CVE-2025-68131
CBORDecoder reuse can leak shareable values across decode calls
Reported by github_m · Published December 31, 2025
cbor2 is fixed in 5.8.0 (PyPI)
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.
Fixed versions
Upgrade to a fixed version or later. Language registries are listed first, then Linux distributions, then vendor products.
| Package | Ecosystem | Fixed in |
|---|---|---|
| cbor2 | PyPI | 5.8.0 |
Risk scores
Affected products
| Vendor | Product | Versions |
|---|---|---|
| agronholm | cbor2 | >= 3.0.0, < 5.8.0 |
| agronholm | cbor2 | 3.0.0 |
| PyPI | cbor2 | 3.0.0 |
| chainguard | py3-vllm-cuda-12.4 | 0 |
| chainguard | tritonserver-backend-vllm-cuda-12.9 | 0 |
| chainguard | authentik-fips | 0 |
| chainguard | localstack | 0 |
| chainguard | authentik | 0 |
Timeline
- Dec 30, 2025 PoC Published (7 in total, the first dated here)
- Dec 31, 2025 CVE Published
- Dec 31, 2025 EPSS Score (30 in total, the first dated here)
- Jan 2, 2026 CVE Updated
- Mar 9, 2026 Security Advisory
- Mar 26, 2026 Coalition ESS Score (2 in total, the first dated here)
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References
- https://github.com/agronholm/cbor2/security/advisories/GHSA-wcj4-jw5j-44wh x_refsource_CONFIRM
- https://github.com/agronholm/cbor2/pull/268 x_refsource_MISC
- https://nvd.nist.gov/vuln/detail/CVE-2025-68131 advisory
- https://github.com/advisories/GHSA-wcj4-jw5j-44wh advisory
- https://github.com/agronholm/cbor2/commit/f1d701cd2c411ee40bb1fe383afe7f365f35abf0 patch
- https://github.com/pypa/advisory-database/tree/main/vulns/cbor2/PYSEC-2025-90.yaml advisory