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.

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Advisories
Source ID Title
Github GHSA Github GHSA GHSA-259r-337f-4rfw Compress/s2: Integer Overflow or Wraparound and Out-of-bounds Write in compress
Fixes

Solution

No solution given by the vendor.


Workaround

No workaround given by the vendor.

History

Fri, 02 Oct 2026 00:15:00 +0000

Type Values Removed Values Added
Weaknesses CWE-823
References
Metrics threat_severity

None

threat_severity

Important


Wed, 30 Sep 2026 21:00:00 +0000

Type Values Removed Values Added
First Time appeared Klauspost
Klauspost compress
Vendors & Products Klauspost
Klauspost compress

Tue, 29 Sep 2026 17:30:00 +0000

Type Values Removed Values Added
Metrics ssvc

{'options': {'Automatable': 'yes', 'Exploitation': 'none', 'Technical Impact': 'partial'}, 'version': '2.0.3'}


Tue, 29 Sep 2026 15:15:00 +0000

Type Values Removed Values Added
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.
Title Integer Overflow or Wraparound and Out-of-bounds Write in compress
Weaknesses CWE-190
CWE-787
References
Metrics cvssV3_1

{'score': 7.5, 'vector': 'CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H'}


Projects

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cve-icon MITRE

Status: PUBLISHED

Assigner: GitHub_M

Published:

Updated: 2026-09-29T16:32:32.677Z

Reserved: 2026-07-15T22:19:06.906Z

Link: CVE-2026-63209

cve-icon Vulnrichment

Updated: 2026-09-29T16:31:49.434Z

cve-icon NVD

Status : Deferred

Published: 2026-09-29T15:17:27.130

Modified: 2026-09-30T19:57:08.043

Link: CVE-2026-63209

cve-icon Redhat

Severity : Important

Publid Date: 2026-09-29T14:58:53Z

Links: CVE-2026-63209 - Bugzilla

cve-icon OpenCVE Enrichment

Updated: 2026-10-02T02:00:14Z

Weaknesses