CVE-2026-63209 Details
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.
A signed integer overflow vulnerability has been identified in the Klauspost Compress library, specifically in the S2 compression module, prior to version 1.18.7. The issue arises in the `s2.NewDict()` function, where an attacker can bypass repeat index validation by providing a dictionary with a uvarint-encoded repeat value that exceeds the maximum integer limit. This overflow leads to an out-of-bounds memory access, causing the process to crash with a segmentation fault. The vulnerability is present in all versions of the library that include the `NewDict` function, up to and including 1.18.6.
Users can upgrade to Klauspost Compress version 1.18.7 or later, where this vulnerability has been patched.
Metrics
CVSS 4.0 Severity and Vector Strings:
VolerionCVSS 3.x Severity and Vector Strings:
No data available for CVSS Version 2.0 on this CVE.
Volerion
Assessed Sep 29, 2026CISA-ADP
Assessed Sep 29, 2026References to Advisories, Solutions, and Tools
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| URL | Source(s) | Tag(s) |
|---|---|---|
| https://github.com/klauspost/compress/security/advisories/GHSA-259r-337f-4rfw | CISA-ADP | AdvisoryExploitRemedyVendor |
| https://github.com/klauspost/compress/commit/539243b8823ee8f03e49969823d57c348c917536 | [email protected] | Source CodeVendor |
| https://github.com/klauspost/compress/releases/tag/v1.18.7 | [email protected] | Release NotesVendor |
| https://github.com/klauspost/compress/security/advisories/GHSA-259r-337f-4rfw | [email protected] | AdvisoryExploitRemedyVendor |
Weakness Enumeration
| CWE-ID | CWE Name | Source |
|---|---|---|
| CWE-190 | Integer Overflow or Wraparound | [email protected] |
| CWE-787 | Out-of-bounds Write | [email protected] |
Affected Products
| Product | Versions |
|---|---|
| klauspost compress | <= 1.18.6 (semver) |
CPE
Remediation
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Change History
2 change records found show changes
| Date | Action | Recorded By |
|---|---|---|
| Sep 29, 2026 | CVE Modified | CISA-ADP |
| Sep 29, 2026 | New CVE Received | [email protected] |