CVE-2020-29573 [High] | Out-of-bounds Write in Glibc

sysdeps/i386/ldbl2mpn.c in the GNU C Library (aka glibc or libc6) before 2.23 on x86 targets has a stack-based buffer overflow if the input to any of the printf family of functions is an 80-bit long double with a non-canonical bit pattern, as seen when passing a \x00\x04\x00\x00\x00\x00\x00\x00\x00\x04 value to sprintf. NOTE: the issue does not affect glibc by default in 2016 or later (i.e., 2.23 or later) because of commits made in 2015 for inlining of C99 math functions through use of GCC built-ins. In other words, the reference to 2.23 is intentional despite the mention of "Fixed for glibc 2.33" in the 26649 reference.

#	Date	Old EPSS score	New EPSS score	Delta (New - Old)
1	2026-06-15	0.16%	2.77%	+2.60%
2	2026-03-03	0.10%	0.16%	+0.06%
3	2025-11-21	—	0.10%	—

Date

Old EPSS score

New EPSS score

Delta (New - Old)

2026-06-15

0.16%

2.77%

+2.60%

2026-03-03

0.10%

0.16%

+0.06%

2025-11-21

—

0.10%

—

Base score	Version	Severity	Vector	Exploitability	Impact	Score source
7.5	3.1	HIGH	`CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H` Click to expand Attack vector (AV:N) Could be attacked over the internet or any normal routed network—not just someone sitting at the machine. Attack complexity (AC:L) Once they can reach the bug, pulling it off is straightforward—no weird race conditions or rare setup. Privileges required (PR:N) No account or special rights needed—anonymous or random user is enough. User interaction (UI:N) Nobody has to click “OK” or open a trap file; it can work without a victim helping. Scope (S:U) Damage stays in the same “trust bubble” as the broken component—no big spill into unrelated systems. Confidentiality (C:N) Doesn’t really leak secrets in a meaningful way. Integrity (I:N) Data isn’t meaningfully altered or forged. Availability (A:H) Could take the service down hard or make it unusable for people who depend on it.	3.9	3.6	[email protected]
5.0	2.0	MEDIUM	`AV:N/AC:L/Au:N/C:N/I:N/A:P` Click to expand Access vector (AV:N) Can be exploited remotely over network reachability. Access complexity (AC:L) Exploitation conditions are straightforward and predictable. Authentication (AU:N) No authentication is required. Confidentiality impact (C:N) No confidentiality impact. Integrity impact (I:N) No integrity impact. Availability impact (A:P) Partial availability impact.	10.0	2.9	[email protected]

Base score

Version

Severity

Vector

Exploitability

Impact

Score source

7.5

3.1

HIGH

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H Click to expand

Attack vector (AV:N): Could be attacked over the internet or any normal routed network—not just someone sitting at the machine.
Attack complexity (AC:L): Once they can reach the bug, pulling it off is straightforward—no weird race conditions or rare setup.
Privileges required (PR:N): No account or special rights needed—anonymous or random user is enough.
User interaction (UI:N): Nobody has to click “OK” or open a trap file; it can work without a victim helping.
Scope (S:U): Damage stays in the same “trust bubble” as the broken component—no big spill into unrelated systems.
Confidentiality (C:N): Doesn’t really leak secrets in a meaningful way.
Integrity (I:N): Data isn’t meaningfully altered or forged.
Availability (A:H): Could take the service down hard or make it unusable for people who depend on it.

3.9

3.6

[email protected]

5.0

2.0

MEDIUM

AV:N/AC:L/Au:N/C:N/I:N/A:P Click to expand

Access vector (AV:N): Can be exploited remotely over network reachability.
Access complexity (AC:L): Exploitation conditions are straightforward and predictable.
Authentication (AU:N): No authentication is required.
Confidentiality impact (C:N): No confidentiality impact.
Integrity impact (I:N): No integrity impact.
Availability impact (A:P): Partial availability impact.

10.0

2.9

[email protected]

OS Trackers for CVE-2020-29573

vendor	priority	summary	link
`debian`	not yet assigned	CVE-2020-29573 not yet assigned priority: Debian including 1 source packages (glibc), 5 status rows across 5 suites (bookworm, bullseye, forky, sid, trixie): resolved 5.	https://security-tracker.debian.org/tracker/CVE-2020-29573
`gentoo`	normal	CVE-2020-29573: 1 GLSA(s) (202101-20), 1 atom(s) (sys-libs/glibc); latest impact normal.	https://bugs.gentoo.org/buglist.cgi?quicksearch=CVE-2020-29573
`redhat`	medium	—	https://access.redhat.com/security/cve/CVE-2020-29573
`suse`	high	CVE-2020-29573 severity important: SUSE including 504 source package names (0.1.0:glibc-2.26-13.56.1, 0.1.75:glibc-2.26-13.56.1, …), 945 product×package rows across 136 product lines (Container caasp/v4/389-ds, Container caasp/v4/busybox, … (136 product lines)): Fixed 799, Known Affected 130, Known Not Affected 16.	https://www.suse.com/security/cve/CVE-2020-29573/
`ubuntu`	low	CVE-2020-29573 low priority: Ubuntu including 2 source packages (eglibc, glibc), 32 status rows across 16 suites (bionic, focal, groovy, hirsute, impish, jammy, kinetic, lunar, mantic, noble, oracular, plucky, questing, trusty, upstream, xenial): DNE 15, not-affected 14, needs-triage 2, needed 1.	https://ubuntu.com/security/CVE-2020-29573

Affected software / configurations for CVE-2020-29573

Vendor	Product	Version	Raw CPE
gnu	glibc	< 2.23	cpe:2.3:a:gnu:glibc:::::::x86:*
redhat	enterprise_linux	7.0	cpe:2.3:o:redhat:enterprise_linux:7.0:::::::*
netapp	cloud_backup	—	cpe:2.3:a:netapp:cloud_backup:-:::::::*
netapp	solidfire_baseboard_management_controller	—	cpe:2.3:h:netapp:solidfire_baseboard_management_controller:-:::::::*

References for CVE-2020-29573

URL	Tags
https://security.gentoo.org/glsa/202101-20	Third Party Advisory
https://security.netapp.com/advisory/ntap-20210122-0004/	Third Party Advisory
https://sourceware.org/bugzilla/show_bug.cgi?id=26649	Issue Tracking Patch Third Party Advisory
https://sourceware.org/pipermail/libc-alpha/2020-September/117779.html	Patch Third Party Advisory

URL

CVE-2020-29573

Exploit prediction scoring system (EPSS) score for CVE-2020-29573

Common vulnerability scoring system (CVSS) metrics for CVE-2020-29573

Weakness enumeration for CVE-2020-29573

OS Trackers for CVE-2020-29573

Affected software / configurations for CVE-2020-29573

References for CVE-2020-29573