PatchTheCVECVE-2026-10686: Zephyr's IPv6 forwarding path re-sent routed unicast packets without ever decrementing the IPv6 hop limit
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MEDIUM 5.8REMOTEUPGRADE
CVE-2026-10686 is a medium-severity flaw (CVSS 5.8) affecting zephyr. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.
Zephyr's IPv6 forwarding path re-sent routed unicast packets without ever decrementing the IPv6 hop limit. Both routing branches of ipv6_route_packet() (subsys/net/ip) were affected: the explicit-route path (net_route_packet()) and the on-link cross-interface path (net_route_packet_if()). Each set the packet forwarding flag and called net_send_data() with the hop limit untouched and no expiry check. Per RFC 8200 the hop-limit decrement is the me
Why this priority
- Public exploit reference
- Remotely exploitable, no login, no user action
A fixed release or distro patch exists.
Risk facts
| CVSS score | 5.8 (Medium) |
| Attack vector | Network (remote) |
| Attack complexity | Low |
| Privileges needed | None |
| User interaction | None |
| EPSS exploit chance | 0.5% (top 57%) |
| CISA exploited list | No |
| Weakness | CWE-835 |
| Published | 2026-07-31 |
| Last modified | 2026-10-23 |
Publisher (CNA): Zephyr Project · Vendor: zephyrproject
Am I affected?
Timeline
- Published CVE record published
- Updated Record last modified
zephyrproject zephyr UPGRADE
Affected: >= 1.8.0 and < 4.5.0
Fixed in: 4.5.0
Safe to downgrade to: a release before 1.8.0
Check your OS release
cat /etc/os-release; uname -r
Debian / Ubuntu
sudo apt update && sudo apt full-upgrade
RHEL / Amazon Linux / Fedora
sudo dnf upgrade --refresh
Windows
Install the latest cumulative update from Windows Update
If no patch exists yet
OS downgrades are not safe. Apply the vendor mitigation from the advisory and restrict exposure.
Exact fixes by distribution
Fedora 46 · kwin-zones · FIXED · 1.0.13-1.fc46 · FEDORA-2026-95888f332b · source
sudo dnf upgrade --advisory=FEDORA-2026-95888f332b
Fedora ELN · nginx-mod-brotli · FIXED · 1.0.0~rc-16.eln159 · FEDORA-2026-501a6a8273 · source
sudo dnf upgrade --advisory=FEDORA-2026-501a6a8273
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.
Scores and fixes here are computed automatically from those and other public sources. Confirm with the vendor advisory before changing production systems.
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