Buffer overflow in Webpack Webpack-Dev-Middleware
CVE-2026-76844
zlib 1.2.11 through 1.3.2 contains a heap buffer overflow: after an underlying write() fails, gz_write() returns without resetting strm.next_in, leaving it pointed at the caller's buffer. A later gz* write call then derives a position from the stale pointer and writes past a heap allocation; any write() failure reaches it, including EPIPE on a blocking descriptor, and in versions before 1.3.1.2 the failed write must be followed by a gzclearerr() call.
Vulnerability class: Buffer Overflow
Published · last modified .
CVSS v3 metric
CVSS v3 base score 7.4 (High). Vector: CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:H/A:H.
EPSS exploit prediction
EPSS: 0.006 (46.6th percentile), scored .
Very low probability of exploitation in the next 30 days; routine patching cadence is appropriate. 47th percentile — 46.6% of CVEs in the catalogue have a lower EPSS than this one. How to read EPSS.
EPSS over last 30 days · oldest: 0.004 · newest: 0.006 · change: +0.002
Affected products
Weakness classification (CWE)
References
- github.com/webpack/webpack-dev-middleware (product)
- github.com/webpack/webpack-dev-middleware/blob/v8.1.1/src/middleware.js (technical-description)
- github.com/advisories/GHSA-wr3j-pwj9-hqq6 (related)
- www.vulncheck.com/advisories/webpack-dev-middleware-path-traversal-via-offset-s… (third-party-advisory)
- github.com/webpack/webpack-dev-middleware/security/advisories/GHSA-g84c-rxfj-3j… (vendor-advisory)
- github.com/webpack/webpack-dev-middleware/commit/13344e78b26d88fe9b7c8381a3860e… (patch)
- github.com/webpack/webpack-dev-middleware/commit/cefccbac330c29052fc6dffe85fd29… (patch)
- github.com/webpack/webpack-dev-middleware/releases/tag/v8.3.0 (release-notes)
- github.com/webpack/webpack-dev-middleware/releases/tag/v7.4.6 (release-notes)
- gist.github.com/thesmartshadow/e0b9481792afb7c31e86fee1ff084490 (technical-description, exploit)
Frequently asked questions
- What is CVE-2026-76844?
- CVE-2026-76844 is a high-severity vulnerability in Webpack Webpack-Dev-Middleware, classified under Out-of-bounds Write. CVSS score: 7.4/10. Published 2026-08-24.
- How severe is CVE-2026-76844?
- High severity. CVSS v3 base score is 7.4 out of 10.