CVE-2020-24240

GNU Bison before 3.7.1 has a use-after-free in obstackfree 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.

References

Affected packages

Git / github.com/akimd/bison

Affected ranges

Type

GIT

Repo

https://github.com/akimd/bison

Events

Introduced

6675d36e2531f2573dcb8944bd9877214677e151

Last affected

6675d36e2531f2573dcb8944bd9877214677e151

Fixed

be95a4fe2951374676efc9454ffee8638faaf68d

Database specific

{
    "source": [
        "CPE_STRING",
        "REFERENCES"
    ],
    "cpe": "cpe:2.3:a:gnu:bison:3.7:*:*:*:*:*:*:*",
    "extracted_events": [
        {
            "introduced": "3.7"
        },
        {
            "last_affected": "3.7"
        }
    ]
}

Affected versions

3.*

3.7

v3.*

v3.7

Database specific

vanir_signatures_modified

"2026-07-08T17:56:40Z"

source

"https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2020-24240.json"

vanir_signatures

[
    {
        "id": "CVE-2020-24240-85d57cd5",
        "digest": {
            "line_hashes": [
                "152892177091449443900596977177214106375",
                "110470093975942762776580447940415453127",
                "8556976720912662219078527567889747895"
            ],
            "threshold": 0.9
        },
        "signature_version": "v1",
        "signature_type": "Line",
        "source": "https://github.com/akimd/bison/commit/be95a4fe2951374676efc9454ffee8638faaf68d",
        "deprecated": false,
        "target": {
            "file": "src/flex-scanner.h"
        }
    }
]