CVE-2023-31147 [Medium] | Security Vulnerability in C-Ares

c-ares is an asynchronous resolver library. When /dev/urandom or RtlGenRandom() are unavailable, c-ares uses rand() to generate random numbers used for DNS query ids. This is not a CSPRNG, and it is also not seeded by srand() so will generate predictable output. Input from the random number generator is fed into a non-compilant RC4 implementation and may not be as strong as the original RC4 implementation. No attempt is made to look for modern OS-provided CSPRNGs like arc4random() that is widely available. This issue has been fixed in version 1.19.1.

#	Date	Old EPSS score	New EPSS score	Delta (New - Old)
1	2026-06-15	0.09%	0.91%	+0.82%
2	2025-11-21	0.33%	0.09%	-0.24%
3	2025-11-18	—	0.33%	—

Date

Old EPSS score

New EPSS score

Delta (New - Old)

2026-06-15

0.09%

0.91%

+0.82%

2025-11-21

0.33%

0.09%

-0.24%

2025-11-18

—

0.33%

—

Base score	Version	Severity	Vector	Exploitability	Impact	Score source
5.9	3.1	MEDIUM	`CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:H/A:N` 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:H) Even with access, the exploit needs extra luck, timing, or a fussy environment to actually work. 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:H) They could widely tamper with or forge data—trust in the data is badly hurt. Availability (A:N) Service keeps running; no real outage angle.	2.2	3.6	[email protected]
6.5	3.1	MEDIUM	`CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:L/A:N` 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:L) Some sensitive info could get out, but not a total data dump. Integrity (I:L) Attackers could change some data, but it’s limited—not everything goes. Availability (A:N) Service keeps running; no real outage angle.	3.9	2.5	[email protected]

Base score

Version

Severity

Vector

Exploitability

Impact

Score source

5.9

3.1

MEDIUM

CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:H/A:N 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:H): Even with access, the exploit needs extra luck, timing, or a fussy environment to actually work.
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:H): They could widely tamper with or forge data—trust in the data is badly hurt.
Availability (A:N): Service keeps running; no real outage angle.

2.2

3.6

[email protected]

6.5

3.1

MEDIUM

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:L/A:N 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:L): Some sensitive info could get out, but not a total data dump.
Integrity (I:L): Attackers could change some data, but it’s limited—not everything goes.
Availability (A:N): Service keeps running; no real outage angle.

3.9

2.5

[email protected]

OS Trackers for CVE-2023-31147

vendor	priority	summary	link
`alpine`	medium	CVE-2023-31147: 1 source package rows (c-ares); 5 state rows across 5 repos (3.19-main, 3.20-main, 3.21-main, 3.22-main, edge-main); fixed 0, open 5.	https://security.alpinelinux.org/vuln/CVE-2023-31147
`debian`	unimportant	CVE-2023-31147 unimportant priority: Debian including 1 source packages (c-ares), 5 status rows across 5 suites (bookworm, bullseye, forky, sid, trixie): resolved 3, open 2.	https://security-tracker.debian.org/tracker/CVE-2023-31147
`gentoo`	normal	CVE-2023-31147: 1 GLSA(s) (202310-09), 1 atom(s) (net-dns/c-ares); latest impact normal.	https://bugs.gentoo.org/buglist.cgi?quicksearch=CVE-2023-31147
`redhat`	medium	—	https://access.redhat.com/security/cve/CVE-2023-31147
`suse`	medium	CVE-2023-31147 severity moderate: SUSE including 305 source package names (0.3.2-1.2:libcares2-1.19.1-150000.3.23.1, 0.3.32-3.4:libcares2-1.19.1-150000.3.23.1, …), 690 product×package rows across 317 product lines (Container bci/nodejs, Container caasp/v4/cilium, … (317 product lines)): Fixed 538, Known Affected 152.	https://www.suse.com/security/cve/CVE-2023-31147/
`ubuntu`	negligible	CVE-2023-31147 negligible priority: Ubuntu including 1 source packages (c-ares), 8 status rows across 8 suites (bionic, focal, jammy, kinetic, lunar, trusty, upstream, xenial): not-affected 6, ignored 1, released 1.	https://ubuntu.com/security/CVE-2023-31147

Affected software / configurations for CVE-2023-31147

Vendor	Product	Version	Raw CPE
c-ares_project	c-ares	< 1.19.1	cpe:2.3:a:c-ares_project:c-ares::::::::
fedoraproject	fedora	37	cpe:2.3:o:fedoraproject:fedora:37:::::::*
fedoraproject	fedora	38	cpe:2.3:o:fedoraproject:fedora:38:::::::*

References for CVE-2023-31147

URL	Tags
https://github.com/c-ares/c-ares/releases/tag/cares-1_19_1	Release Notes
https://github.com/c-ares/c-ares/security/advisories/GHSA-8r8p-23f3-64c2	Third Party Advisory
https://lists.fedoraproject.org/archives/list/[email protected]/message/B5Z5XFNXTNPTCBBVXFDNZQVLLIE6VRBY/	Mailing List Third Party Advisory
https://lists.fedoraproject.org/archives/list/[email protected]/message/UBFWILTA33LOSV23P44FGTQQIDRJHIY7/	Mailing List Third Party Advisory
https://security.gentoo.org/glsa/202310-09	Third Party Advisory

URL

CVE-2023-31147 | Insufficient randomness in generation of DNS query IDs in c-ares

Exploit prediction scoring system (EPSS) score for CVE-2023-31147

Common vulnerability scoring system (CVSS) metrics for CVE-2023-31147

Weakness enumeration for CVE-2023-31147

OS Trackers for CVE-2023-31147

Affected software / configurations for CVE-2023-31147

References for CVE-2023-31147