CVE-2021-39537

Exp

An issue was discovered in ncurses through v6.2-1. _nc_captoinfo in captoinfo.c has a heap-based buffer overflow.

Published: 2021-09-20 Last update: 2026-06-17 Assigner: [email protected] Source: [email protected]
NVD Status：Modified，CVE State: published
View at NVD, CVE.org, EUVD

CVE-2021-39537 is rated High Exploit Risk (82.7/100): CVSS High severity, with medium exploitation likelihood (EPSS 3.00%). 1 public exploit reference(s) are indexed (Exploit-DB). EPSS rose +2.50% over the last day, indicating growing attacker interest. Public exploits are available—assess exposure, apply mitigations, and prioritize patching.

Risk is dynamic; we continuously reassess and refresh what is shown on this page as upstream context changes.

Public exploit references (Exploit-DB) for CVE-2021-39537

EDB-ID Source Kind Published Link
— nvd_ref exploit_tag Exploit-DB ↗

Exploit prediction scoring system (EPSS) score for CVE-2021-39537

EPSS lead: Daily EPSS estimates relative likelihood of exploitation; percentile ranks this CVE among scored vulnerabilities (higher = more severe relative rank).

# Date Old EPSS score New EPSS score Delta (New - Old)
1 2026-06-15 0.51% 3.00% +2.50%
2 2026-06-06 0.40% 0.51% +0.11%
3 2025-11-21 — 0.40% —

Full EPSS history (29 records total)

Common vulnerability scoring system (CVSS) metrics for CVE-2021-39537

CVSS metrics for this CVE.

Base score Version Severity Vector Exploitability Impact Score source
8.8 3.1 HIGH
CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/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:R)
A real person has to do something—click, install, enable—otherwise it doesn’t land.
Scope (S:U)
Damage stays in the same “trust bubble” as the broken component—no big spill into unrelated systems.
Confidentiality (C:H)
Serious risk that confidential data gets exposed in a big way.
Integrity (I:H)
They could widely tamper with or forge data—trust in the data is badly hurt.
Availability (A:H)
Could take the service down hard or make it unusable for people who depend on it.
 2.8 5.9 [email protected]
6.8 2.0 MEDIUM
AV:N/AC:M/Au:N/C:P/I:P/A:P Click to expand
Access vector (AV:N)
Can be exploited remotely over network reachability.
Access complexity (AC:M)
Exploitation needs some favorable conditions, but not exceptional ones.
Authentication (AU:N)
No authentication is required.
Confidentiality impact (C:P)
Partial confidentiality impact.
Integrity impact (I:P)
Partial integrity impact.
Availability impact (A:P)
Partial availability impact.
 8.6 6.4 [email protected]

Weakness enumeration for CVE-2021-39537

OS Trackers for CVE-2021-39537

vendor priority summary link
alpine — CVE-2021-39537: 1 source package rows (ncurses); 24 state rows across 9 repos (3.11-main, 3.12-main, 3.17-main, 3.18-main, 3.19-main, 3.20-main, 3.21-main, 3.22-main, edge-main); fixed 8, open 16. https://security.alpinelinux.org/vuln/CVE-2021-39537
debian unimportant CVE-2021-39537 unimportant priority: Debian including 1 source packages (ncurses), 5 status rows across 5 suites (bookworm, bullseye, forky, sid, trixie): resolved 5. https://security-tracker.debian.org/tracker/CVE-2021-39537
redhat low — https://access.redhat.com/security/cve/CVE-2021-39537
suse medium CVE-2021-39537 severity moderate: SUSE including 940 source package names (0.0.17-1.1:libncurses6-6.1-5.9.1, 0.0.17-1.1:terminfo-base-6.1-5.9.1, …), 2630 product×package rows across 606 product lines (Container bci/bci-base-fips, Container bci/bci-init, … (606 product lines)): Fixed 2476, Known Affected 154. https://www.suse.com/security/cve/CVE-2021-39537/
ubuntu negligible CVE-2021-39537 negligible priority: Ubuntu including 1 source packages (ncurses), 10 status rows across 10 suites (bionic, focal, hirsute, impish, jammy, kinetic, lunar, trusty, upstream, xenial): released 5, not-affected 4, ignored 1. https://ubuntu.com/security/CVE-2021-39537

Affected software / configurations for CVE-2021-39537

Vendor Product Version Raw CPE
gnu ncurses <= 6.2.1 cpe:2.3:a:gnu:ncurses:*:*:*:*:*:*:*:*
apple mac_os_x 10.12.6 cpe:2.3:o:apple:mac_os_x:10.12.6:*:*:*:*:*:*:*
apple macos 11.7 cpe:2.3:o:apple:macos:11.7:*:*:*:*:*:*:*
apple macos 13.0 cpe:2.3:o:apple:macos:13.0:*:*:*:*:*:*:*

References for CVE-2021-39537

URL Tags
http://cvsweb.netbsd.org/bsdweb.cgi/pkgsrc/devel/ncurses/patches/patch-ncurses_tinfo_captoinfo.c?rev=1.1&content-type=text/x-cvsweb-markup Patch Third Party Advisory
http://seclists.org/fulldisclosure/2022/Oct/28 Mailing List Third Party Advisory
http://seclists.org/fulldisclosure/2022/Oct/41 Mailing List Third Party Advisory
http://seclists.org/fulldisclosure/2022/Oct/43 Mailing List Third Party Advisory
http://seclists.org/fulldisclosure/2022/Oct/45 Mailing List Third Party Advisory
https://lists.debian.org/debian-lts-announce/2023/12/msg00004.html
https://lists.gnu.org/archive/html/bug-ncurses/2020-08/msg00006.html Exploit Mailing List Vendor Advisory
https://lists.gnu.org/archive/html/bug-ncurses/2021-10/msg00023.html Mailing List Vendor Advisory
https://security.netapp.com/advisory/ntap-20230427-0012/
https://support.apple.com/kb/HT213443 Third Party Advisory
https://support.apple.com/kb/HT213444 Third Party Advisory
https://support.apple.com/kb/HT213488 Third Party Advisory
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