Vulnerability-Lookup

CVE-2026-44498 (GCVE-0-2026-44498)

Vulnerability from cvelistv5 – Published: 2026-05-08 15:09 – Updated: 2026-05-14 21:32

Title

ZEBRA: Block Validator Undercounts Coinbase and P2SH Sigops

Summary

ZEBRA is a Zcash node written entirely in Rust. Prior to version 4.4.0, Zebra's block validator undercounts transparent signature operations against the 20000-sigop block limit (MAX_BLOCK_SIGOPS), allowing it to accept blocks that zcashd rejects with bad-blk-sigops. A miner who produces such a block can split the network: Zebra nodes follow the offending chain while zcashd nodes do not. This issue has been patched in version 4.4.0.

Severity

9.2 (Critical)


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

SSVC

Exploitation: none Automatable: yes Technical Impact: total

CISA Coordinator · CISA-ADP (v2.0.3)

Decision recorded 2026-05-13 16:11 UTC

CWE

CWE-682 - Incorrect Calculation

Assigner

GitHub_M mitre root

References

2 references

URL	Tags
https://github.com/ZcashFoundation/zebra/security…	x_refsource_CONFIRM
https://github.com/ZcashFoundation/zebra/releases…	x_refsource_MISC

Impacted products

1 product

Vendor	Product	Version	CPE status
ZcashFoundation	zebra	Affected: < 4.4.0	guessed

Show details on NVD website

JSON

To clipboard

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        }
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      ],
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      },
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    }
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          }
        ],
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      "source": "Red Hat CSAF VEX",
      "status": "final",
      "title": "ZEBRA: Block Validator Undercounts Coinbase and P2SH Sigops",
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    },
    "vulnrichment": {
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}

FKIE_CVE-2026-44498

Vulnerability from fkie_nvd - Published: 2026-05-08 15:17 - Updated: 2026-06-17 10:50

Severity

7.5 (High) - CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N

Summary

References

	URL	Tags
	security-advisories@github.com	https://github.com/ZcashFoundation/zebra/releases/tag/v4.4.0	Release Notes
	security-advisories@github.com	https://github.com/ZcashFoundation/zebra/security/advisories/GHSA-jv4h-j224-23cc	Vendor Advisory

Impacted products

	Vendor	Product	Version
	zfnd	zebrad	*

JSON

To clipboard

{
  "affected": [
    {
      "affectedData": [
        {
          "product": "zebra",
          "vendor": "ZcashFoundation",
          "versions": [
            {
              "status": "affected",
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            }
          ]
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    }
  ],
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    }
  ],
  "id": "CVE-2026-44498",
  "lastModified": "2026-06-17T10:50:43.737",
  "metrics": {
    "cvssMetricV31": [
      {
        "cvssData": {
          "attackComplexity": "LOW",
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          "availabilityImpact": "NONE",
          "baseScore": 7.5,
          "baseSeverity": "HIGH",
          "confidentialityImpact": "NONE",
          "integrityImpact": "HIGH",
          "privilegesRequired": "NONE",
          "scope": "UNCHANGED",
          "userInteraction": "NONE",
          "vectorString": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N",
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          "modifiedPrivilegesRequired": "NOT_DEFINED",
          "modifiedSubAvailabilityImpact": "NOT_DEFINED",
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    "ssvcV203": [
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}

GHSA-JV4H-J224-23CC

Vulnerability from github – Published: 2026-05-07 20:54 – Updated: 2026-05-13 13:28

Summary

Zebra's Block Validator Undercounts Coinbase and P2SH Sigops

Details

Zebra's block validator undercounts transparent signature operations against the 20000-sigop block limit (MAX_BLOCK_SIGOPS), allowing it to accept blocks that zcashd rejects with bad-blk-sigops. A miner who produces such a block can split the network: Zebra nodes follow the offending chain while zcashd nodes do not.

Two distinct undercounts:

A: Coinbase Hidden Legacy Sigops

zcashd's GetLegacySigOpCount() includes the coinbase input's scriptSig. Zebra's Sigops impl skipped the coinbase input entirely, so up to ~98 sigops (the 100-byte coinbase script length cap, less the height prefix) could be hidden inside the coinbase scriptSig without being charged against the block limit.

B: Aggregate P2SH Sigops.

zcashd's GetP2SHSigOpCount() parses each P2SH input's redeem script with accurate=true and sums those sigops into the block-wide total via ConnectBlock. The check is per-block, not per-transaction, and the limit applies regardless of who mines the offending block — a miner just needs to include enough P2SH-spending transactions whose redeem scripts together exceed 20000 sigops. Zebra computed P2SH sigops only on the mempool-acceptance path (used for ZIP-317 weighting) and never accumulated them during block validation. A block whose aggregate redeem-script sigops exceed 20000 (e.g. 1334 P2SH spends × 15 sigops = 20010) would be accepted by Zebra and rejected by zcashd.

Patches

Fixed in this release: https://github.com/ZcashFoundation/zebra/releases/tag/v4.4.0.

Workarounds

None. Operators relying on Zebra for consensus should upgrade.

Resources

MAX_BLOCK_SIGOPS constant inherited from Bitcoin via the Zcash protocol spec's §7.6 catch-all "Other rules inherited from Bitcoin", tracked for explicit documentation in zcash/zips#568.
zcashd GetLegacySigOpCount: https://github.com/zcash/zcash/blob/v6.11.0/src/main.cpp#L826-L836
zcashd GetP2SHSigOpCount: https://github.com/zcash/zcash/blob/v6.11.0/src/main.cpp#L840-L852
zcashd ConnectBlock aggregates per-tx sigops and compares against MAX_BLOCK_SIGOPS.

Severity

7.5 (High)


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

9.2 (Critical)


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

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{
  "affected": [
    {
      "package": {
        "ecosystem": "crates.io",
        "name": "zebrad"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "0"
            },
            {
              "fixed": "4.4.0"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ]
    }
  ],
  "aliases": [
    "CVE-2026-44498"
  ],
  "database_specific": {
    "cwe_ids": [
      "CWE-682"
    ],
    "github_reviewed": true,
    "github_reviewed_at": "2026-05-07T20:54:33Z",
    "nvd_published_at": "2026-05-08T15:17:01Z",
    "severity": "CRITICAL"
  },
  "details": "Zebra\u0027s block validator undercounts transparent signature operations against the 20000-sigop block limit (`MAX_BLOCK_SIGOPS`), allowing it to accept blocks that `zcashd` rejects with `bad-blk-sigops`. A miner who produces such a block can split the network: Zebra nodes follow the offending chain while `zcashd` nodes do not.\n\nTwo distinct undercounts:\n\n#### A: Coinbase Hidden Legacy Sigops\n\n`zcashd`\u0027s `GetLegacySigOpCount()` includes the coinbase input\u0027s `scriptSig`. Zebra\u0027s `Sigops` impl skipped the coinbase input entirely, so up to ~98 sigops (the 100-byte coinbase script length cap, less the height prefix) could be hidden inside the coinbase `scriptSig` without being charged against the block limit.\n\n#### B: Aggregate P2SH Sigops.\n\n`zcashd`\u0027s `GetP2SHSigOpCount()` parses each P2SH input\u0027s redeem script with `accurate=true` and sums those sigops into the block-wide total via `ConnectBlock`. The check is per-block, not per-transaction, and the limit applies regardless of who mines the offending block \u2014 a miner just needs to include enough P2SH-spending transactions whose redeem scripts together exceed 20000 sigops. Zebra computed P2SH sigops only on the mempool-acceptance path (used for ZIP-317 weighting) and never accumulated them during block validation. A block whose aggregate redeem-script sigops exceed 20000 (e.g. 1334 P2SH spends \u00d7 15 sigops = 20010) would be accepted by Zebra and rejected by `zcashd`.\n\n### Patches\n\nFixed in this release:  https://github.com/ZcashFoundation/zebra/releases/tag/v4.4.0.\n\n### Workarounds\n\nNone. Operators relying on Zebra for consensus should upgrade.\n\n### Resources\n\n- `MAX_BLOCK_SIGOPS` constant inherited from Bitcoin via the Zcash protocol spec\u0027s \u00a77.6 catch-all \"Other rules inherited from Bitcoin\", tracked for explicit documentation in [zcash/zips#568](https://github.com/zcash/zips/issues/568).\n- `zcashd` `GetLegacySigOpCount`: \u003chttps://github.com/zcash/zcash/blob/v6.11.0/src/main.cpp#L826-L836\u003e\n- `zcashd` `GetP2SHSigOpCount`: \u003chttps://github.com/zcash/zcash/blob/v6.11.0/src/main.cpp#L840-L852\u003e\n- `zcashd` `ConnectBlock` aggregates per-tx sigops and compares against `MAX_BLOCK_SIGOPS`.",
  "id": "GHSA-jv4h-j224-23cc",
  "modified": "2026-05-13T13:28:47Z",
  "published": "2026-05-07T20:54:33Z",
  "references": [
    {
      "type": "WEB",
      "url": "https://github.com/ZcashFoundation/zebra/security/advisories/GHSA-jv4h-j224-23cc"
    },
    {
      "type": "ADVISORY",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-44498"
    },
    {
      "type": "PACKAGE",
      "url": "https://github.com/ZcashFoundation/zebra"
    },
    {
      "type": "WEB",
      "url": "https://github.com/ZcashFoundation/zebra/releases/tag/v4.4.0"
    }
  ],
  "schema_version": "1.4.0",
  "severity": [
    {
      "score": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N",
      "type": "CVSS_V3"
    },
    {
      "score": "CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:H/VA:N/SC:N/SI:H/SA:N",
      "type": "CVSS_V4"
    }
  ],
  "summary": "Zebra\u0027s Block Validator Undercounts Coinbase and P2SH Sigops"
}

Sightings

Author	Source	Type	Date	Other

Nomenclature

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Not patched: The vulnerability was not observed as successfully patched by the user who reported the sighting.

Detection rules are retrieved from Rulezet.

The MITRE ATT&CK techniques below are AI-generated suggestions, inferred from the description of the vulnerability by the CIRCL/vulnerability-attack-technique-classification-roberta-base model, served locally by ML-Gateway. They have not been verified by an analyst and are provided for guidance only.
The approach is described in our paper Mapping CVEs to MITRE ATT&CK Techniques: A Curated Gold-Set Classifier and the Limits of LLM-Assisted Label Expansion.
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Action not permitted

CVE-2026-44498 (GCVE-0-2026-44498)

FKIE_CVE-2026-44498

GHSA-JV4H-J224-23CC

A: Coinbase Hidden Legacy Sigops

B: Aggregate P2SH Sigops.

Patches

Workarounds

Resources

Tags

Sightings

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Related by attack behaviour