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NVD / CVE Program· CNA hackerone

CVE-2023-27535: An authentication bypass vulnerability exists in libcurl <8.0.0 in the FTP connection reuse feature that can result in wrong credentials…

MediumCVSS 5.9 · v3.1—No exploit Fix available

Noroxi assessment

Priority: Monitor (action score 24/100)

  • The sources we track (CISA KEV, Exploit-DB, Metasploit, Nuclei, GitHub) show no public exploit code or exploitation in the wild.
  • Probability of exploitation in the next 30 days: 1.8% (FIRST EPSS); higher than 78.8% of all records.
  • Anyone who can reach it over the internet can trigger it. No account or password is required. No user action is required. Special conditions such as timing or configuration are required.
  • Fixed version: Azure Linux 3.0 ARM 2.16.1-1, 3.28.2-1; Azure Linux 3.0 x64 2.16.1-1, 3.28.2-1; CBL Mariner 2.0 ARM 1.72.0-2, 3.21.4-13, 8.0.1-1.
  • Mentioned 1 time in Turkish national cyber security advisories (siberguvenlik.gov.tr).

Low priority for now. Upgrade to Azure Linux 3.0 ARM 2.16.1-1, 3.28.2-1; Azure Linux 3.0 x64 2.16.1-1, 3.28.2-1; CBL Mariner 2.0 ARM 1.72.0-2, 3.21.4-13, 8.0.1-1 or later.

Generated automatically from the record's data: CVSS (NVD and CNA), CISA KEV and SSVC, FIRST EPSS, exploit sources, fixed versions. How we calculate it

Primary sources: NVD · CVE.org · FIRST EPSS

An authentication bypass vulnerability exists in libcurl <8.0.0 in the FTP connection reuse feature that can result in wrong credentials being used during subsequent transfers. Previously created connections are kept in a connection pool for reuse if they match the current setup. However, certain FTP settings such as CURLOPT_FTP_ACCOUNT, CURLOPT_FTP_ALTERNATIVE_TO_USER, CURLOPT_FTP_SSL_CCC, and CURLOPT_USE_SSL were not included in the configuration match checks, causing them to match too easily. This could lead to libcurl using the wrong credentials when performing a transfer, potentially allowing unauthorized access to sensitive information.

Published
Mar 30, 2023
Updated
Oct 24, 2026
EPSS
1.8% · 78th percentile

Report tools

JSON

Action score

24

Monitor

Low priority for now.

CVSS
23 / 40 · 5.9 / 10
CISA KEV
0 / 30 · Not listed
EPSS
1 / 30 · 1.8%

CISA SSVC decision

Exploitation
proof of concept
Automatable
no
Technical impact
partial

Vulnrichment: CISA's decision-tree inputs.

CNA vs NVD score

NVD
5.9
CNA · hackerone
5.9
agree

The score given by the assigning authority versus NVD’s independent score. A gap means the severity is contested.

Get told when this record changes

  • Not in KEV: no record of exploitation in the wild
  • No public exploit code on record
  • A fix has been released

If any of these changes, we'll tell you in the daily email digest.

Follow CVE-2023-27535

When you'll hear from us

  • when it enters CISA KEV
  • when exploit code appears or is weaponized
  • when the record is updated (including a fixed version)
  • when EPSS rises 20 points in a week

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Noroxi analysis

What does it mean in your environment?

The assessment above is generated automatically from the record's data; it doesn't know your environment. Our team verifies on your systems whether this vulnerability is actually exploitable and which mitigation is enough.

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Affected systems

Is your version affected?

Pick the product and type the version you run. It's compared with this record's version ranges in your browser; the version isn't sent anywhere.

VendorProduct
haxxlibcurl
fedoraprojectfedora
debiandebian linux
netappactive iq unified manager
netappontap 9
netapph300s firmware
netapph300s
netapph500s firmware
netapph500s
netapph700s firmware
netapph700s
netapph410s firmware

and 2 more

Versions reported by the vendor

Affected version ranges reported by the assigning authority (hackerone). Independent of NVD's CPE analysis and usually ahead of it.

  • n/a https://github.com/curl/curl

    • Fixed in 8.0.0affected
Affected versions · NVD (12)

NVD version ranges (for catalog products). Add the product to your stack with a version and matching uses these.

  • debian debian linux10.0
  • fedoraproject fedora36
  • haxx libcurl7.13.0 and later · up to 7.88.1 inclusive
  • netapp active iq unified managerall versions
  • netapp h300s firmwareall versions
  • netapp h410s firmwareall versions
  • netapp h500s firmwareall versions
  • netapp h700s firmwareall versions
  • netapp ontap 9all versions
  • splunk universal forwarder8.2.0 and later · before 8.2.12
  • splunk universal forwarder9.0.0 and later · before 9.0.6
  • splunk universal forwarder9.1.0

Package-level exposure

OSV and GitHub Advisory data: ecosystem, package and range. SBOM matching uses this table.

EcosystemPackageAffected rangeFix
AlmaLinux:8curlbefore 7.61.1-30.el8_8.27.61.1-30.el8_8.2
AlmaLinux:8libcurlbefore 7.61.1-30.el8_8.27.61.1-30.el8_8.2
AlmaLinux:8libcurl-develbefore 7.61.1-30.el8_8.27.61.1-30.el8_8.2
AlmaLinux:8libcurl-minimalbefore 7.61.1-30.el8_8.27.61.1-30.el8_8.2
AlmaLinux:9curlbefore 7.76.1-23.el9_2.17.76.1-23.el9_2.1
AlmaLinux:9curl-minimalbefore 7.76.1-23.el9_2.17.76.1-23.el9_2.1
AlmaLinux:9libcurlbefore 7.76.1-23.el9_2.17.76.1-23.el9_2.1
AlmaLinux:9libcurl-develbefore 7.76.1-23.el9_2.17.76.1-23.el9_2.1
AlmaLinux:9libcurl-minimalbefore 7.76.1-23.el9_2.17.76.1-23.el9_2.1
Alpine:v3.14curlbefore 8.0.1-r08.0.1-r0
Alpine:v3.17curlbefore 7.88.1-r17.88.1-r1
Alpine:v3.18curlbefore 8.0.0-r08.0.0-r0
Debian:10curlbefore 7.64.0-4+deb10u67.64.0-4+deb10u6
Debian:12curlbefore 7.88.1-77.88.1-7
openSUSE:Leap Micro 5.3curlbefore 7.79.1-150400.5.18.17.79.1-150400.5.18.1
openSUSE:Tumbleweedcurlbefore 8.0.1-1.18.0.1-1.1
Red Hat:enterprise_linux:8::baseoscurlbefore 0:7.61.1-30.el8_8.20:7.61.1-30.el8_8.2
Red Hat:enterprise_linux:8::baseoscurl-debuginfobefore 0:7.61.1-30.el8_8.20:7.61.1-30.el8_8.2
Red Hat:enterprise_linux:8::baseoscurl-debugsourcebefore 0:7.61.1-30.el8_8.20:7.61.1-30.el8_8.2
Red Hat:enterprise_linux:8::baseoscurl-minimal-debuginfobefore 0:7.61.1-30.el8_8.20:7.61.1-30.el8_8.2
Red Hat:enterprise_linux:8::baseoslibcurlbefore 0:7.61.1-30.el8_8.20:7.61.1-30.el8_8.2
Red Hat:enterprise_linux:8::baseoslibcurl-debuginfobefore 0:7.61.1-30.el8_8.20:7.61.1-30.el8_8.2
Red Hat:enterprise_linux:8::baseoslibcurl-develbefore 0:7.61.1-30.el8_8.20:7.61.1-30.el8_8.2
Red Hat:enterprise_linux:8::baseoslibcurl-minimalbefore 0:7.61.1-30.el8_8.20:7.61.1-30.el8_8.2

+26

Same product

haxx: all records

Other highest-scoring records for the same primary product.

  • CVE-2023-38545This flaw makes curl overflow a heap based buffer in the SOCKS5 proxy handshake.
    62This week
  • CVE-2019-5436A heap buffer overflow in the TFTP receiving code allows for DoS or arbitrary code execution in libcurl versions 7.19.4 through 7.64.1.
    46Plan
  • CVE-2019-3822libcurl versions from 7.36.0 to before 7.64.0 are vulnerable to a stack-based buffer overflow.
    43Plan

Published before and after this one in the same product

  • ← EarlierCVE-2021-22924Aug 5, 2021 · libcurl keeps previously used connections in a connection pool for subsequenttransfers to reuse, if one of them matches the setup.Due to…
    16Monitor
  • ← EarlierCVE-2021-22945Sep 23, 2021 · When sending data to an MQTT server, libcurl <= 7.73.0 and 7.78.0 could in some circumstances erroneously keep a pointer to an already…
    38Monitor
  • Later →CVE-2023-27536Mar 30, 2023 · An authentication bypass vulnerability exists libcurl <8.0.0 in the connection reuse feature which can reuse previously established…
    24Monitor

Remediation

Which version to upgrade to

Fix versions compiled from the vendor, package registries and Microsoft. Verify the vendor's note before upgrading.

Product / packageFixed versionSource
Azure Linux 3.0 ARM2.16.1-1 · tensorflowMicrosoft (MSRC)
Azure Linux 3.0 ARM3.28.2-1 · cmakeMicrosoft (MSRC)
Azure Linux 3.0 x642.16.1-1 · tensorflowMicrosoft (MSRC)
Azure Linux 3.0 x643.28.2-1 · cmakeMicrosoft (MSRC)
CBL Mariner 2.0 ARM1.72.0-2 · rustMicrosoft (MSRC)
CBL Mariner 2.0 ARM3.21.4-13 · cmakeMicrosoft (MSRC)
CBL Mariner 2.0 ARM8.0.1-1 · curlMicrosoft (MSRC)
CBL Mariner 2.0 ARM8.0.34-1 · mysqlMicrosoft (MSRC)
CBL Mariner 2.0 x641.72.0-2 · rustMicrosoft (MSRC)
CBL Mariner 2.0 x643.21.4-13 · cmakeMicrosoft (MSRC)
CBL Mariner 2.0 x648.0.1-1 · curlMicrosoft (MSRC)
CBL Mariner 2.0 x648.0.34-1 · mysqlMicrosoft (MSRC)
almalinux:curl7.76.1-23.el9_2.1 · AlmaLinux:9Package registry (OSV)
almalinux:curl-minimal7.76.1-23.el9_2.1 · AlmaLinux:9Package registry (OSV)
almalinux:libcurl7.76.1-23.el9_2.1 · AlmaLinux:9Package registry (OSV)
almalinux:libcurl-devel7.76.1-23.el9_2.1 · AlmaLinux:9Package registry (OSV)
almalinux:libcurl-minimal7.76.1-23.el9_2.1 · AlmaLinux:9Package registry (OSV)
alpine:curl8.0.1-r0 · Alpine:v3.14Package registry (OSV)
debian:curl7.88.1-7 · Debian:12Package registry (OSV)
opensuse:curl7.79.1-150400.5.18.1 · openSUSE:Leap Micro 5.3Package registry (OSV)
red hat:curl0:7.76.1-23.el9_2.1 · Red Hat:enterprise_linux:9::baseosPackage registry (OSV)
red hat:curl-debuginfo0:7.76.1-23.el9_2.1 · Red Hat:enterprise_linux:9::appstreamPackage registry (OSV)
red hat:curl-debugsource0:7.76.1-23.el9_2.1 · Red Hat:enterprise_linux:9::appstreamPackage registry (OSV)
red hat:curl-minimal0:7.76.1-23.el9_2.1 · Red Hat:enterprise_linux:9::baseosPackage registry (OSV)
red hat:curl-minimal-debuginfo0:7.76.1-23.el9_2.1 · Red Hat:enterprise_linux:9::appstreamPackage registry (OSV)
red hat:libcurl0:7.76.1-23.el9_2.1 · Red Hat:enterprise_linux:9::baseosPackage registry (OSV)
red hat:libcurl-debuginfo0:7.76.1-23.el9_2.1 · Red Hat:enterprise_linux:9::appstreamPackage registry (OSV)
red hat:libcurl-devel0:7.76.1-23.el9_2.1 · Red Hat:enterprise_linux:9::appstreamPackage registry (OSV)
red hat:libcurl-minimal0:7.76.1-23.el9_2.1 · Red Hat:enterprise_linux:9::baseosPackage registry (OSV)
red hat:libcurl-minimal-debuginfo0:7.76.1-23.el9_2.1 · Red Hat:enterprise_linux:9::appstreamPackage registry (OSV)

+3

Exploit status

No known public exploit

No public exploit has been observed yet. That doesn't mean you're safe, only that the bar is a little higher.

Research context

For pentesters and researchers: attack profile, score disagreement, timeline, patch commits, credits, variant and chain candidates, bug bounty scope. All derived from existing data; no exploit code.

Timeline

From publication to today: proof of concept, Metasploit module, CISA KEV and fix record. Dates are as reported by the sources.

No dated events beyond publication.

National notice (Türkiye Cybersecurity Directorate / USOM)

Official security notices citing this record; remediation advice is on the agency's page.

All national notices →

Not on record for this CVE: EPSS history · patch commit or PR link · researcher credit · variant or chain candidate · public bounty program.

Technical details

Attack conditions

  • Anyone who can reach it over the internet can trigger it.
  • No account or password is required.
  • No user action is required.
  • Special conditions such as timing or configuration are required.

If successful

Confidentiality
high · data can be read
Integrity
none
Availability
none
Attack vector
Network
Attack complexity
High
Privileges required
None
User interaction
None
Scope
Unchanged
Confidentiality impact
High
Integrity impact
None
Availability impact
None

Weakness class (CWE)

CWE-305 · Authentication Bypass by Primary Weakness

CVSS vector

CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:N/A:N

nvd-primary

Attack context

MITRE CAPEC attack patterns and ATT&CK techniques for this weakness class (CWE). A starting point for detection rules and threat hunting.

MITRE has no CAPEC/ATT&CK mapping for this CWE.

References

Show all references (6 more)

Vendor advisories and official records. Exploit/PoC links are deliberately left out.

All records