Potential buffer overflow in CBOR2 decoder

Exploitation

No confirmed exploitation recorded. Patch Next marks exploitation only from CISA KEV.

CVSS

7.5 · CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

EPSS

• CVE-2024-26134: 1.18% estimated exploitation activity in the next 30 days; percentile 67.63 (FIRST EPSS, 2026-11-03). This is a model estimate, not proof of exploitation or customer exposure.

As published by the source; long descriptions are shortened.

Summary Ever since https://github.com/agronholm/cbor2/pull/204 (or specifically https://github.com/agronholm/cbor2/commit/387755eacf0be35591a478d3c67fe10618a6d542) was merged, I can create a reproducible crash when running the snippet under PoC on a current Debian bullseye aarm64 on a Raspberry Pi 3 (I was not able to reproduce this on my x8664 Laptop with Python 3.11; I suspect because there is enough memory to allocate still) Details PoC If one calls it without the indirection via the pool executor, a SystemError is shown that hides the buffer overflow. Impact An attacker can crash a service using cbor2 to parse a CBOR binary by sending a long enough object.

Published by the source

21 Feb 2024, 00:09 UTC

Last modified by the source

10 Jun 2026, 17:14 UTC

Source last checked

26 Oct 2026, 13:37 UTC

1. Revision 2 · amended · 26 Oct 2026

   Amended from ghsa record GHSA-375g-39jq-vq7m

2. Revision 1 · created · 24 Oct 2026

   Published from osv record GHSA-375g-39jq-vq7m

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# Patch Next advisory brief: CVE-2024-26134

Advisory: Potential buffer overflow in CBOR2 decoder
IDs: CVE-2024-26134, GHSA-375g-39jq-vq7m
Record: https://patchnext.com/advisories/cve-2024-26134 (revision 2, source checked 26 Oct 2026, 13:37 UTC)
Inventory: none attached. This brief comes from a public page and does not say whether any deployment is affected.
Severity: High (CVSS 7.5)
Exploitation: no confirmed exploitation recorded. Patch Next confirms exploitation only from CISA KEV.
Vendor response: Vendor fix available; fixed versions by package: cbor2 5.6.2. A vendor fix does not mean a deployment is fixed.

## Affected components
- PyPI cbor2: affected >= 5.5.1, < 5.6.2; fixed in 5.6.2

## Suggested inspection (read-only)
- `python -m pip show cbor2`: prints the installed version. Run with the environment that serves production active.

## Supported action
Upgrade each affected component to a fixed version on its release line. For a transitive dependency, upgrade the parent package or add an override or constraint, then regenerate the lockfile. Redeploy every environment that ran an affected version.

## Required regression checks
- Run the test suite and a production build.
- Exercise the features that depend on cbor2.
- Repeat the inspection and confirm that only fixed versions remain installed.

## Rollback considerations
- Keep the previous lockfile and deployment artifact. Rolling back reinstates the vulnerable version, so apply any documented mitigation while you fix forward.

## Unresolved questions
- Which deployments run an affected version?
- Exploitation status can change. Check again before lowering the priority.
- Mark the work resolved only after the fixed version is verified in production.

## Sources
- Verified: https://osv.dev/vulnerability/GHSA-375g-39jq-vq7m (OSV record GHSA-375g-39jq-vq7m lists affected ranges: PyPI cbor2 >=5.5.1 <5.6.2 (fixed))
- Verified: https://github.com/advisories/GHSA-375g-39jq-vq7m (GitHub-reviewed advisory GHSA-375g-39jq-vq7m lists affected ranges: PyPI cbor2 >=5.5.1 <5.6.2)

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