PYSEC-2020-29

Exploitation

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

CVSS 4.0

6.9 · CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:L/VA:L/SC:N/SI:N/SA:N · score source

EPSS

• CVE-2020-36846: 0.66% estimated exploitation activity in the next 30 days; percentile 51.65 (FIRST EPSS, 2026-11-03). This is a model estimate, not proof of exploitation or customer exposure.
• CVE-2020-8927: 3.22% estimated exploitation activity in the next 30 days; percentile 88.22 (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.

A buffer overflow exists in the Brotli library versions prior to 1.0.8 where an attacker controlling the input length of a "one-shot" decompression request to a script can trigger a crash, which happens when copying over chunks of data larger than 2 GiB. It is recommended to update your Brotli library to 1.0.8 or later. If one cannot update, we recommend to use the "streaming" API as opposed to the "one-shot" API, and impose chunk size limits.

Published by the source

15 Sep 2020, 10:15 UTC

Last modified by the source

10 Jun 2026, 17:00 UTC

Source last checked

25 Oct 2026, 01:37 UTC

1. Revision 2 · amended · 25 Oct 2026

   Reviewed OSV alias/range/CVSS4 correction; package source scopes and original publication preserved. No customer finding resolved.

2. Revision 1 · created · 24 Oct 2026

   Published from osv record PYSEC-2020-29

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# Patch Next advisory brief: CVE-2020-36846

Advisory: PYSEC-2020-29
IDs: CVE-2020-36846, GHSA-5v8v-66v8-mwm7
Record: https://patchnext.com/advisories/cve-2020-36846 (revision 2, source checked 25 Oct 2026, 01:37 UTC)
Inventory: none attached. This brief comes from a public page and does not say whether any deployment is affected.
Severity: Medium (CVSS 6.9)
Exploitation: no confirmed exploitation recorded. Patch Next confirms exploitation only from CISA KEV.
Vendor response: Vendor fix available; fixed versions by package: brotli 1.0.8. A vendor fix does not mean a deployment is fixed.

## Affected components
- PyPI brotli: affected < 1.0.8; fixed in 1.0.8

## Suggested inspection (read-only)
- `python -m pip show brotli`: 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 brotli.
- 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/PYSEC-2020-29 (OSV record PYSEC-2020-29 lists affected ranges: PyPI brotli >=0 <1.0.8 (fixed))

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