GNU Bison before 3.7.1 has a use-after-free in _obstack_free in lib/obstack.c (called from gram_lex) when a '\0' byte is encountered. NOTE: there is a risk only if Bison is used with untrusted input, and the observed bug happens to cause unsafe behavior with a specific compiler/architecture. The bug report was intended to show that a crash may occur in Bison itself, not that a crash may occur in code that is generated by Bison.

The Unity Linux 20 host has a package installed that is affected by a vulnerability as referenced in the UTSA-2026-093642 advisory.

    GNU Bison before 3.7.1 has a use-after-free in _obstack_free in lib/obstack.c (called from gram_lex) when     a '\0' byte is encountered. NOTE: there is a risk only if Bison is used with untrusted input, and the     observed bug happens to cause unsafe behavior with a specific compiler/architecture. The bug report was     intended to show that a crash may occur in Bison itself, not that a crash may occur in code that is     generated by Bison.

Tenable has extracted the preceding description block directly from the Unity Linux 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.

  - GNU Bison before 3.7.1 has a use-after-free in _obstack_free in lib/obstack.c (called from gram_lex) when     a '\0' byte is encountered. NOTE: there is a risk only if Bison is used with untrusted input, and the     observed bug happens to cause unsafe behavior with a specific compiler/architecture. The bug report was     intended to show that a crash may occur in Bison itself, not that a crash may occur in code that is     generated by Bison. (CVE-2020-24240)

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

There are packages installed that are affected by a vulnerability referenced in the following CVE:

  - GNU Bison before 3.7.1 has a use-after-free in _obstack_free in lib/obstack.c (called from gram_lex) when
    a '\0' byte is encountered. NOTE: there is a risk only if Bison is used with untrusted input, and the
    observed bug happens to cause unsafe behavior with a specific compiler/architecture. The bug report was
    intended to show that a crash may occur in Bison itself, not that a crash may occur in code that is
    generated by Bison. (CVE-2020-24240)

According to the versions of the bison packages installed, the EulerOS installation on the remote host is affected by the following vulnerabilities :

  - GNU Bison before 3.7.1 has a use-after-free in _obstack_free in lib/obstack.c (called from gram_lex) when     a '\0' byte is encountered. NOTE: there is a risk only if Bison is used with untrusted input, and the     observed bug happens to cause unsafe behavior with a specific compiler/architecture. The bug report was     intended to show that a crash may occur in Bison itself, not that a crash may occur in code that is     generated by Bison. (CVE-2020-24240)

Note that Tenable Network Security has extracted the preceding description block directly from the EulerOS security advisory. Tenable has attempted to automatically clean and format it as much as possible without introducing additional issues.

ID	Name	Product	Family	Type	Severity
340579	Unity Linux 20.1050e / 20.1060e / 20.1070e Security Update: bison (UTSA-2026-093642)	Nessus	Unity Linux Local Security Checks	Local	medium
255411	Linux Distros Unpatched Vulnerability : CVE-2020-24240	Nessus	Misc.	Local	medium
423717	Alpine: multiple bison packages: security update to 3.7.2-r0	Tenable Cloud Security	Alpine Linux Local Security Checks	Local	medium
423717	Alpine: multiple bison packages: security update to 3.7.2-r0	Tenable Self-Hosted Container Security	Alpine Linux Local Security Checks	Local	medium
403691	Alpine: multiple bison packages: security update to 3.7.2-r0	Tenable Cloud Security	Alpine Linux Local Security Checks	Local	medium
403691	Alpine: multiple bison packages: security update to 3.7.2-r0	Tenable Self-Hosted Container Security	Alpine Linux Local Security Checks	Local	medium
166844	EulerOS 2.0 SP10 : bison (EulerOS-SA-2022-2674)	Nessus	Huawei Local Security Checks	Local	medium
166837	EulerOS 2.0 SP10 : bison (EulerOS-SA-2022-2642)	Nessus	Huawei Local Security Checks	Local	medium

Detections

Analytics

CVE-2020-24240

medium

Tenable Plugins

medium

medium

medium

medium

medium

medium

medium

medium