CVE-2026-63209
High
Description
compress provides various compression algorithms. Prior to version 1.18.7, a signed integer overflow vulnerability in s2.NewDict() allows an attacker to bypass repeat index validation by supplying a dictionary with a uvarint-encoded repeat value exceeding MaxInt64. When Dict.Encode() is subsequently called, the overflowed negative repeat value causes an out-of-bounds memory access via unsafe.Pointer arithmetic, crashing the process with SIGSEGV. This issue has been patched in version 1.18.7.
SeverityHigh
CVSS7.5
Exploit probability—
ProductGithub.com/klauspost/compress
PublishedSep 29, 2026
First seenSep 29, 2026
Weakness typeCWE-190Integer overflowCWE-787Out-of-bounds write
How to fix
Update
- github.com/klauspost/compress1.18.7 or later
Affected products
| Product | Affected versions | Fixed in |
|---|---|---|
| github.com/klauspost/compressGo | v < 1.18.7, 1.16.0 ≤ v < 1.18.7 | 1.18.7 |
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