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.
- CVSS 4.0
- 8.3
CVSS:4.0/AV:N/AC:H/AT:N/PR:N/UI:N/VC:N/VI:H/VA:H/SC:N/SI:N/SA:N - CVSS 3.1
- 7.4
CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:H/A:H - EPSS
- 0.6% chance of exploitation in the next 30 days; higher than 48% of CVEs (scores of 2026-10-25)
- CWE
- CWE-787
- Published
- Modified
- Record from
- the NVD, synced
Packages (OSV)
| Advisory | Ecosystem | Package | Affected | Fixed in |
|---|---|---|---|---|
| GHSA-g84c-rxfj-3j2c | npm | webpack-dev-middleware | >=8.0.0 <8.3.0 | 8.3.0 |
| GHSA-g84c-rxfj-3j2c | npm | webpack-dev-middleware | <7.4.6 | 7.4.6 |
References
- https://gist.github.com/thesmartshadow/e0b9481792afb7c31e86fee1ff084490
- https://github.com/madler/zlib
- https://github.com/madler/zlib/blob/v1.3.2/gzwrite.c#L393
- https://github.com/madler/zlib/commit/df84af25dc1942490e1d1c899a07619152a46148
- https://www.vulncheck.com/advisories/zlib-1.3.1.2-through-1.3.2-heap-buffer-overflow-via-gz-vacate