting versions < 6.24.0. It is fixed in 6.24.0, 7.24.0.
Description The undici WebSocket client is vulnerable to a denial-of-service attack via unbounded memory consumption during permessage-deflate decompression. When a WebSocket connection negotiates the permessage-deflate extension, the client decompresses incoming compressed frames without enforcing any limit on the decompressed data size. A malicious WebSocket server can send a small compressed frame (a "decompression bomb") that expands to an extremely large size in memory, causing the Node.js process to exhaust available memory and crash or become unresponsive. The vulnerability exists in the PerMessageDeflate.decompress() method, which accumulates all decompressed chunks in memory and concatenates them into a single Buffer without checking whether the total size exceeds a safe threshold. Impact Remote denial of service against any Node.js application using undici's WebSocket client A single compressed WebSocket frame of ~6 MB can decompress to ~1 GB or more Memory exhaustion occurs in native/external memory, bypassing V8 heap limits No application-level mitigation is possible as decompression occurs before message delivery Patches Users should upgrade to fixed versions. Workarounds No workaround are possible.
CVE-2026-1526 has a CVSS score of 7.5 (High). The vector is network-reachable, no privileges required, and no user interaction. A CVSS score reflects the worst-case severity of the vulnerability, not your specific exposure. Whether this affects your application depends on whether the vulnerable code is present and reachable in your environment.
A fixed version is available (6.24.0, 7.24.0). Upgrading removes the vulnerable code path.
npm
undici (< 6.24.0)undici (>= 7.0.0, < 7.24.0)undici → 6.24.0 (npm)undici → 7.24.0 (npm)Severity tells you how bad this could be in the worst case. It does not tell you whether you are exposed. Exploitability and impact are functions of runtime truth: whether the vulnerable code is present, reachable, and actually executes in your application. A vulnerable package can sit in your dependency tree and never run.
Kodem, an Intelligent Application Security platform, uses runtime intelligence to reveal which vulnerabilities actually execute in production, so teams prioritize the ones that genuinely matter instead of chasing every advisory.
Kodem's runtime-powered SCA identifies whether CVE-2026-1526 is reachable in your applications. Explore open-source security for your team.
See if CVE-2026-1526 is reachable in your applications. Get a demo
Upgrade the following packages to resolve this vulnerability:
undici to 6.24.0 or laterundici to 7.24.0 or laterKodem Kai can prioritize this vulnerability in your dependency tree and generate a fix recommendation.
CVE-2026-1526 is a high-severity security vulnerability in undici (npm), affecting versions < 6.24.0. It is fixed in 6.24.0, 7.24.0.
CVE-2026-1526 has a CVSS score of 7.5 (High). This score reflects the worst-case severity of the vulnerability, not your specific exposure. Whether it represents real risk in your environment depends on whether the vulnerable code is present and reachable.
undici (npm) versions < 6.24.0 is affected.
Yes. CVE-2026-1526 is fixed in 6.24.0, 7.24.0. Upgrade to this version or later.
Whether CVE-2026-1526 is exploitable in your environment depends on whether the vulnerable code is present and reachable. A CVSS score is a worst-case rating; it does not account for your specific deployment, configuration, or usage patterns. Kodem, an Intelligent Application Security platform, uses runtime intelligence to show which vulnerabilities actually execute in production, so you can focus on the ones that represent real risk. Get a demo
Exploitability and impact are not fixed properties of a CVE. They depend on runtime truth: whether the vulnerable code is present, reachable, and actually executes in your application. A high CVSS score on a dependency that never runs is not the same as real risk. Kodem, an Intelligent Application Security platform, uses runtime intelligence to reveal which vulnerabilities actually execute in production, so teams prioritize the ones that genuinely matter.
undici to 6.24.0 or laterundici to 7.24.0 or later