High
Integer Overflow or Wraparound and Out-of-bounds Write in compress
Type: advisorySources: OSV
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.
- Products
- Not specified
- Affected versions
- Not specified
- Fixed versions
- Not specified
- CVEs
- CVE-2026-63209
- Confirmed fixed CVEs
- Not specified
- Updated in this feed
- 3 Nov 2026, 23:09 UTC · Revision 1
Source evidence
Integer Overflow or Wraparound and Out-of-bounds Write in compress
core-osv · Original sourcePublished 29 Sept 2026, 14:58 UTC
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.
osv:CVE-2026-63209
Complete source record
{
"id": "5f53bd78e8661a1ada65cfb7be8678371ce32cb3551b4bed3232ff93d9850975",
"url": "https://osv.dev/vulnerability/CVE-2026-63209",
"method": "structured",
"payload": {
"kind": "advisory",
"title": "Integer Overflow or Wraparound and Out-of-bounds Write in compress",
"summary": "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.",
"evidence": "osv:CVE-2026-63209",
"products": [],
"severity": "high",
"structured": {
"id": "CVE-2026-63209",
"aliases": [
"CVE-2026-63209",
"GHSA-259r-337f-4rfw",
"GO-2026-5841"
],
"metrics": [
{
"type": "CVSS_V3",
"score": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H"
}
],
"affected": [
{
"ranges": [
{
"repo": "https://github.com/klauspost/compress",
"type": "GIT",
"events": [
{
"introduced": "0"
},
{
"fixed": "8668e357e776d5152ed62f33c17f21b8690664fa"
},
{
"fixed": "539243b8823ee8f03e49969823d57c348c917536"
}
],
"database_specific": {
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"range": [
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{
"fixed": "1.18.7"
}
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"source": "AFFECTED_FIELD",
"strategy": "StringRangeExpression"
},
{
"range": [
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],
"source": "REFERENCES_COMMIT"
},
{
"range": [
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"source": "REFERENCES_TAG",
"original_tag": "v1.18.7"
}
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],
"database_specific": {
"source": "https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2026-63209.json"
}
}
],
"modified": "2026-10-28T02:30:32.127502738Z",
"provider": "osv",
"references": [
"https://github.com/klauspost/compress/releases/tag/v1.18.7",
"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/63xxx/CVE-2026-63209.json",
"https://github.com/klauspost/compress/security/advisories/GHSA-259r-337f-4rfw",
"https://nvd.nist.gov/vuln/detail/CVE-2026-63209",
"https://github.com/klauspost/compress/commit/539243b8823ee8f03e49969823d57c348c917536"
],
"provider_metadata": {
"cwe_ids": [
"CWE-190",
"CWE-787"
],
"cna_assigner": "GitHub_M",
"osv_generated_from": "https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/63xxx/CVE-2026-63209.json"
}
},
"related_cves": [
{
"value": "CVE-2026-63209",
"evidence": "/id"
}
],
"security_relevant": true,
"severity_evidence": "/severity/0/score"
},
"source_id": "core-osv",
"document_id": 499225,
"published_at": "2026-09-29T14:58:53.366+00:00"
}