Debian Security Advisory

DLA-2431-2 libonig -- LTS security update

Date Reported:
30 Jan 2021
Affected Packages:
Security database references:
In Mitre's CVE dictionary: CVE-2020-26159.
More information:

It was discovered that CVE-2020-26159 in the Oniguruma regular expressions library, notably used in PHP mbstring, was a false-positive. In consequence the patch for CVE-2020-26159 was reverted. For reference, the original advisory text follows.

  • CVE-2020-26159

    In Oniguruma an attacker able to supply a regular expression for compilation may be able to overflow a buffer by one byte in concat_opt_exact_str in src/regcomp.c

For Debian 9 stretch, this problem has been fixed in version 6.1.3-2+deb9u2.

We recommend that you upgrade your libonig packages.

For the detailed security status of libonig please refer to its security tracker page at:

Further information about Debian LTS security advisories, how to apply these updates to your system and frequently asked questions can be found at: