CVE-2016-8616 [Low] | Security Vulnerability in Curl

A flaw was found in curl before version 7.51.0 When re-using a connection, curl was doing case insensitive comparisons of user name and password with the existing connections. This means that if an unused connection with proper credentials exists for a protocol that has connection-scoped credentials, an attacker can cause that connection to be reused if s/he knows the case-insensitive version of the correct password.

#	Date	Old EPSS score	New EPSS score	Delta (New - Old)
1	2026-05-30	4.19%	4.51%	+0.32%
2	2026-05-03	4.13%	4.19%	+0.06%
3	2026-03-15	—	4.13%	—

Date

Old EPSS score

New EPSS score

Delta (New - Old)

2026-05-30

4.19%

4.51%

+0.32%

2026-05-03

4.13%

4.19%

+0.06%

2026-03-15

—

4.13%

—

Base score	Version	Severity	Vector	Exploitability	Impact	Score source
3.7	3.0	LOW	`CVSS:3.0/AV:N/AC:H/PR:N/UI:N/S:U/C:N/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: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:L) Attackers could change some data, but it’s limited—not everything goes. Availability (A:N) Service keeps running; no real outage angle.	2.2	1.4	[email protected]
5.9	3.0	MEDIUM	`CVSS:3.0/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]
4.3	2.0	MEDIUM	`AV:N/AC:M/Au:N/C:N/I:P/A:N` 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:N) No confidentiality impact. Integrity impact (I:P) Partial integrity impact. Availability impact (A:N) No availability impact.	8.6	2.9	[email protected]

Base score

Version

Severity

Vector

Exploitability

Impact

Score source

3.7

3.0

LOW

CVSS:3.0/AV:N/AC:H/PR:N/UI:N/S:U/C:N/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: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:L): Attackers could change some data, but it’s limited—not everything goes.
Availability (A:N): Service keeps running; no real outage angle.

2.2

1.4

[email protected]

5.9

3.0

MEDIUM

CVSS:3.0/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]

4.3

2.0

MEDIUM

AV:N/AC:M/Au:N/C:N/I:P/A:N 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:N): No confidentiality impact.
Integrity impact (I:P): Partial integrity impact.
Availability impact (A:N): No availability impact.

8.6

2.9

[email protected]

OS Trackers for CVE-2016-8616

vendor	priority	summary	link
`alpine`	—	CVE-2016-8616: 1 source package rows (curl); 10 state rows across 10 repos (3.10-main, 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 10, open 0.	https://security.alpinelinux.org/vuln/CVE-2016-8616
`debian`	not yet assigned	CVE-2016-8616 not yet assigned priority: Debian including 1 source packages (curl), 5 status rows across 5 suites (bookworm, bullseye, forky, sid, trixie): resolved 5.	https://security-tracker.debian.org/tracker/CVE-2016-8616
`gentoo`	normal	CVE-2016-8616: 1 GLSA(s) (201701-47), 1 atom(s) (net-misc/curl); latest impact normal.	https://bugs.gentoo.org/buglist.cgi?quicksearch=CVE-2016-8616
`redhat`	low	—	https://access.redhat.com/security/cve/CVE-2016-8616
`suse`	low	CVE-2016-8616 severity low: SUSE including 334 source package names (0.9.1:libcurl4-7.37.0-31.1, 1.0.0:libcurl4-7.37.0-31.1, …), 397 product×package rows across 66 product lines (Container caasp/v4/default-http-backend, Container caasp/v4/dnsmasq-nanny, … (66 product lines)): Fixed 225, Known Affected 157, Known Not Affected 15.	https://www.suse.com/security/cve/CVE-2016-8616/
`ubuntu`	low	CVE-2016-8616 low priority: Ubuntu including 1 source packages (curl), 6 status rows across 6 suites (precise, trusty, upstream, xenial, yakkety, zesty): released 6.	https://ubuntu.com/security/CVE-2016-8616

Affected software / configurations for CVE-2016-8616

Vendor	Product	Version	Raw CPE
haxx	curl	< 7.51.0	cpe:2.3:a:haxx:curl::::::::

References for CVE-2016-8616

URL	Tags
http://www.oracle.com/technetwork/security-advisory/cpuoct2018-4428296.html	Patch
http://www.securityfocus.com/bid/94094	Third Party Advisory VDB Entry
http://www.securitytracker.com/id/1037192	Third Party Advisory VDB Entry
https://access.redhat.com/errata/RHSA-2018:2486	Third Party Advisory
https://access.redhat.com/errata/RHSA-2018:3558	Third Party Advisory
https://bugzilla.redhat.com/show_bug.cgi?id=CVE-2016-8616	Issue Tracking Patch Vendor Advisory
https://curl.haxx.se/CVE-2016-8616.patch	Patch Vendor Advisory
https://curl.haxx.se/docs/adv_20161102B.html	Patch Vendor Advisory
https://security.gentoo.org/glsa/201701-47	Third Party Advisory
https://www.tenable.com/security/tns-2016-21	Third Party Advisory

URL

CVE-2016-8616

Exploit prediction scoring system (EPSS) score for CVE-2016-8616

Common vulnerability scoring system (CVSS) metrics for CVE-2016-8616

Weakness enumeration for CVE-2016-8616

OS Trackers for CVE-2016-8616

Affected software / configurations for CVE-2016-8616

References for CVE-2016-8616