CVE-2026-26994: uTLS is a fork of crypto/tls, created to customize ClientHello for fingerprinting resistance while still using

Q: How do I fix CVE-2026-26994?

utls: upgrade to 1.7.0. Exact commands for each OS are on this page.

Q: Is CVE-2026-26994 being exploited?

CVE-2026-26994 is not on the CISA Known Exploited Vulnerabilities list at the time of the last update. Check again, as this can change.

Q: What does CVE-2026-26994 affect?

CVE-2026-26994 affects utls. Severity is medium (CVSS 6.5). uTLS is a fork of crypto/tls, created to customize ClientHello for fingerprinting resistance while still using it for the handshake. In versions 1.6.7 and below, uTLS did not implement the TLS 1.3 downgrade protection mechanism specified in

Q: How urgent is CVE-2026-26994?

Priority 33/100. Remotely exploitable, no login, no user action

Routine

MEDIUM 6.5REMOTEUPGRADE

CVE-2026-26994 is a medium-severity flaw (CVSS 6.5) affecting utls. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.

uTLS is a fork of crypto/tls, created to customize ClientHello for fingerprinting resistance while still using it for the handshake. In versions 1.6.7 and below, uTLS did not implement the TLS 1.3 downgrade protection mechanism specified in RFC 8446 Section 4.1.3 when using a uTLS ClientHello spec. This allowed an active network adversary to downgrade TLS 1.3 connections initiated by a uTLS client to a lower TLS version (e.g., TLS 1.2) by modifyi

Why this priority

Remotely exploitable, no login, no user action

A fixed release or distro patch exists.

Risk facts

CVSS score	6.5 (Medium)
Attack vector	Network (remote)
Attack complexity	Low
Privileges needed	None
User interaction	None
EPSS exploit chance	0.3% (top 77%)
CISA exploited list	No
Weakness	CWE-693
Published	2026-02-20
Last modified	2026-06-17

Publisher (CNA): GitHub, Inc. · Vendor: refraction-networking

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

Am I affected?

Timeline

2026-02-20 03:16 UTCPublished CVE record published
2026-06-17 10:26 UTCUpdated Record last modified

refraction-networking utls UPGRADE

Affected: < 1.7.0

Fixed in: 1.7.0

Safe to downgrade to: no unaffected older release

1. Check installed version

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

2. UPGRADE to 1.7.0 (Debian / Ubuntu)

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

2. UPGRADE (RHEL / Amazon Linux / Fedora)

sudo dnf upgrade utls

Note

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

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-2026-26994?

utls: upgrade to 1.7.0. Exact commands for each OS are on this page.

Is CVE-2026-26994 being exploited?

CVE-2026-26994 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-2026-26994 affect?

CVE-2026-26994 affects utls. Severity is medium (CVSS 6.5). uTLS is a fork of crypto/tls, created to customize ClientHello for fingerprinting resistance while still using it for the handshake. In versions 1.6.7 and below, uTLS did not implement the TLS 1.3 downgrade protection mechanism specified in

How urgent is CVE-2026-26994?

Priority 33/100. Remotely exploitable, no login, no user action

Related CVEs

CVE-2026-27017 MEDIUM 5.3 UPGRADE uTLS is a fork of crypto/tls, created to customize ClientHello for fingerprinting resistance while still using

References

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