PT-2026-33758 · Gnu · Sed

Marcin Wyczechowski + 1 · Published 2026-04-20 · Updated 2026-04-20 · CVE-2026-5958

NVD

CVSS v4.0

2.1

Low

AV:L/AC:L/AT:P/PR:N/UI:N/VC:N/VI:L/VA:N/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

When sed is invoked with both -i (in-place edit) and --follow-symlinks, the function open next file() performs two separate, non-atomic filesystem operations on the same path:

1. resolves symlink to its target and stores the resolved path for determining when output is written,
2. opens the original symlink path (not the resolved one) to read the file. Between these two calls there is a race window. If an attacker atomically replaces the symlink with a different target during that window, sed will: read content from the new (attacker-chosen) symlink target and write the processed result to the path recorded in step 1. This can lead to arbitrary file overwrite with attacker-controlled content in the context of the sed process.

This issue was fixed in version 4.10.

Fix

Time Of Check To Time Of Use

Weakness Enumeration

CWE-367

Related Identifiers

CVE-2026-5958

Affected Products

Sed

References · 3

• https://nvd.nist.gov/vuln/detail/CVE-2026-5958 · Security Note
• https://cert.pl/en/posts/2026/04/CVE-2026-5958 · Note
• https://gnu.org/software/sed · Note