CVE-2023-35838: The WireGuard client 0.5.3 on Windows insecurely configures the operating system and firewall such that traffi

Routine

MEDIUM 5.7DOWNGRADE

CVE-2023-35838 is a medium-severity flaw (CVSS 5.7) affecting wireguard. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.

The WireGuard client 0.5.3 on Windows insecurely configures the operating system and firewall such that traffic to a local network that uses non-RFC1918 IP addresses is blocked. This allows an adversary to trick the victim into blocking IP traffic to selected IP addresses and services even while the VPN is enabled. NOTE: the tunnelcrack.mathyvanhoef.com website uses this CVE ID to refer more generally to "LocalNet attack resulting in the blocking

Why this priority

Public exploit reference

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

Risk facts

CVSS score	5.7 (Medium)
Attack vector	Adjacent network
Attack complexity	Low
Privileges needed	None
User interaction	Required
EPSS exploit chance	0.7% (top 47%)
CISA exploited list	No
Weakness	CWE-610
Published	2023-08-09
Last modified	2026-06-17

Publisher (CNA): MITRE · Vendor: wireguard

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

Am I affected?

Timeline

2023-08-09 23:15 UTCPublished CVE record published
2026-06-17 06:05 UTCUpdated Record last modified

wireguard wireguard DOWNGRADE

Affected: 0.5.3

Fixed in: no fixed release known

Safe to downgrade to: a release before 0.5.3

1. Check installed version

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

2. No fixed release: DOWNGRADE to a release before 0.5.3 (Debian / Ubuntu)

apt-cache madison wireguard sudo apt install wireguard=<VERSION_BEFORE_0.5.3> sudo apt-mark hold wireguard

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

dnf --showduplicates list wireguard sudo dnf downgrade wireguard-<VERSION_BEFORE_0.5.3> sudo dnf versionlock add wireguard

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-2023-35838?

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

Is CVE-2023-35838 being exploited?

CVE-2023-35838 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-2023-35838 affect?

CVE-2023-35838 affects wireguard. Severity is medium (CVSS 5.7). The WireGuard client 0.5.3 on Windows insecurely configures the operating system and firewall such that traffic to a local network that uses non-RFC1918 IP addresses is blocked. This allows an adversary to trick the victim into blocking IP

How urgent is CVE-2023-35838?

Priority 38/100. Public exploit reference

Software pages

Windows vulnerabilities · WireGuard vulnerabilities

Related CVEs

CVE-2021-46873 MEDIUM 5.3 DOWNGRADE WireGuard, such as WireGuard 0.5.3 on Windows, does not fully account for the possibility that an adversary mi

References

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