CVE-2019-11636: Zcash 2.x allows an inexpensive approach to "fill all transactions of all blocks" and "prevent any real transa

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HIGH 7.5REMOTEUPGRADE

CVE-2019-11636 is a high-severity flaw (CVSS 7.5) affecting zcash. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.

Zcash 2.x allows an inexpensive approach to "fill all transactions of all blocks" and "prevent any real transaction from occurring" via a "Sapling Wood-Chipper" attack.

Why this priority

High severity
Remotely exploitable, no login, no user action

A fixed release or distro patch exists.

Risk facts

CVSS score	7.5 (High)
Attack vector	Network (remote)
Attack complexity	Low
Privileges needed	None
User interaction	None
EPSS exploit chance	2.2% (top 18%)
CISA exploited list	No
Weakness	CWE-254
Published	2019-05-01
Last modified	2026-06-17

Publisher (CNA): MITRE · Vendor: z.cash

Last updated 2026-06-17 · Sources: CVE Program, NVD, CISA KEV, EPSS and vendor advisories · How we score

Am I affected?

Timeline

2019-05-01 17:29 UTCPublished CVE record published
2026-06-17 02:13 UTCUpdated Record last modified

z.cash zcash UPGRADE

Affected: >= 2.0.0 and <= 2.0.4 · 2.0.5 rc1

Fixed in: newer than 2.0.4

Safe to downgrade to: a release before 2.0.0

1. Check installed version

apt-cache policy zcash || rpm -q zcash || zcash --version

2. UPGRADE to newer than 2.0.4 (Debian / Ubuntu)

sudo apt update && sudo apt install --only-upgrade zcash

2. UPGRADE (RHEL / Amazon Linux / Fedora)

sudo dnf upgrade zcash

Note

Distros often backport fixes without changing the version number. Confirm with the distro advisory or changelog.

3. If no update is available yet, DOWNGRADE to a release before 2.0.0 (Debian / Ubuntu)

apt-cache madison zcash sudo apt install zcash=<VERSION_BEFORE_2.0.0> sudo apt-mark hold zcash

3. If no update is available yet, DOWNGRADE (RHEL / Amazon Linux / Fedora)

dnf --showduplicates list zcash sudo dnf downgrade zcash-<VERSION_BEFORE_2.0.0> sudo dnf versionlock add zcash

Downgrade risk

Downgrading can break dependent software and may reopen older bugs. Read the distro advisory first and test on a non-production host.

After downgrade

Restart the service, and keep the package held until a fixed release ships.

Verify at the official source NVD · CVE Program · Report a problem with this page
Scores and fixes here are computed automatically from those and other public sources. Confirm with the vendor advisory before changing production systems.

Quick answers

How do I fix CVE-2019-11636?

zcash: upgrade to newer than 2.0.4. Exact commands for each OS are on this page.

Is CVE-2019-11636 being exploited?

CVE-2019-11636 is not on the CISA Known Exploited Vulnerabilities list at the time of the last update. Check again, as this can change.

What does CVE-2019-11636 affect?

CVE-2019-11636 affects zcash. Severity is high (CVSS 7.5). Zcash 2.x allows an inexpensive approach to "fill all transactions of all blocks" and "prevent any real transaction from occurring" via a "Sapling Wood-Chipper" attack.

How urgent is CVE-2019-11636?

Priority 52/100. High severity; Remotely exploitable, no login, no user action

Related CVEs

CVE-2019-7167 HIGH 7.5 UPGRADE Zcash, before the Sapling network upgrade (2018-10-28), had a counterfeiting vulnerability
CVE-2019-16930 MEDIUM 5.3 UPGRADE Zcashd in Zcash before 2.0.7-3 allows discovery of the IP address of a full node that owns a shielded address,

References

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