GHSA-vrm6-8vpv-qv8q CVE-2026-1526
Undici has Unbounded Memory Consumption in WebSocket permessage-deflate Decompression
- Severity
- 7.5 / 10
- High · CVSS 3.1
- Exploit chance (EPSS)
- 1.20%
- Chance of exploitation in the next 30 days. Higher than 68.10% of scored vulnerabilities.
- Known exploited
- No
- Not in CISA's catalog
- Weakness
- CWE-409 Improper Handling of Highly Compressed Data (Data Amplification)
- Fix
6.24.0- Upgrade undici to this version or later
Description
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.
Affected versions
npm
| Package | Vulnerable | Fixed in |
|---|---|---|
| undici | < 6.24.0 |
6.24.0 |
| undici | >= 7.0.0, < 7.24.0 |
7.24.0 |
| undici | < 6.24.0 |
6.24.0 |
| undici | >= 7.0.0, < 7.24.0 |
7.24.0 |
How to fix
Move to the fixed version or later with your package manager, update the lockfile, and run your tests. If the package only arrives through another dependency, upgrade that dependency first. If none of its releases pulls a fixed version yet, force the version with your package manager's override.
undici npm → 6.24.0
- npm
npm install undici@6.24.0- yarn
yarn add undici@6.24.0- pnpm
pnpm add undici@6.24.0
Severity breakdown
CVSS 3.1 7.5
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
- Attack vector
- Network
- Attack complexity
- Low
- Privileges required
- None
- User interaction
- None
- Scope
- Unchanged
- Confidentiality
- None
- Integrity
- None
- Availability
- High
Weakness
CWE-409: Improper Handling of Highly Compressed Data (Data Amplification)
The product does not handle or incorrectly handles a compressed input with a very high compression ratio that produces a large output.
References
Advisories
Packages
Other links
- hackerone.com/reports/3481206
- cna.openjsf.org/security-advisories.html
- datatracker.ietf.org/doc/html/rfc7692
- owasp.org/www-community/attacks/Denial_of_Service
- access.redhat.com/errata/RHSA-2026:13826
- access.redhat.com/errata/RHSA-2026:17789
- access.redhat.com/errata/RHSA-2026:21772
- access.redhat.com/errata/RHSA-2026:21931
- access.redhat.com/errata/RHSA-2026:34342
- access.redhat.com/errata/RHSA-2026:56431
- access.redhat.com/errata/RHSA-2026:5807
- access.redhat.com/errata/RHSA-2026:7080
- access.redhat.com/errata/RHSA-2026:7123
- access.redhat.com/errata/RHSA-2026:7302
- access.redhat.com/errata/RHSA-2026:7310
- access.redhat.com/errata/RHSA-2026:7350
- access.redhat.com/errata/RHSA-2026:7670
- access.redhat.com/errata/RHSA-2026:7675
- access.redhat.com/errata/RHSA-2026:7983
- access.redhat.com/errata/RHSA-2026:9742
- access.redhat.com/security/cve/CVE-2026-1526
- bugzilla.redhat.com/show_bug.cgi
- security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-1526.json
Timeline
- Published
- Last updated by the source
- Latest EPSS score
Related advisories
| Advisory | Severity | Why it's related |
|---|---|---|
| GHSA-55wc-3pg8-jfw6 undici vulnerable to Denial of Service via unhandled exception in the decompress interceptor | High | Also affects undici |
| GHSA-qrxm-fqhp-jwvm undici vulnerable to Denial of Service via TLS 1.2 certificate-changing renegotiation | High | Also affects undici |
| GHSA-9fm3-97px-rjf6 undici WebSocket client vulnerable to Denial of Service via unbounded automatic PONG buffering | High | Also affects undici |
| GHSA-4qv8-2p9j-2685 undici vulnerable to Denial of Service via unbounded memory in the EventSource parser | High | Also affects undici |
| GHSA-xjj6-f33q-929c undici vulnerable to Denial of Service via unhandled error on excessive content-encodings | High | Also affects undici |
| GHSA-f72v-6w45-q472 undici vulnerable to Subresource Integrity bypass via non-lowercase algorithm tokens | High | Also affects undici |
| GHSA-4w7w-5xrc-9h26 undici vulnerable to cache poisoning and cross-user disclosure via cross-origin redirects | Critical | Also affects undici |
| GHSA-2m5v-pch6-74hx undici vulnerable to TLS certificate validation bypass via dropped tls options in Agent | Critical | Also affects undici |
Credits: HO-9, UlisesGascon, mcollina
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