CVE-2026-63209: Integer Overflow or Wraparound and Out-of-bounds Write in compress
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 Software
Remediation
Recommended actions to resolve this vulnerability, in priority order.
- Upgrade
Upgrade to a fixed release to a version that resolves this vulnerability.
Fixed in 1.18.7
Event History
Frequently Asked Questions
What conditions are required to trigger the crash?
An attacker must be able to supply a crafted dictionary containing a uvarint-encoded repeat value greater than MaxInt64, and the application must subsequently call Dict.Encode() on that dictionary. The overflowed value can then lead to an out-of-bounds access and SIGSEGV.
What is the impact of successful exploitation?
Successful exploitation crashes the affected process with SIGSEGV, resulting in a denial of service. The provided information describes no confidentiality or integrity impact.
Which versions need to be updated?
Versions prior to 1.18.7 are affected. The issue is patched in version 1.18.7.