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CVE-2026-76844

high CVSS 7.4 EPSS 0.6%

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.

Versions it affects

Software versions checked with the free lookup that CVE-2026-76844 applies to, and the release that fixes it where the sources name one.

zlib 1.2.11

At a glance

Severity
High
CVSS base score
7.4 out of 10
Known exploited
Not in CISA's catalogue of exploited vulnerabilities
EPSS
0.6% probability of exploitation in the next 30 days, higher than 47% of scored vulnerabilities
Weakness
CWE-22
Published
2026-08-24
NVD CVE.org

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