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CVE-2026-63209

7.5 · HIGH

compress provides various compression algorithms.

Published Sep 29, 2026CWE-190EPSS 0.57%

Overview

CVE-2026-63209 is a high-severity vulnerability. It was published on September 29, 2026 and has a CVSS 3.1 base score of 7.5 (HIGH).

This vulnerability has a CVSS 3.1 base score of 7.5, rated HIGH. It can be exploited remotely over the network. No authentication or special privileges are required for exploitation.

Technical 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.

Remediation

Check the references section for vendor advisories, patches, and mitigation guidance. If immediate patching is not possible, review the CVSS vector to understand the attack surface and apply compensating controls such as network segmentation or access restrictions.

References

GitHubgithub.com/klauspost/compress/commit/539243b8823ee8f03e49969823d57c348c917536GitHubgithub.com/klauspost/compress/releases/tag/v1.18.7GitHubgithub.com/klauspost/compress/security/advisories/GHSA-259r-337f-4rfwGitHubgithub.com/klauspost/compress/security/advisories/GHSA-259r-337f-4rfw

How CyberStrike helps

Frequently asked questions

What is CVE-2026-63209?

CVE-2026-63209 is a high-severity vulnerability. It was published on September 29, 2026 and has a CVSS 3.1 base score of 7.5 (HIGH).

How severe is CVE-2026-63209?

This vulnerability has a CVSS 3.1 base score of 7.5, rated HIGH. It can be exploited remotely over the network. No authentication or special privileges are required for exploitation.

How do I fix or remediate CVE-2026-63209?

Check the references section for vendor advisories, patches, and mitigation guidance. If immediate patching is not possible, review the CVSS vector to understand the attack surface and apply compensating controls such as network segmentation or access restrictions.

How can CyberStrike help with CVE-2026-63209?

CyberStrike is an open-source, AI-augmented pentesting engine. Rather than flag a version number, it tests whether an issue like CVE-2026-63209 is actually reachable in your own applications and APIs, then verifies each finding before reporting it. That tells you if the weakness is a real, exploitable risk in your environment or a false positive you can safely deprioritize.

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