zae-limiter: DynamoDB hot partition throttling enables per-entity Denial of Service

Exploitation

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

CVSS

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

EPSS

• CVE-2026-27695: 0.27% estimated exploitation activity in the next 30 days; percentile 18.84 (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 All rate limit buckets for a single entity share the same DynamoDB partition key (namespace/ENTITY#{id}). A high-traffic entity can exceed DynamoDB's per-partition throughput limits (~1,000 WCU/sec), causing throttling that degrades service for that entity — and potentially co-located entities in the same partition. Details Each acquire() call performs a TransactWriteItems (or UpdateItem in speculative mode) against items sharing the same partition key. For cascade entities, this doubles to 2-4 writes per request (child + parent). At sustained rates above ~500 req/sec for a single entity, DynamoDB's adaptive capacity may not redistribute fast enough, causing ProvisionedThroughputExceededException. The library has no built-in mitigation: - No partition key sharding/salting - No write coalescing or batching - No client-side admission control before hitting DynamoDB - RateLimiterUnavailable is raised but the caller has already been delayed Impact - Availability: High-traffic…

Published by the source

25 Feb 2026, 22:31 UTC

Last modified by the source

13 Jul 2026, 16:42 UTC

Source last checked

26 Oct 2026, 13:36 UTC

1. Revision 2 · amended · 26 Oct 2026

   Amended from ghsa record GHSA-76rv-2r9v-c5m6

2. Revision 1 · created · 24 Oct 2026

   Published from osv record GHSA-76rv-2r9v-c5m6

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# Patch Next advisory brief: CVE-2026-27695

Advisory: zae-limiter: DynamoDB hot partition throttling enables per-entity Denial of Service
IDs: CVE-2026-27695, GHSA-76rv-2r9v-c5m6
Record: https://patchnext.com/advisories/cve-2026-27695 (revision 2, source checked 26 Oct 2026, 13:36 UTC)
Inventory: none attached. This brief comes from a public page and does not say whether any deployment is affected.
Severity: Medium (CVSS 4.3)
Exploitation: no confirmed exploitation recorded. Patch Next confirms exploitation only from CISA KEV.
Vendor response: Vendor fix available; fixed versions by package: zae-limiter 0.10.1. A vendor fix does not mean a deployment is fixed.

## Affected components
- PyPI zae-limiter: affected <= 0.10.0; fixed in 0.10.1

## Suggested inspection (read-only)
- `python -m pip show zae-limiter`: 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 zae-limiter.
- 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-76rv-2r9v-c5m6 (OSV record GHSA-76rv-2r9v-c5m6 lists affected ranges: PyPI zae-limiter >=0 <0.10.1 (fixed))
- Verified: https://github.com/advisories/GHSA-76rv-2r9v-c5m6 (GitHub-reviewed advisory GHSA-76rv-2r9v-c5m6 lists affected ranges: PyPI zae-limiter >=0 <=0.10.0)

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