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Advisory record · GHSA-wcj4-jw5j-44wh

CBORDecoder reuse can leak shareable values across decode calls

CVSS 5.5 MediumEPSS 0.0046 · 39th percentile

Published by the GitHub Advisory Database at 31 Dec 2025, 22:01 UTC. agentprime has not analysed this yet, so whether it affects any app is not known.

PackageEcosystemAffectedFixed in
cbor2PyPI>=3.0.0, <5.8.05.8.0
Identifiers
GHSA-wcj4-jw5j-44wh · CVE-2025-68131 · PYSEC-2025-90
Weakness (CWE)
CWE-212
Tags
Published
31 Dec 2025
Updated
10 Sept 2026

Machine-written summary

Summary written by Claude Haiku from the source advisory. Not reviewed by a person.

The cbor2 package, versions 3.0.0 before 5.8.0, has a flaw where a reused CBORDecoder instance keeps shareable values (tag 28) between decode calls, so a later message using sharedref (tag 29) can read values from earlier messages. An attacker who can supply CBOR messages to a reused decoder can read previously decoded data, which may expose sensitive information. Upgrade cbor2 to 5.8.0 or later. Avoid reusing a single CBORDecoder across different trust boundaries.

Written 5 Nov 2026.

Not analysed yet

We haven’t published our analysis of this Advisory yet. Once a person has reviewed it, this page will say what’s vulnerable, what has to be true for your app to be affected, and how to check.

Severity and exploitation

ScoreRatingCVSSVectorSource
5.5 Medium 4.0 CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:L/VI:N/VA:L/SC:N/SI:N/SA:N/E:P CNA (GitHub_M)
  • CISA KEV Not listed.
  • EPSS 0.0046, the 39th percentile, on 5 Nov 2026: FIRST’s estimate of the chance of exploitation in the next 30 days.

Timeline

  1. 31 Oct 2026, 14:36 UTC First seen by agentprime
  2. 31 Oct 2026, 14:36 UTC Confirmed by OSV

Sources

Facts on this page come from the GitHub Advisory Database (CC-BY 4.0), OSV and the other sources listed, as published. We don’t reproduce full advisory descriptions, which can contain exploit code.