What’s Vulnerable › Vulnerabilities

CVE-2025-68131: CBORDecoder reuse can leak shareable values across decode calls

• Severity: high (CVSS 7.5 v3.1)
• Exploited in the wild: not listed in CISA KEV
• EPSS: 0.5% probability of exploitation in the next 30 days
• Public exploit or detection template: yes
• Published: 2025-12-31 · updated 2026-06-17
• Weakness: CWE-212

Description

cbor2 provides encoding and decoding for the Concise Binary Object Representation (CBOR) serialization format. Starting in version 3.0.0 and prior to version 5.8.0, whhen a CBORDecoder instance is reused across multiple decode operations, values marked with the shareable tag (28) persist in memory and can be accessed by subsequent CBOR messages using the sharedref tag (29). This allows an attacker-controlled message to read data from previously decoded messages if the decoder is reused across trust boundaries. Version 5.8.0 patches the issue.

Affected products

• agronholm cbor2: from 3.0.0 before 5.8.0 — fixed in 5.8.0

How to fix

Upgrade to a fixed version: agronholm cbor2 5.8.0. Check the vendor advisory for mitigations.

References

• https://github.com/agronholm/cbor2/pull/268
• https://github.com/agronholm/cbor2/security/advisories/GHSA-wcj4-jw5j-44wh
• https://github.com/agronholm/cbor2/security/advisories/GHSA-wcj4-jw5j-44wh

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