Vulnerability · Published Sep 29, 2026 · Assigned by GitHub_M
CVE-2026-63209Integer Overflow or Wraparound and Out-of-bounds Write in compress
High 7.5
In plain English
A high-severity integer overflow in compress from klauspost. There are no confirmed reports of exploitation so far. The chance it is exploited in the next 30 days is estimated at 0.6% (higher than 47% of all known vulnerabilities). Fixed versions are available - upgrade the affected package.
Official 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.
Affected packages & fixed versions
| Ecosystem | Package | Fixed in | Advisory |
|---|---|---|---|
| Debian:13 | golang-github-klauspost-compress | no fix listed | DEBIAN-CVE-2026-63209 |
| Debian:14 | golang-github-klauspost-compress | 1.19.0+ds1-1 | DEBIAN-CVE-2026-63209 |
| Go | github.com/klauspost/compress | 1.18.7 | GHSA-259r-337f-4rfw |
| Go | github.com/klauspost/compress | 1.18.7 | GO-2026-5841 |
| Ubuntu:22.04:LTS | golang-github-klauspost-compress | no fix listed | UBUNTU-CVE-2026-63209 |
| Ubuntu:24.04:LTS | golang-github-klauspost-compress | no fix listed | UBUNTU-CVE-2026-63209 |
| Ubuntu:26.04:LTS | golang-github-klauspost-compress | no fix listed | UBUNTU-CVE-2026-63209 |
| Ubuntu:26.10 | golang-github-klauspost-compress | no fix listed | UBUNTU-CVE-2026-63209 |
Affected products (as reported)
Weakness: CWE-190, CWE-787 · Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H