VulnerabilityUndergoing Analysis

CVE-2026-49114

A local attacker with write access to the directory where a victim serializes external data can deterministically pre-plant a symlink that is being followed, causing the victim's write to append to any file the victim can write, e.g.…

MEDIUM 6.8EPSS 0.11%

Does this matter?

Lower severity and a low EPSS score (0.11%). Track it; it rarely justifies an emergency change on its own.

Description

In ONNX before 1.21.0, the 'save_external_data' function builds the external-data file path from the model's external_data location field and opens it for writing without 'O_NOFOLLOW/O_EXCL', after a non-atomic 'os.path.isfile()' check. A local attacker with write access to the directory where a victim serializes external data can deterministically pre-plant a symlink that is being followed, causing the victim's write to append to any file the victim can write, e.g. ~/.ssh/authorized_keys, cron files, or application configs. Fixed in 1.21.0.

CVSS 4.0: 6.8 MEDIUMCVSS:4.0/AV:L/AC:L/AT:N/PR:N/UI:A/VC:N/VI:H/VA:H/SC:N/SI:N/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/M
EPSS: 0.11% probability · 1th percentile
CISA KEV: Not listed
Weakness: CWE-22, CWE-59, CWE-367
Source: 9119a7d8-5eab-497f-8521-727c672e3725

References

Source: NVD record, EPSS from FIRST.org, KEV from CISA. Refreshed daily.