VulnerabilityPublished 2 Jul 2026

CVE-2026-52736: Zebra state · Zebra has block suppression via NU5 same-header body poisoning of sent-hash cache

Affects zebra-stateSource GCVE Database

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Authoritative record:CVE-2026-52736· High 8.7

Not known to be exploited · CVSS 8.7 High : upgrade to 7.0.0 soon.

Data as of 30 Oct 2026, 06:59 UTC

CVSS 4.0 base score

8.7High

How severe the flaw is on the 0–10 CVSS scale.

EPSS: 0.6% chance of exploitation in 30 days – higher than 49% of CVEsExploit Prediction Scoring System: the likelihood attackers will use this flaw soon.
Patch: Available – fixed in 7.0.0, 4.5.0

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

Attack Vector: Network
Attack Complexity: Low
Attack Requirements: None
Privileges Required: None
User Interaction: None
Vulnerable system confidentiality: None
Vulnerable system integrity: High
Vulnerable system availability: None
Subsequent system confidentiality: None
Subsequent system integrity: None
Subsequent system availability: None

Bold values are the worst case: easiest to exploit or largest impact.

Attack Vector: Network: The vulnerable system is bound to the network stack and the set of possible attackers extends beyond the other options listed below, up to and including the entire Internet. Such a vulnerability is often termed “remotely exploitable” and can be thought of as an attack being exploitable at the protocol level one or more network hops away (e.g., across one or more routers).
Attack Complexity: Low: The attacker must take no measurable action to exploit the vulnerability. The attack requires no target-specific circumvention to exploit the vulnerability. An attacker can expect repeatable success against the vulnerable system.
Attack Requirements: None: The successful attack does not depend on the deployment and execution conditions of the vulnerable system. The attacker can expect to be able to reach the vulnerability and execute the exploit under all or most instances of the vulnerability.
Privileges Required: None: The attacker is unauthorized prior to attack, and therefore does not require any access to settings or files of the vulnerable system to carry out an attack.
User Interaction: None: The vulnerable system can be exploited without interaction from any human user, other than the attacker.
Vulnerable system confidentiality: None: There is no loss of confidentiality within the Vulnerable System.
Vulnerable system integrity: High: There is a total loss of integrity, or a complete loss of protection. For example, the attacker is able to modify any/all files protected by the vulnerable system. Alternatively, only some files can be modified, but malicious modification would present a direct, serious consequence to the vulnerable system.
Vulnerable system availability: None: There is no impact to availability within the Vulnerable System.
Subsequent system confidentiality: None: There is no loss of confidentiality within the Subsequent System or all confidentiality impact is constrained to the Vulnerable System.
Subsequent system integrity: None: There is no loss of integrity within the Subsequent System or all integrity impact is constrained to the Vulnerable System.
Subsequent system availability: None: There is no impact to availability within the Subsequent System or all availability impact is constrained to the Vulnerable System.

Definitions: FIRST CVSS v4.0 specification.

Exploitation evidence

Disclosed: evidence found.
CVE published 18 Aug 2026
Detectable: no evidence on record.
No public nuclei template indexed
Weaponized: no evidence on record.
No public exploit code indexed in Metasploit or Exploit-DB
Exploited in the wildExploited: no evidence on record.
Not in CISA KEV and no source reports exploitation
Observed by OffSeq MirageSeen by Mirage: no evidence on record.
No attack traffic recorded by OffSeq Mirage sensors

A missing step is not evidence of safety. Sources: cve.org (opens in a new tab), the Metasploit, Exploit-DB and nuclei-templates index as of 29 Oct 2026.

Disclosed: The CVE record is public on cve.org. Its publication is t = 0.
Detectable: A public nuclei template can find exposed instances, for defenders and attackers alike.
Weaponized: A Metasploit exploit module or Exploit-DB entry exists (Metasploit scanner modules do not count), or CISA SSVC or the CVSS exploit maturity reports a public proof of concept.
Exploited in the wild: CISA KEV lists it, CISA SSVC rates exploitation active, or a source reports attacks.
Observed by OffSeq Mirage: OffSeq Mirage honeypot sensors recorded attack traffic for this CVE, or found exposed hosts without attack traffic.

Moments are spaced evenly, not to scale; a dashed line marks a gap of six months or more. Deltas count from t = 0. Sources that give only a date (CISA KEV, Exploit-DB, or a time of exactly 00:00Z) read “same day” rather than hours. Metasploit modules carry the flaw’s disclosure date, not their release date, and nuclei templates carry no date, so both appear above but not on the timeline.

What to do

Upgrade zebra-state to 7.0.0; zebrad to 4.5.0.

Affected software

Product	Affected	Fixed in
crates.iozebra-state	Affected <7.0.0	Fixed in 7.0.0
crates.iozebrad	Affected <4.5.0	Fixed in 4.5.0

Check your own hosts for these packages with threat-finder (opens in a new tab), our free open-source scanner.

AI-suggested

An official patch is available in Zebra version 4.4.2 that fixes this issue by removing stale entries from the sent-hash cache on failed validation. Users should upgrade to Zebra 4.4.2 or later. There is no complete configuration workaround; reducing inbound peer count can reduce but not eliminate risk. Restarting the node clears the in-memory cache and allows recovery if the node is stalled. Operators should apply the patch promptly to prevent potential denial of service via block suppression.

Description

ZEBRA is a Zcash node written entirely in Rust. Prior to 4.5.0, a remote unauthenticated P2P peer can stall a Zebra node by racing an invalid block body against the valid canonical body for the same block header hash. ZIP-244 permits the attacker to mutate coinbase scriptSig authentication data while retaining the transaction identifiers, merkle root, and block header hash, so the poisoned body fails later commitment validation but shares the canonical hash. In zebra-state/src/service.rs, queue_and_commit_to_non_finalized_state recorded the hash in non_finalized_block_write_sent_hashes before contextual validation completed and did not remove it when the write task rejected the body. When the honest body later arrived, the cached hash caused KnownBlock::WriteChannel duplicate handling to suppress it, leaving the node stuck one height behind until restart or reorganization. This issue is fixed in version 4.5.0.

Impact

A remote unauthenticated peer can cause a Zebra node to permanently stall at a specific block height by delivering a poisoned block body that causes the node to cache a block hash erroneously. This prevents the node from accepting the valid canonical block, causing it to diverge from the network tip. Downstream services relying on the node will see a stalled chain. The attack requires winning a propagation race and can be sustained to keep the node behind the network indefinitely. Recovery requires node restart or a rare chain reorganization. This impacts network reliability and data freshness for affected nodes.

Summary

Zebra's zebrad client up to and including v4.4.1 is vulnerable to a block suppression attack via a poisoned block body sharing a header hash with a valid canonical block. The node caches the block hash in non_finalized_block_write_sent_hashes before validation. If validation fails due to a poisoned block body (crafted by mutating the coinbase scriptSig extra-data under ZIP-244 malleability), the hash remains cached. When the valid block arrives, it is rejected as a duplicate, causing the node to stall at that height. This can be exploited by a remote unauthenticated P2P peer who wins the propagation race. The vulnerability also affects chain pruning scenarios leaving stale hashes in the cache. The issue is fixed in Zebra 4.4.2 by removing stale hashes on failed writes. There is no full configuration workaround; node restart clears the cache and allows recovery.

CWE-459Incomplete Cleanup (opens in a new tab)
Base weakness
The product does not properly "clean up" and remove temporary or supporting resources after they have been used.
Architecture and Design · Implementation
Temporary files and other supporting resources should be deleted/released immediately after they are no longer needed.
From MITRE CWE, MITRE CAPEC and OWASP (Top 10, OpenCRE).

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Exploitation evidence

What to do

Affected software

Description

AI analysisMachine-generated, updated 19 Aug 2026, 11:13 UTC

WeaknessesCWE-459

Technical details

References

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