CVE.org (no NVD analysis yet)· CNA curl

CVE-2026-87865: knownhost callback mismatches key as missing

Noroxi assessment

Priority: Monitor (action score 29/100)

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: 0.60% (FIRST EPSS).
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: azl3 curl 8.11.1-12 on Azure Linux 3.0 Release Notes.

Low priority for now. Upgrade to azl3 curl 8.11.1-12 on Azure Linux 3.0 Release Notes 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

When libcurl uses libssh2 with a hashed `known_hosts` file, an unrelated initial entry can cause host key validation to report a key *mismatch* as a *missing* key to the `CURLOPT_SSH_KEYFUNCTION` callback.

HighCVSS 7.4 · v3.1—No exploit Fix available

Published: Oct 20, 2026
Updated: Oct 30, 2026
EPSS: 0.6% · 49th percentile
CWE: CWE-295

Report tools

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Action score

Monitor

Low priority for now.

CVSS: 29 / 40 · 7.4 / 10
CISA KEV: 0 / 30 · Not listed
EPSS: 0 / 30 · 0.6%

CISA SSVC decision

Exploitation: proof of concept
Automatable: no
Technical impact: total

Vulnrichment: CISA's decision-tree inputs.

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

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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?

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This vulnerability is about certificate validation or weak cryptography. The free SSL checker tests your certificate, enabled TLS versions and weak ciphers.

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Versions reported by the vendor

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

curl curl
- 8.22.0 and later · up to and including 8.22.0affected · semver
- 8.21.0 and later · up to and including 8.21.0affected · semver
- 8.20.0 and later · up to and including 8.20.0affected · semver
- 8.19.0 and later · up to and including 8.19.0affected · semver
- 8.18.0 and later · up to and including 8.18.0affected · semver
- 8.17.0 and later · up to and including 8.17.0affected · semver
- 8.16.0 and later · up to and including 8.16.0affected · semver
- 8.15.0 and later · up to and including 8.15.0affected · semver
- 8.14.1 and later · up to and including 8.14.1affected · semver
- 8.14.0 and later · up to and including 8.14.0affected · semver

Package-level exposure

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

Ecosystem	Package	Affected range	Fix
Alpine:v3.23	curl	before 8.23.0-r0	8.23.0-r0
Debian:12	curl	from 0	—
openSUSE:Tumbleweed	curl	before 8.23.0-1.1	8.23.0-1.1
Red Hat:hummingbird:1	curl	before 0:8.23.0-0.1.hum1	0:8.23.0-0.1.hum1
Red Hat:hummingbird:1	libcurl	before 0:8.23.0-0.1.hum1	0:8.23.0-0.1.hum1
Red Hat:hummingbird:1	libcurl-devel	before 0:8.23.0-0.1.hum1	0:8.23.0-0.1.hum1
Red Hat:hummingbird:1	libcurl-minimal	before 0:8.23.0-0.1.hum1	0:8.23.0-0.1.hum1

Same product

curl: all records

Other highest-scoring records for the same primary product.

CVE-2026-94265Authorization: Negotiate sent to foreign origin
36Monitor
CVE-2026-92388FTP wildcard write callback mixup
36Monitor
CVE-2026-87866wolfSSL public-key pinning bypass
36Monitor

Published before and after this one in the same product

← EarlierCVE-2026-87863Oct 20, 2026 · HSTS response erases persisted entries
32Monitor
← EarlierCVE-2026-87864Oct 20, 2026 · IMAP APPEND plus CRLF conversion command injection
32Monitor
Later →CVE-2026-92386Oct 20, 2026 · server-set cookie aborts cookie jar load
32Monitor

Remediation

Which version to upgrade to

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

Product / package	Fixed version	Source
azl3 curl 8.11.1-12 on Azure Linux 3.0	Release Notes	Microsoft (MSRC)
alpine:curl	8.23.0-r0 · Alpine:v3.23	Package registry (OSV)
opensuse:curl	8.23.0-1.1 · openSUSE:Tumbleweed	Package registry (OSV)
red hat:curl	0:8.23.0-0.1.hum1 · Red Hat:hummingbird:1	Package registry (OSV)
red hat:libcurl	0:8.23.0-0.1.hum1 · Red Hat:hummingbird:1	Package registry (OSV)
red hat:libcurl-devel	0:8.23.0-0.1.hum1 · Red Hat:hummingbird:1	Package registry (OSV)
red hat:libcurl-minimal	0:8.23.0-0.1.hum1 · Red Hat:hummingbird:1	Package 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.

PublishedOct 20, 2026
Fix recordedOct 21, 2026same day
TodayNov 10, 2026+21 d

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.

Bobbeh Rhinofinder

Variant candidates

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

CVE-2026-878660 days apartwolfSSL public-key pinning bypass
36Monitor

Chain candidates

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

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Bug bounty scope

The product’s vendor appears in a public program. Matched by name; verify the scope text in the 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: high · data or configuration can be modified
Availability: none

Attack vector: Network
Attack complexity: High
Privileges required: None
User interaction: None
Scope: Unchanged
Confidentiality impact: High
Integrity impact: High
Availability impact: None

Weakness class (CWE)

CWE-295 · Improper Certificate Validation

CVSS vector

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

nvd-secondary

Root cause

A certificate validation error is silently swallowed instead of terminating the connection. Often, code added for a test environment makes its way into production.

The bug in code

The whole CWE-295 class

A representative example of this vulnerability class. Not the vendor's source code; it shows the faulty pattern and its fix.

Vulnerable

kotlin

1override fun checkServerTrusted(chain: Array<X509Certificate>, type: String) {
2  // Left empty for the test environment
3}

Fixed

kotlin

1val client = OkHttpClient.Builder()
2  .certificatePinner(
3    CertificatePinner.Builder()
4      .add("api.sirius.example", "sha256/…")
5      .build()
6  ).build()

Attack context

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

Attack patterns (CAPEC)

ATT&CK techniques

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Change log

CVSS— → 7.4Oct 30, 2026, 2:07 PM UTC
Severity— → highOct 30, 2026, 2:07 PM UTC
SSVC exploitation— → pocOct 30, 2026, 2:07 PM UTC
Fix✗ → ✓Oct 21, 2026, 3:41 AM UTC
Exploit maturity— → noneOct 20, 2026, 10:07 PM UTC

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References

curl.se/docs/CVE-2026-87865.html

Show all references (2 more)

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

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