Race Condition in GNU Sed_CVE-2026-5958

2.1 / 10

LOW

CVSS:4.0/AV:L/AC:L/AT:P/PR:N/UI:N/VC:N/VI:L/VA:N/SC:N/SI:N/SA:N

Description

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.

Basic Information

ID CVE-2026-5958

Source CERT-PL

Published Apr 20, 2026 at 11:59

Modified Apr 20, 2026 at 12:05

Affected Product

Vendor GNU

Product Sed

Version 4.1e

Affected Versions GNU Sed 4.1e

CWE Classification

CWE-367

References

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    "description": "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: \n1. resolves symlink to its target and stores\u00a0the resolved path for determining when output is written,\n2. opens the original symlink path\u00a0(not the resolved one) to read the file. \nBetween 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.\u00a0This can lead to arbitrary file overwrite with attacker-controlled content in the context of the sed process.\n\n\nThis issue was fixed in version 4.10.",
    "published": "2026-04-20T11:59:32.214Z",
    "modified": "2026-04-20T12:05:22.221Z",
    "type": "cve",
    "title": "Race Condition in GNU Sed",
    "source": "CERT-PL",
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