CVE-2026-49114

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 v4.0

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/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X

CVSS v3.1

7.1 HIGHCVSS:3.1/AV:L/AC:L/PR:N/UI:R/S:U/C:N/I:H/A:H

EPSS

0.11% chance of exploitation in the next 30 days, 1th percentile

Published

2026-08-21

Proof-of-concept exploits (1)

• onnx/onnx/security/advisories/GHSA-q56x-g2fj-4rj6

References

• CVE Record
• NVD entry

Related

• CVE-2022-25882
• CVE-2025-51480
• CVE-2026-14647
• CVE-2026-49105
• CVE-2026-49127
• CVE-2026-49104