CVE-2023-26964: An issue was discovered in hyper v0.13.7

This week

HIGH 7.5REMOTEDOWNGRADEDOWNGRADE

CVE-2023-26964 is a high-severity flaw (CVSS 7.5) affecting h2, hyper. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.

An issue was discovered in hyper v0.13.7. h2-0.2.4 Stream stacking occurs when the H2 component processes HTTP2 RST_STREAM frames. As a result, the memory and CPU usage are high which can lead to a Denial of Service (DoS).

Why this priority

High severity
Public exploit reference
Remotely exploitable, no login, no user action

No fix is published yet: follow the downgrade or mitigation steps.

Risk facts

CVSS score	7.5 (High)
Attack vector	Network (remote)
Attack complexity	Low
Privileges needed	None
User interaction	None
EPSS exploit chance	1.1% (top 34%)
CISA exploited list	No
Weakness	CWE-770
Published	2023-04-11
Last modified	2026-06-17

Publisher (CNA): MITRE · Vendor: hyper

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

Am I affected?

Timeline

2023-04-11 14:15 UTCPublished CVE record published
2026-06-17 05:44 UTCUpdated Record last modified

hyper h2 DOWNGRADE

Affected: 0.2.4

Fixed in: no fixed release known

Safe to downgrade to: a release before 0.2.4

1. Check installed version

apt-cache policy h2 || rpm -q h2 || h2 --version

2. No fixed release: DOWNGRADE to a release before 0.2.4 (Debian / Ubuntu)

apt-cache madison h2 sudo apt install h2=<VERSION_BEFORE_0.2.4> sudo apt-mark hold h2

2. No fixed release: DOWNGRADE (RHEL / Amazon Linux / Fedora)

dnf --showduplicates list h2 sudo dnf downgrade h2-<VERSION_BEFORE_0.2.4> sudo dnf versionlock add h2

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.

hyper hyper DOWNGRADE

Affected: 0.13.7

Fixed in: no fixed release known

Safe to downgrade to: a release before 0.13.7

1. Check installed version

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

2. No fixed release: DOWNGRADE to a release before 0.13.7 (Debian / Ubuntu)

apt-cache madison hyper sudo apt install hyper=<VERSION_BEFORE_0.13.7> sudo apt-mark hold hyper

2. No fixed release: DOWNGRADE (RHEL / Amazon Linux / Fedora)

dnf --showduplicates list hyper sudo dnf downgrade hyper-<VERSION_BEFORE_0.13.7> sudo dnf versionlock add hyper

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-2023-26964?

h2: downgrade or apply the listed mitigation; hyper: downgrade or apply the listed mitigation. Exact commands for each OS are on this page.

Is CVE-2023-26964 being exploited?

CVE-2023-26964 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-2023-26964 affect?

CVE-2023-26964 affects h2, hyper. Severity is high (CVSS 7.5). An issue was discovered in hyper v0.13.7. h2-0.2.4 Stream stacking occurs when the H2 component processes HTTP2 RST_STREAM frames. As a result, the memory and CPU usage are high which can lead to a Denial of Service (DoS).

How urgent is CVE-2023-26964?

Priority 53/100. High severity; Public exploit reference; Remotely exploitable, no login, no user action

Related CVEs

CVE-2022-45868 HIGH 8.4 UPGRADE The web-based admin console in H2 Database Engine before 2.2.220 can be started via the CLI with the argument

References

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