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.

Affected: npm: webpack-dev-middleware

> [!IMPORTANT] > CVE-2026-76844 was assigned and published for this issue by VulnCheck on 2026-08-24 without prior coordination with the webpack maintainers or the OpenJS Foundation, which holds the CVE Numbering Authority scope for webpack projects. Neither the maintainers nor the OpenJS CNA were notified before publication, and no fix was available at that time. This advisory is the coordinated record produced by the webpack maintainers and the OpenJS Foundation CNA.

### Impact

`webpack-dev-middleware` resolves a request to a local file in `getFilenameFromUrl`. When the configured `publicPath` has no trailing slash (for example `/assets`), a request that shares that prefix without being under it (for example `/assets../secret`) still passes the containment check, and the `..` guard does not catch it because it runs on the path before the `publicPath` prefix is stripped. The stripped remainder then escapes the configured output directory once joined, so an unauthenticated request can read files outside the output root. Applications serving `webpack-dev-middleware` (directly or via `webpack-dev-server`) with a `publicPath` that does not end in a slash are affected. A development server reachable on the network can be attacked with a single request and no victim interaction.

### Patches

Patched in `webpack-dev-middleware` 8.3.0. There is no backport to the 5.x, 6.x, or 7.x lines; users on those lines should upgrade to 8.3.0 or later.

### Workarounds

Configure `publicPat…

webpack-dev-middleware: lack of URL validation may lead to file leak curl: curl: Authentication bypass due to incorrect connection reuse with Negotiate authentication curl: curl: Information disclosure via OAuth2 bearer token leakage during HTTP(S) redirect tar: tar: Hidden file injection via crafted archives fast-uri: fast-uri: URI authority bypass due to improper delimiter handling libxml2: mingw-libxml2: libxml2: Denial of Service via crafted XML input due to use-after-free curl: curl: Insecure connection establishment due to TLS configuration mismatch curl: curl: Man-in-the-middle attack via SSH host key bypass sqlite: SQLite: Arbitrary code execution via crafted FTS5 full-text search data sqlite: SQLite: Arbitrary code execution and crash via heap-based buffer overflow in FTS5 libxml2: libxml2: Arbitrary code execution in xmlcatalog utility via buffer overflow libarchive: Double-Free Vulnerability in RAR5 Decompression Logic via dangling filtered_buf pointer in init_unpack() GDBusServer: glib2: GDBusServer pre-authentication DoS via unbounded SASL line buffering tar: tar: TOCTOU in incremental dumpdir 'X' rename handling allows restore path escape tar: tar: --one-top-level hardlink targets not confined to top-level directory enabling arbitrary file overwrite gzip: gzip: Arbitrary file overwrite via insecure temporary file handling in gzexe utility gzip: gzip: Information disclosure via global buffer overflow in LZH decompression python-idna: idna: Denial of Service via…