In the GNU C Library (aka glibc or libc6) through 2.29, check_dst_limits_calc_pos_1 in posix/regexec.c has Uncontrolled Recursion, as demon…

published 2019-02-26 7 y ago modified 2026-06-17 4 mo ago also EUVD-2018-13339

cvss: 7.5; version 3.0, NVD
cisa kev: Not listed; not in CISA's catalog
epss: 5.8%; EPSS 5.8% chance of exploitation in 30 days, percentile 93%
public exploits: 0; none known

In the GNU C Library (aka glibc or libc6) through 2.29, check_dst_limits_calc_pos_1 in posix/regexec.c has Uncontrolled Recursion, as demonstrated by '(\227|)(\\1\\1|t1|\\\2537)+' in grep.

Patch / fix

links 1

security.netapp.com/advisory/ntap-20190315-0002/ advisory

Vendor advisories

What the vendors themselves say about their products: affected, fixed or not affected, and what to do.

red hat product security vex CVE-2018-20796 updated 2026-11-07 cvss 5.3

glibc: uncontrolled recursion in function check_dst_limits_calc_pos_1 in posix/regexec.c

Red Hat Enterprise Linux 6 nscd, glibc, glibc-utils, glibc-common Red Hat Enterprise Linux 7 nscd, glibc, glibc-utils, glibc-common Red Hat Enterprise Linux 8 nscd, glibc, libnsl, nss_db, nss_hesiod, glibc-utils, +7 more
not affected: vulnerable code not present

Red Hat CSAF VEX © Red Hat, Inc., from https://security.access.redhat.com/data/csaf/v2/vex/; changed: reduced to product statuses and remediations. CC BY 4.0 · csaf

Exploit prediction

5.80% chance of exploitation in the next 30 days, higher than 93% of all scored CVEs (FIRST EPSS, 2026-11-08).

Exploits and checks

lists.gnu.org https://lists.gnu.org/archive/html/bug-gnulib/2019-01/msg00108.html referenced PoC, tagged "exploit" by a source, unverified
debbugs.gnu.org https://debbugs.gnu.org/cgi/bugreport.cgi?bug=34141 referenced PoC, tagged "exploit" by a source, unverified

CVSS scores

assigned by	version	score	vector
NVD	3.0	7.5	CVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
NVD	2.0	5.0	AV:N/AC:L/Au:N/C:N/I:N/A:P

Classification

Weakness

CWE-674 Uncontrolled Recursion

References

security.netapp.com /advisory/ntap-20190315-0002/
patch, third-party-advisory
lists.gnu.org /archive/html/bug-gnulib/2019-01/msg00108.html
exploit, mailing-list, vendor-advisory
debbugs.gnu.org /cgi/bugreport.cgi?bug=34141
exploit, mailing-list, vendor-advisory
securityfocus.com /bid/107160
vdb-entry, third-party-advisory
support.f5.com /csp/article/K26346590?utm_source=f5support&amp%3Butm_medium=RSS

Sources

CVE List CVE-2018-20796
NVD CVE-2018-20796

Fencer Vulns keeps one entry per vulnerability: the CVE id wins, then GHSA, and records that alias each other are merged, except that two CVEs always keep separate entries. The same data is available as JSON.

Summary