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.

The remote SUSE Linux SLES12 host has packages installed that are affected by a vulnerability as referenced in the SUSE- SU-2026:1699-1 advisory.

    This update for sed fixes the following issue:

    - CVE-2026-5958: a TOCTOU race can allow to read attacker-controlled content and write it to an unintended     file (bsc#1262144).

Tenable has extracted the preceding description block directly from the SUSE security advisory.

Note that Nessus has not tested for this issue but has instead relied only on the application's self-reported version number.

The remote Ubuntu 22.04 LTS / 24.04 LTS / 25.10 / 26.04 LTS host has a package installed that is affected by a vulnerability as referenced in the USN-8229-1 advisory.

    Micha Majchrowicz and Marcin Wyczechowski discovered that sed incorrectly handled symbolic links when     performing in-place edits. A local attacker could possibly use this issue to overwrite arbitrary files.

Tenable has extracted the preceding description block directly from the Ubuntu security advisory.

Note that Nessus has not tested for this issue but has instead relied only on the application's self-reported version number.

The Linux/Unix host has one or more packages installed that are impacted by a vulnerability without a vendor supplied patch available.

  - 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. (CVE-2026-5958)

Note that Nessus relies on the presence of the package as reported by the vendor.

ID	Name	Product	Family	Severity
313651	SUSE SLES12 Security Update : sed (SUSE-SU-2026:1699-1)	Nessus	SuSE Local Security Checks	low
312297	Ubuntu 22.04 LTS / 24.04 LTS / 25.10 / 26.04 LTS : sed vulnerability (USN-8229-1)	Nessus	Ubuntu Local Security Checks	low
307651	Linux Distros Unpatched Vulnerability : CVE-2026-5958	Nessus	Misc.	low

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