Use-after-free in GNU Bison - CVE-2020-24240
Published: August 25, 2020 / Updated: September 7, 2020
Vulnerability identifier: #VU46310
CSH Severity: Medium
CVSS v4: 6.9 [CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:A/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N]
CVE-ID: CVE-2020-24240
CWE-ID: CWE-416
Exploitation vector: Remote access
Exploit availability:
No public exploit available
Vulnerability details
The vulnerability allows a remote non-authenticated attacker to perform a denial of service (DoS) attack.
GNU Bison before 3.7.1 has a use-after-free in _obstack_free in lib/obstack.c (called from gram_lex) when a '�' 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.
Affected software
GNU Bison
bison (Alpine package)
bison
bison-debuginfo
bison-debugsource
bison-lang
bison-devel
bison-help
openEuler
bison (Alpine package)
bison
bison-debuginfo
bison-debugsource
bison-lang
bison-devel
bison-help
openEuler
How to mitigate CVE-2020-24240
Install update from vendor's website.
GNU Bison - update to 3.7.1
bison (Alpine package) - update to 3.7.2-r0
bison - update to 3.6.4-2
bison-debuginfo - update to 3.6.4-2
bison-debugsource - update to 3.6.4-2
bison-lang - update to 3.6.4-2
bison-devel - update to 3.6.4-2
bison-help - update to 3.6.4-2
bison (Alpine package) - update to 3.7.2-r0
bison - update to 3.6.4-2
bison-debuginfo - update to 3.6.4-2
bison-debugsource - update to 3.6.4-2
bison-lang - update to 3.6.4-2
bison-devel - update to 3.6.4-2
bison-help - update to 3.6.4-2