CVE-2020-23856

Use-after-Free vulnerability in cflow 1.6 in the void call(char *name, int line) function at src...

5.5 MediumFix available

Use-after-Free vulnerability in cflow 1.6 in the void call(char *name, int line) function at src/parser.c, which could cause a denial of service via the pointer variable caller->callee.

Attack profile

How easy it is to exploit

Attack vector: Local
Complexity: Low
Privileges needed: Low
User interaction: None

What an attacker can affect

Confidentiality: None
Integrity: None
Availability: High

Exploit likelihood

0.42%Down 0.4 points since May 19, 2021

What each source reports

NVD Score used 5.5

Use-after-Free vulnerability in cflow 1.6 in the void call(char *name, int line) function at src/parser.c, which could cause a denial of service via the pointer variable caller->callee.

Record: CVE-2020-23856
CVSS 3.1: 5.5 MediumCVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H
CVSS 2.0: 2.1 LowAV:L/AC:L/Au:N/C:N/I:N/A:P
Weakness: CWE-416
Updated: 2026-11-02

CVE List No score

Use-after-Free vulnerability in cflow 1.6 in the void call(char *name, int line) function at src/parser.c, which could cause a denial of service via the pointer variable caller->callee.

Record: CVE-2020-23856
Updated: 2026-11-02

EUVDEUVD-2020-16593 No score

Use-after-Free vulnerability in cflow 1.6 in the void call(char *name, int line) function at src/parser.c, which could cause a denial of service via the pointer variable caller->callee.

Record: EUVD-2020-16593
Updated: 2026-11-03

GitHub AdvisoriesGHSA-h5qf-rf3c-vmj5 No score

Use-after-Free vulnerability in cflow 1.6 in the void call(char *name, int line) function at src...

Use-after-Free vulnerability in cflow 1.6 in the void call(char *name, int line) function at src/parser.c, which could cause a denial of service via the pointer variable caller->callee.

Record: GHSA-h5qf-rf3c-vmj5
Weakness: CWE-416
Updated: 2026-11-02

OSV 5.5

Use-after-Free vulnerability in cflow 1.6 in the void call(char *name, int line) function at src/parser.c, which could cause a denial of service via the pointer variable caller->callee.

Record: CVE-2020-23856
CVSS 3.1: 5.5 MediumCVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H
Updated: 2026-11-02

OSVDEBIAN-CVE-2020-23856 5.5

Use-after-Free vulnerability in cflow 1.6 in the void call(char *name, int line) function at src/parser.c, which could cause a denial of service via the pointer variable caller->callee.

Record: DEBIAN-CVE-2020-23856
CVSS 3.1: 5.5 MediumCVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H
Updated: 2026-11-02

OSVUBUNTU-CVE-2020-23856 5.5

Use-after-Free vulnerability in cflow 1.6 in the void call(char *name, int line) function at src/parser.c, which could cause a denial of service via the pointer variable caller->callee.

Record: UBUNTU-CVE-2020-23856
CVSS 3.1: 5.5 MediumCVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H
Updated: 2026-11-02

Affected products

Affected packages

Affected packages
Package	Affected	Fixed
`cflow` Debian:12	before 1:1.6-6	1:1.6-6
`cflow` Debian:13	before 1:1.6-6	1:1.6-6
`cflow` Debian:14	before 1:1.6-6	1:1.6-6
`cflow` Ubuntu:Pro:16.04:LTS	All versions, plus listed versions 1:1.4+dfsg1-3ubuntu11:1.4+dfsg1-3ubuntu1.16.04.1~esm1	None known
`cflow` Ubuntu:Pro:18.04:LTS	All versions, plus listed versions 1:1.4+dfsg1-3ubuntu11:1.4+dfsg1-3ubuntu1.18.04.1~esm1	None known
`cflow` Ubuntu:20.04:LTS	All versions, plus listed versions 1:1.6-4	None known
`cflow` Ubuntu:22.04:LTS	All versions, plus listed versions 1:1.6-41:1.6-61:1.7-2	None known
`cflow` Ubuntu:24.04:LTS	All versions, plus listed versions 1:1.7-41:1.7-5	None known
`cflow` Ubuntu:25.10	All versions, plus listed versions 1:1.7-51:1.8-1	None known
`cflow` Ubuntu:26.10	All versions, plus listed versions 1:1.8-1build1	None known
`cflow` Ubuntu:26.04:LTS	All versions, plus listed versions 1:1.8-11:1.8-1build1	None known

History

History
Recorded	Changed	Sources
Nov 3, 2026	aliases	EUVD
Nov 2, 2026	first indexed	CVE List, GitHub Advisories, NVD, OSV

Dates are when Every CVE recorded each change. Upstream dates may differ.

In short

CVE-2020-23856 is a medium vulnerability (CVSS 5.5) in Gnu Cflow, published May 18, 2021. No source lists public exploit code. EPSS puts the chance of exploitation in the next 30 days at 0.42%, the 36th percentile. Fixed in cflow 1:1.6-6.

References

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