EUVD-2026-39322
GHSA-cmgx-qw5m-5j29
Severity by source
AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H
Local trigger via low-privilege interface manipulation; pure availability impact through deadlock; no confidentiality or integrity effect.
Primary rating from NVD.
CVSS VectorNVD
CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H
Lifecycle Timeline
5DescriptionNVD
In the Linux kernel, the following vulnerability has been resolved:
net: phy: don't try to setup PHY-driven SFP cages when using genphy
We don't have support for PHY-driver SFP cages with the genphy code.
On top of that, it was found by sashiko that running sfp_bus_add_upstream() for genphy deadlocks, as for genphy the PHY probing runs under RTNL, which isn't the case for non-genphy drivers.
This problem was reproduced, and does lead to a deadlock on RTNL.
Before the blamed commit, the phy_sfp_probe() call was made by individual PHY drivers, so there was no way to get to the SFP probing path when using genphy.
Let's therefore only run phy_sfp_probe when not using genphy.
AnalysisAI
Deadlock in the Linux kernel PHY networking subsystem (net/phy) allows a local low-privileged user to freeze the networking stack on systems using the generic PHY driver (genphy) with SFP cage hardware. When genphy triggers PHY probing - which occurs while holding the RTNL lock - it erroneously calls sfp_bus_add_upstream(), which itself attempts to acquire RTNL, producing a self-deadlock confirmed by reproduction. …
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Attack ChainAIDerived
Hypothetical attack flow derived from CVE metadata
Vulnerability AssessmentAI
| Exploitation | All three conditions must be simultaneously present: (1) The affected Linux kernel version (introduced from commit bad869b5e41a08424ff130fd6bb41b854be70095, including 7.1-rc1 through rc7, fixed in 7.0.13 and 7.1) must be running - this is a non-default condition for patched distributions. … Additional conditions and limiting factors are described in the full assessment. |
| Risk Assessment | Real-world exploitation risk is low despite the high availability impact. … Full risk analysis with EPSS, KEV, and SSVC signal comparison available after sign-in. |
| Exploit Scenario | A local operator or low-privileged user on an embedded networking device - such as a managed switch or router - with genphy-driven SFP interfaces triggers interface initialization or reconfiguration (e.g., via 'ip link set up' or network manager). The kernel enters the genphy PHY probing path while holding RTNL and calls sfp_bus_add_upstream(), which blocks waiting for RTNL again. … |
| Remediation | The primary fix is to upgrade the Linux kernel to version 7.0.13 (stable branch) or 7.1 (mainline). … Detailed patch versions, workarounds, and compensating controls in full report. |
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Same weakness CWE-667 – Improper Locking
View allSame technique Information Disclosure
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External POC / Exploit Code
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