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CVE-2016-8622· NVD / CVE Program· CNA redhat

The URL percent-encoding decode function in libcurl before 7.51.0 is called `curl_easy_unescape`.

The URL percent-encoding decode function in libcurl before 7.51.0 is called `curl_easy_unescape`. Internally, even if this function would be made to allocate a unscape destination buffer larger than 2GB, it would return that new length in a signed 32 bit integer variable, thus the length would get either just truncated or both truncated and turned negative. That could then lead to libcurl writing outside of its heap based buffer.

CriticalCVSS 9.8 · v3.0—No exploit Fix available
Published
Jul 31, 2018
Updated
Jun 16, 2026
EPSS
4.7% · 91th percentile
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Report tools

JSON

Action score

40

Plan

Add it to your regular patch cycle.

CVSS
39 / 40 · 9.8 / 10
CISA KEV
0 / 30 · Not listed
EPSS
1 / 30 · 4.7%

CISA SSVC decision

Exploitation
none
Automatable
no
Technical impact
partial

Vulnrichment: CISA's decision-tree inputs.

CNA vs NVD score

NVD
9.8
CNA · redhat
3.7
6.1 point gap

CVSS:3.0/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:L/A:N

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

Affected systems

VendorProduct
haxxlibcurl

Affected versions

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

  • haxx libcurlbefore 7.51.0

Versions reported by the vendor

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

  • The Curl Project curl

    • 7.51.0affected

Package-level exposure

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

EcosystemPackageAffected rangeFix
Alpine:v3.10curlbefore 7.51.0-r07.51.0-r0
Alpine:v3.11curlbefore 7.51.07.51.0
Alpine:v3.2curlbefore 7.49.1-r47.49.1-r4
Debian:12curlbefore 7.51.0-17.51.0-1
Debian:7curlbefore 7.26.0-1+wheezy177.26.0-1+wheezy17
Debian:8curlbefore 7.38.0-4+deb8u57.38.0-4+deb8u5
Red Hat:rhel_software_collections:3::el6httpd24-curlbefore 0:7.61.1-1.el60:7.61.1-1.el6
Red Hat:rhel_software_collections:3::el6httpd24-curl-debuginfobefore 0:7.61.1-1.el60:7.61.1-1.el6
Red Hat:rhel_software_collections:3::el6httpd24-httpdbefore 0:2.4.34-7.el60:2.4.34-7.el6
Red Hat:rhel_software_collections:3::el6httpd24-httpd-debuginfobefore 0:2.4.34-7.el60:2.4.34-7.el6
Red Hat:rhel_software_collections:3::el6httpd24-httpd-develbefore 0:2.4.34-7.el60:2.4.34-7.el6
Red Hat:rhel_software_collections:3::el6httpd24-httpd-manualbefore 0:2.4.34-7.el60:2.4.34-7.el6
Red Hat:rhel_software_collections:3::el6httpd24-httpd-toolsbefore 0:2.4.34-7.el60:2.4.34-7.el6
Red Hat:rhel_software_collections:3::el6httpd24-libcurlbefore 0:7.61.1-1.el60:7.61.1-1.el6
Red Hat:rhel_software_collections:3::el6httpd24-libcurl-develbefore 0:7.61.1-1.el60:7.61.1-1.el6
Red Hat:rhel_software_collections:3::el6httpd24-libnghttp2before 0:1.7.1-7.el60:1.7.1-7.el6
Red Hat:rhel_software_collections:3::el6httpd24-libnghttp2-develbefore 0:1.7.1-7.el60:1.7.1-7.el6
Red Hat:rhel_software_collections:3::el6httpd24-mod_ldapbefore 0:2.4.34-7.el60:2.4.34-7.el6
Red Hat:rhel_software_collections:3::el6httpd24-mod_proxy_htmlbefore 1:2.4.34-7.el61:2.4.34-7.el6
Red Hat:rhel_software_collections:3::el6httpd24-mod_sessionbefore 0:2.4.34-7.el60:2.4.34-7.el6
Red Hat:rhel_software_collections:3::el6httpd24-mod_sslbefore 1:2.4.34-7.el61:2.4.34-7.el6
Red Hat:rhel_software_collections:3::el6httpd24-nghttp2before 0:1.7.1-7.el60:1.7.1-7.el6
Red Hat:rhel_software_collections:3::el6httpd24-nghttp2-debuginfobefore 0:1.7.1-7.el60:1.7.1-7.el6
Red Hat:rhel_software_collections:3::el7httpd24-curlbefore 0:7.61.1-1.el70:7.61.1-1.el7

+21

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.
    63This 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
  • CVE-2018-14618curl before version 7.61.1 is vulnerable to a buffer overrun in the NTLM authentication code.
    42Plan
  • CVE-2021-22945When 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 freed
    38Monitor
  • CVE-2017-1000257An IMAP FETCH response line indicates the size of the returned data, in number of bytes.
    38Monitor

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
alpine:curl7.51.0-r0 · Alpine:v3.10Package registry (OSV)
debian:curl7.51.0-1 · Debian:12Package registry (OSV)
red hat:httpd24-curl0:7.61.1-1.el6 · Red Hat:rhel_software_collections:3::el6Package registry (OSV)
red hat:httpd24-curl-debuginfo0:7.61.1-1.el6 · Red Hat:rhel_software_collections:3::el6Package registry (OSV)
red hat:httpd24-httpd0:2.4.34-7.el6 · Red Hat:rhel_software_collections:3::el6Package registry (OSV)
red hat:httpd24-httpd-debuginfo0:2.4.34-7.el6 · Red Hat:rhel_software_collections:3::el6Package registry (OSV)
red hat:httpd24-httpd-devel0:2.4.34-7.el6 · Red Hat:rhel_software_collections:3::el6Package registry (OSV)
red hat:httpd24-httpd-manual0:2.4.34-7.el6 · Red Hat:rhel_software_collections:3::el6Package registry (OSV)
red hat:httpd24-httpd-tools0:2.4.34-7.el6 · Red Hat:rhel_software_collections:3::el6Package registry (OSV)
red hat:httpd24-libcurl0:7.61.1-1.el6 · Red Hat:rhel_software_collections:3::el6Package registry (OSV)
red hat:httpd24-libcurl-devel0:7.61.1-1.el6 · Red Hat:rhel_software_collections:3::el6Package registry (OSV)
red hat:httpd24-libnghttp20:1.7.1-7.el6 · Red Hat:rhel_software_collections:3::el6Package registry (OSV)
red hat:httpd24-libnghttp2-devel0:1.7.1-7.el6 · Red Hat:rhel_software_collections:3::el6Package registry (OSV)
red hat:httpd24-mod_ldap0:2.4.34-7.el6 · Red Hat:rhel_software_collections:3::el6Package registry (OSV)
suse:curl7.37.0-31.1 · SUSE:Linux Enterprise Desktop 12 SP1Package registry (OSV)
suse:curl-openssl17.19.7-1.64.1 · SUSE:Linux Enterprise Server 11-SECURITYPackage registry (OSV)

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.

EPSS, last 120 days

FIRST EPSS daily score; only changes of 0.01 or more are recorded (step chart).

Patch and commit links

Commit, PR and diff links among the references. A starting point for patch-diffing and variant hunting; fixes, not exploits.

No commit or PR link among the references.

Credits

All researchers

Finders, reporters and analysts named in the CNA record. Click a name for that researcher’s other records.

No credits in the CNA record.

Variant candidates

Same product, same weakness class, within 18 months. If the patch missed the root cause, the sibling bug is here.

No nightly-computed relations.

Chain candidates

An authentication bypass and a privilege-requiring bug in the same product, published close together: combined they may become an unauthenticated path.

—

Bug bounty scope

No known public program.

Source: bounty-targets-data (public HackerOne, Bugcrowd, Intigriti, YesWeHack listings).

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.
  • No special conditions are required; it is repeatable.

If successful

Confidentiality
high · data can be read
Integrity
high · data or configuration can be modified
Availability
high · the service can be disrupted
Attack vector
Network
Attack complexity
Low
Privileges required
None
User interaction
None
Scope
Unchanged
Confidentiality impact
High
Integrity impact
High
Availability impact
High

Weakness class (CWE)

CWE-122 · Heap-based Buffer Overflow

CVSS vector

CVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H

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.

ATT&CK techniques

—

Noroxi analysis

No Noroxi analysis for this record yet

We don't hand-write analysis for all 385,000+ vulnerabilities; that wouldn't be honest. For notable, high-impact vulnerabilities our team writes the mechanism, detection and remediation steps.

We use this product, ask for help

Change log

  1. Fix✗ → ✓

For records you follow, these changes also arrive as notifications. →

References

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

All records