Zebra has Permanent Block Discovery Halt via Gossip Queue Saturation and Syncer Poisoning

Exploitation

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

CVSS 4.0

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

EPSS

• CVE-2026-44499: 0.35% estimated exploitation activity in the next 30 days; percentile 28.84 (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 A composite denial-of-service vulnerability in Zebra's block discovery pipeline allows an unauthenticated remote attacker to permanently halt all new block discovery on a targeted node. The attack exploits three independent weaknesses in the gossip, syncer, and download subsystems — all exercisable from a single TCP connection — to create a monotonically growing block deficit that never self-heals. Severity Critical — This is a Denial of Service vulnerability that requires no authentication, no special privileges, and only a single peer connection. The halt is permanent: the node will never recover without operator intervention. Affected Versions All Zebra versions prior to 4.4.0. Description Zebra discovers new blocks through two complementary paths: a gossip path (peers announce blocks via inv messages, triggering individual block downloads) and a syncer path (Zebra periodically queries peers with FindBlocks/FindHeaders to discover chains of missing blocks). Both paths must…

Published by the source

8 May 2026, 19:12 UTC

Last modified by the source

18 May 2026, 17:07 UTC

Source last checked

26 Oct 2026, 15:42 UTC

1. Revision 1 · created · 26 Oct 2026

   Published from ghsa record GHSA-h9hm-m2xj-4rq9

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# Patch Next advisory brief: CVE-2026-44499

Advisory: Zebra has Permanent Block Discovery Halt via Gossip Queue Saturation and Syncer Poisoning
IDs: CVE-2026-44499, GHSA-h9hm-m2xj-4rq9
Record: https://patchnext.com/advisories/cve-2026-44499 (revision 1, source checked 26 Oct 2026, 15:42 UTC)
Inventory: none attached. This brief comes from a public page and does not say whether any deployment is affected.
Severity: High (CVSS 8.7)
Exploitation: no confirmed exploitation recorded. Patch Next confirms exploitation only from CISA KEV.
Vendor response: Vendor fix available; fixed versions by package: zebrad 4.4.0. A vendor fix does not mean a deployment is fixed.

## Affected components
- crates.io zebrad: affected < 4.4.0; fixed in 4.4.0

## Suggested inspection (read-only)
- crates.io zebrad: check the installed version with your package manager.

## 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 zebrad.
- 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://github.com/advisories/GHSA-h9hm-m2xj-4rq9 (GitHub-reviewed advisory GHSA-h9hm-m2xj-4rq9 lists affected ranges: crates.io zebrad >=0 <4.4.0)

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